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b6520c8193
Make sure that comments describe what's going on and not how, and always use __d_instantiate instead of two separate branches, one with d_instantiate and one with __d_instantiate. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2352 lines
59 KiB
C
2352 lines
59 KiB
C
/*
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* fs/dcache.c
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*
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* Complete reimplementation
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* (C) 1997 Thomas Schoebel-Theuer,
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* with heavy changes by Linus Torvalds
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*/
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/*
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* Notes on the allocation strategy:
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*
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* The dcache is a master of the icache - whenever a dcache entry
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* exists, the inode will always exist. "iput()" is done either when
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* the dcache entry is deleted or garbage collected.
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*/
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#include <linux/syscalls.h>
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#include <linux/string.h>
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#include <linux/mm.h>
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#include <linux/fdtable.h>
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#include <linux/fs.h>
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#include <linux/fsnotify.h>
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#include <linux/slab.h>
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#include <linux/init.h>
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#include <linux/hash.h>
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#include <linux/cache.h>
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#include <linux/module.h>
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#include <linux/mount.h>
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#include <linux/file.h>
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#include <asm/uaccess.h>
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#include <linux/security.h>
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#include <linux/seqlock.h>
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#include <linux/swap.h>
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#include <linux/bootmem.h>
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#include "internal.h"
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int sysctl_vfs_cache_pressure __read_mostly = 100;
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EXPORT_SYMBOL_GPL(sysctl_vfs_cache_pressure);
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__cacheline_aligned_in_smp DEFINE_SPINLOCK(dcache_lock);
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__cacheline_aligned_in_smp DEFINE_SEQLOCK(rename_lock);
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EXPORT_SYMBOL(dcache_lock);
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static struct kmem_cache *dentry_cache __read_mostly;
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#define DNAME_INLINE_LEN (sizeof(struct dentry)-offsetof(struct dentry,d_iname))
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/*
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* This is the single most critical data structure when it comes
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* to the dcache: the hashtable for lookups. Somebody should try
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* to make this good - I've just made it work.
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*
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* This hash-function tries to avoid losing too many bits of hash
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* information, yet avoid using a prime hash-size or similar.
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*/
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#define D_HASHBITS d_hash_shift
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#define D_HASHMASK d_hash_mask
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static unsigned int d_hash_mask __read_mostly;
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static unsigned int d_hash_shift __read_mostly;
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static struct hlist_head *dentry_hashtable __read_mostly;
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/* Statistics gathering. */
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struct dentry_stat_t dentry_stat = {
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.age_limit = 45,
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};
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static void __d_free(struct dentry *dentry)
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{
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WARN_ON(!list_empty(&dentry->d_alias));
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if (dname_external(dentry))
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kfree(dentry->d_name.name);
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kmem_cache_free(dentry_cache, dentry);
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}
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static void d_callback(struct rcu_head *head)
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{
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struct dentry * dentry = container_of(head, struct dentry, d_u.d_rcu);
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__d_free(dentry);
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}
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/*
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* no dcache_lock, please. The caller must decrement dentry_stat.nr_dentry
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* inside dcache_lock.
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*/
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static void d_free(struct dentry *dentry)
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{
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if (dentry->d_op && dentry->d_op->d_release)
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dentry->d_op->d_release(dentry);
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/* if dentry was never inserted into hash, immediate free is OK */
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if (hlist_unhashed(&dentry->d_hash))
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__d_free(dentry);
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else
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call_rcu(&dentry->d_u.d_rcu, d_callback);
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}
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/*
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* Release the dentry's inode, using the filesystem
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* d_iput() operation if defined.
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*/
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static void dentry_iput(struct dentry * dentry)
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__releases(dentry->d_lock)
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__releases(dcache_lock)
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{
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struct inode *inode = dentry->d_inode;
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if (inode) {
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dentry->d_inode = NULL;
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list_del_init(&dentry->d_alias);
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spin_unlock(&dentry->d_lock);
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spin_unlock(&dcache_lock);
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if (!inode->i_nlink)
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fsnotify_inoderemove(inode);
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if (dentry->d_op && dentry->d_op->d_iput)
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dentry->d_op->d_iput(dentry, inode);
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else
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iput(inode);
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} else {
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spin_unlock(&dentry->d_lock);
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spin_unlock(&dcache_lock);
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}
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}
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/*
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* dentry_lru_(add|add_tail|del|del_init) must be called with dcache_lock held.
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*/
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static void dentry_lru_add(struct dentry *dentry)
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{
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list_add(&dentry->d_lru, &dentry->d_sb->s_dentry_lru);
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dentry->d_sb->s_nr_dentry_unused++;
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dentry_stat.nr_unused++;
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}
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static void dentry_lru_add_tail(struct dentry *dentry)
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{
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list_add_tail(&dentry->d_lru, &dentry->d_sb->s_dentry_lru);
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dentry->d_sb->s_nr_dentry_unused++;
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dentry_stat.nr_unused++;
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}
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static void dentry_lru_del(struct dentry *dentry)
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{
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if (!list_empty(&dentry->d_lru)) {
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list_del(&dentry->d_lru);
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dentry->d_sb->s_nr_dentry_unused--;
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dentry_stat.nr_unused--;
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}
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}
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static void dentry_lru_del_init(struct dentry *dentry)
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{
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if (likely(!list_empty(&dentry->d_lru))) {
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list_del_init(&dentry->d_lru);
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dentry->d_sb->s_nr_dentry_unused--;
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dentry_stat.nr_unused--;
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}
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}
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/**
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* d_kill - kill dentry and return parent
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* @dentry: dentry to kill
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*
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* The dentry must already be unhashed and removed from the LRU.
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*
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* If this is the root of the dentry tree, return NULL.
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*/
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static struct dentry *d_kill(struct dentry *dentry)
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__releases(dentry->d_lock)
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__releases(dcache_lock)
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{
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struct dentry *parent;
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list_del(&dentry->d_u.d_child);
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dentry_stat.nr_dentry--; /* For d_free, below */
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/*drops the locks, at that point nobody can reach this dentry */
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dentry_iput(dentry);
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if (IS_ROOT(dentry))
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parent = NULL;
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else
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parent = dentry->d_parent;
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d_free(dentry);
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return parent;
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}
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/*
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* This is dput
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*
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* This is complicated by the fact that we do not want to put
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* dentries that are no longer on any hash chain on the unused
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* list: we'd much rather just get rid of them immediately.
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*
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* However, that implies that we have to traverse the dentry
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* tree upwards to the parents which might _also_ now be
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* scheduled for deletion (it may have been only waiting for
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* its last child to go away).
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*
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* This tail recursion is done by hand as we don't want to depend
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* on the compiler to always get this right (gcc generally doesn't).
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* Real recursion would eat up our stack space.
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*/
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/*
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* dput - release a dentry
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* @dentry: dentry to release
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*
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* Release a dentry. This will drop the usage count and if appropriate
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* call the dentry unlink method as well as removing it from the queues and
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* releasing its resources. If the parent dentries were scheduled for release
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* they too may now get deleted.
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*
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* no dcache lock, please.
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*/
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void dput(struct dentry *dentry)
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{
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if (!dentry)
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return;
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repeat:
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if (atomic_read(&dentry->d_count) == 1)
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might_sleep();
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if (!atomic_dec_and_lock(&dentry->d_count, &dcache_lock))
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return;
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spin_lock(&dentry->d_lock);
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if (atomic_read(&dentry->d_count)) {
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spin_unlock(&dentry->d_lock);
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spin_unlock(&dcache_lock);
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return;
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}
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/*
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* AV: ->d_delete() is _NOT_ allowed to block now.
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*/
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if (dentry->d_op && dentry->d_op->d_delete) {
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if (dentry->d_op->d_delete(dentry))
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goto unhash_it;
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}
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/* Unreachable? Get rid of it */
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if (d_unhashed(dentry))
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goto kill_it;
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if (list_empty(&dentry->d_lru)) {
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dentry->d_flags |= DCACHE_REFERENCED;
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dentry_lru_add(dentry);
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}
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spin_unlock(&dentry->d_lock);
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spin_unlock(&dcache_lock);
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return;
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unhash_it:
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__d_drop(dentry);
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kill_it:
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/* if dentry was on the d_lru list delete it from there */
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dentry_lru_del(dentry);
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dentry = d_kill(dentry);
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if (dentry)
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goto repeat;
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}
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/**
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* d_invalidate - invalidate a dentry
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* @dentry: dentry to invalidate
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*
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* Try to invalidate the dentry if it turns out to be
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* possible. If there are other dentries that can be
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* reached through this one we can't delete it and we
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* return -EBUSY. On success we return 0.
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*
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* no dcache lock.
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*/
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int d_invalidate(struct dentry * dentry)
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{
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/*
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* If it's already been dropped, return OK.
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*/
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spin_lock(&dcache_lock);
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if (d_unhashed(dentry)) {
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spin_unlock(&dcache_lock);
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return 0;
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}
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/*
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* Check whether to do a partial shrink_dcache
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* to get rid of unused child entries.
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*/
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if (!list_empty(&dentry->d_subdirs)) {
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spin_unlock(&dcache_lock);
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shrink_dcache_parent(dentry);
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spin_lock(&dcache_lock);
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}
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/*
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* Somebody else still using it?
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*
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* If it's a directory, we can't drop it
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* for fear of somebody re-populating it
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* with children (even though dropping it
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* would make it unreachable from the root,
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* we might still populate it if it was a
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* working directory or similar).
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*/
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spin_lock(&dentry->d_lock);
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if (atomic_read(&dentry->d_count) > 1) {
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if (dentry->d_inode && S_ISDIR(dentry->d_inode->i_mode)) {
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spin_unlock(&dentry->d_lock);
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spin_unlock(&dcache_lock);
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return -EBUSY;
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}
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}
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__d_drop(dentry);
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spin_unlock(&dentry->d_lock);
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spin_unlock(&dcache_lock);
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return 0;
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}
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/* This should be called _only_ with dcache_lock held */
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static inline struct dentry * __dget_locked(struct dentry *dentry)
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{
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atomic_inc(&dentry->d_count);
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dentry_lru_del_init(dentry);
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return dentry;
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}
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struct dentry * dget_locked(struct dentry *dentry)
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{
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return __dget_locked(dentry);
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}
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/**
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* d_find_alias - grab a hashed alias of inode
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* @inode: inode in question
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* @want_discon: flag, used by d_splice_alias, to request
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* that only a DISCONNECTED alias be returned.
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*
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* If inode has a hashed alias, or is a directory and has any alias,
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* acquire the reference to alias and return it. Otherwise return NULL.
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* Notice that if inode is a directory there can be only one alias and
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* it can be unhashed only if it has no children, or if it is the root
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* of a filesystem.
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*
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* If the inode has an IS_ROOT, DCACHE_DISCONNECTED alias, then prefer
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* any other hashed alias over that one unless @want_discon is set,
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* in which case only return an IS_ROOT, DCACHE_DISCONNECTED alias.
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*/
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static struct dentry * __d_find_alias(struct inode *inode, int want_discon)
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{
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struct list_head *head, *next, *tmp;
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struct dentry *alias, *discon_alias=NULL;
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head = &inode->i_dentry;
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next = inode->i_dentry.next;
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while (next != head) {
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tmp = next;
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next = tmp->next;
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prefetch(next);
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alias = list_entry(tmp, struct dentry, d_alias);
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if (S_ISDIR(inode->i_mode) || !d_unhashed(alias)) {
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if (IS_ROOT(alias) &&
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(alias->d_flags & DCACHE_DISCONNECTED))
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discon_alias = alias;
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else if (!want_discon) {
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__dget_locked(alias);
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return alias;
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}
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}
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}
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if (discon_alias)
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__dget_locked(discon_alias);
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return discon_alias;
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}
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struct dentry * d_find_alias(struct inode *inode)
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{
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struct dentry *de = NULL;
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if (!list_empty(&inode->i_dentry)) {
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spin_lock(&dcache_lock);
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de = __d_find_alias(inode, 0);
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spin_unlock(&dcache_lock);
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}
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return de;
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}
|
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|
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/*
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* Try to kill dentries associated with this inode.
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* WARNING: you must own a reference to inode.
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*/
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void d_prune_aliases(struct inode *inode)
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{
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struct dentry *dentry;
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restart:
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spin_lock(&dcache_lock);
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list_for_each_entry(dentry, &inode->i_dentry, d_alias) {
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spin_lock(&dentry->d_lock);
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if (!atomic_read(&dentry->d_count)) {
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__dget_locked(dentry);
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__d_drop(dentry);
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spin_unlock(&dentry->d_lock);
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spin_unlock(&dcache_lock);
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dput(dentry);
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goto restart;
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}
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spin_unlock(&dentry->d_lock);
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}
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spin_unlock(&dcache_lock);
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}
|
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|
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/*
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* Throw away a dentry - free the inode, dput the parent. This requires that
|
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* the LRU list has already been removed.
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*
|
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* Try to prune ancestors as well. This is necessary to prevent
|
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* quadratic behavior of shrink_dcache_parent(), but is also expected
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* to be beneficial in reducing dentry cache fragmentation.
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*/
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static void prune_one_dentry(struct dentry * dentry)
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__releases(dentry->d_lock)
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__releases(dcache_lock)
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__acquires(dcache_lock)
|
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{
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__d_drop(dentry);
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dentry = d_kill(dentry);
|
|
|
|
/*
|
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* Prune ancestors. Locking is simpler than in dput(),
|
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* because dcache_lock needs to be taken anyway.
|
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*/
|
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spin_lock(&dcache_lock);
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while (dentry) {
|
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if (!atomic_dec_and_lock(&dentry->d_count, &dentry->d_lock))
|
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return;
|
|
|
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if (dentry->d_op && dentry->d_op->d_delete)
|
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dentry->d_op->d_delete(dentry);
|
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dentry_lru_del_init(dentry);
|
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__d_drop(dentry);
|
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dentry = d_kill(dentry);
|
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spin_lock(&dcache_lock);
|
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}
|
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}
|
|
|
|
/*
|
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* Shrink the dentry LRU on a given superblock.
|
|
* @sb : superblock to shrink dentry LRU.
|
|
* @count: If count is NULL, we prune all dentries on superblock.
|
|
* @flags: If flags is non-zero, we need to do special processing based on
|
|
* which flags are set. This means we don't need to maintain multiple
|
|
* similar copies of this loop.
|
|
*/
|
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static void __shrink_dcache_sb(struct super_block *sb, int *count, int flags)
|
|
{
|
|
LIST_HEAD(referenced);
|
|
LIST_HEAD(tmp);
|
|
struct dentry *dentry;
|
|
int cnt = 0;
|
|
|
|
BUG_ON(!sb);
|
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BUG_ON((flags & DCACHE_REFERENCED) && count == NULL);
|
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spin_lock(&dcache_lock);
|
|
if (count != NULL)
|
|
/* called from prune_dcache() and shrink_dcache_parent() */
|
|
cnt = *count;
|
|
restart:
|
|
if (count == NULL)
|
|
list_splice_init(&sb->s_dentry_lru, &tmp);
|
|
else {
|
|
while (!list_empty(&sb->s_dentry_lru)) {
|
|
dentry = list_entry(sb->s_dentry_lru.prev,
|
|
struct dentry, d_lru);
|
|
BUG_ON(dentry->d_sb != sb);
|
|
|
|
spin_lock(&dentry->d_lock);
|
|
/*
|
|
* If we are honouring the DCACHE_REFERENCED flag and
|
|
* the dentry has this flag set, don't free it. Clear
|
|
* the flag and put it back on the LRU.
|
|
*/
|
|
if ((flags & DCACHE_REFERENCED)
|
|
&& (dentry->d_flags & DCACHE_REFERENCED)) {
|
|
dentry->d_flags &= ~DCACHE_REFERENCED;
|
|
list_move_tail(&dentry->d_lru, &referenced);
|
|
spin_unlock(&dentry->d_lock);
|
|
} else {
|
|
list_move_tail(&dentry->d_lru, &tmp);
|
|
spin_unlock(&dentry->d_lock);
|
|
cnt--;
|
|
if (!cnt)
|
|
break;
|
|
}
|
|
cond_resched_lock(&dcache_lock);
|
|
}
|
|
}
|
|
while (!list_empty(&tmp)) {
|
|
dentry = list_entry(tmp.prev, struct dentry, d_lru);
|
|
dentry_lru_del_init(dentry);
|
|
spin_lock(&dentry->d_lock);
|
|
/*
|
|
* We found an inuse dentry which was not removed from
|
|
* the LRU because of laziness during lookup. Do not free
|
|
* it - just keep it off the LRU list.
|
|
*/
|
|
if (atomic_read(&dentry->d_count)) {
|
|
spin_unlock(&dentry->d_lock);
|
|
continue;
|
|
}
|
|
prune_one_dentry(dentry);
|
|
/* dentry->d_lock was dropped in prune_one_dentry() */
|
|
cond_resched_lock(&dcache_lock);
|
|
}
|
|
if (count == NULL && !list_empty(&sb->s_dentry_lru))
|
|
goto restart;
|
|
if (count != NULL)
|
|
*count = cnt;
|
|
if (!list_empty(&referenced))
|
|
list_splice(&referenced, &sb->s_dentry_lru);
|
|
spin_unlock(&dcache_lock);
|
|
}
|
|
|
|
/**
|
|
* prune_dcache - shrink the dcache
|
|
* @count: number of entries to try to free
|
|
*
|
|
* Shrink the dcache. This is done when we need more memory, or simply when we
|
|
* need to unmount something (at which point we need to unuse all dentries).
|
|
*
|
|
* This function may fail to free any resources if all the dentries are in use.
|
|
*/
|
|
static void prune_dcache(int count)
|
|
{
|
|
struct super_block *sb;
|
|
int w_count;
|
|
int unused = dentry_stat.nr_unused;
|
|
int prune_ratio;
|
|
int pruned;
|
|
|
|
if (unused == 0 || count == 0)
|
|
return;
|
|
spin_lock(&dcache_lock);
|
|
restart:
|
|
if (count >= unused)
|
|
prune_ratio = 1;
|
|
else
|
|
prune_ratio = unused / count;
|
|
spin_lock(&sb_lock);
|
|
list_for_each_entry(sb, &super_blocks, s_list) {
|
|
if (sb->s_nr_dentry_unused == 0)
|
|
continue;
|
|
sb->s_count++;
|
|
/* Now, we reclaim unused dentrins with fairness.
|
|
* We reclaim them same percentage from each superblock.
|
|
* We calculate number of dentries to scan on this sb
|
|
* as follows, but the implementation is arranged to avoid
|
|
* overflows:
|
|
* number of dentries to scan on this sb =
|
|
* count * (number of dentries on this sb /
|
|
* number of dentries in the machine)
|
|
*/
|
|
spin_unlock(&sb_lock);
|
|
if (prune_ratio != 1)
|
|
w_count = (sb->s_nr_dentry_unused / prune_ratio) + 1;
|
|
else
|
|
w_count = sb->s_nr_dentry_unused;
|
|
pruned = w_count;
|
|
/*
|
|
* We need to be sure this filesystem isn't being unmounted,
|
|
* otherwise we could race with generic_shutdown_super(), and
|
|
* end up holding a reference to an inode while the filesystem
|
|
* is unmounted. So we try to get s_umount, and make sure
|
|
* s_root isn't NULL.
|
|
*/
|
|
if (down_read_trylock(&sb->s_umount)) {
|
|
if ((sb->s_root != NULL) &&
|
|
(!list_empty(&sb->s_dentry_lru))) {
|
|
spin_unlock(&dcache_lock);
|
|
__shrink_dcache_sb(sb, &w_count,
|
|
DCACHE_REFERENCED);
|
|
pruned -= w_count;
|
|
spin_lock(&dcache_lock);
|
|
}
|
|
up_read(&sb->s_umount);
|
|
}
|
|
spin_lock(&sb_lock);
|
|
count -= pruned;
|
|
/*
|
|
* restart only when sb is no longer on the list and
|
|
* we have more work to do.
|
|
*/
|
|
if (__put_super_and_need_restart(sb) && count > 0) {
|
|
spin_unlock(&sb_lock);
|
|
goto restart;
|
|
}
|
|
}
|
|
spin_unlock(&sb_lock);
|
|
spin_unlock(&dcache_lock);
|
|
}
|
|
|
|
/**
|
|
* shrink_dcache_sb - shrink dcache for a superblock
|
|
* @sb: superblock
|
|
*
|
|
* Shrink the dcache for the specified super block. This
|
|
* is used to free the dcache before unmounting a file
|
|
* system
|
|
*/
|
|
void shrink_dcache_sb(struct super_block * sb)
|
|
{
|
|
__shrink_dcache_sb(sb, NULL, 0);
|
|
}
|
|
|
|
/*
|
|
* destroy a single subtree of dentries for unmount
|
|
* - see the comments on shrink_dcache_for_umount() for a description of the
|
|
* locking
|
|
*/
|
|
static void shrink_dcache_for_umount_subtree(struct dentry *dentry)
|
|
{
|
|
struct dentry *parent;
|
|
unsigned detached = 0;
|
|
|
|
BUG_ON(!IS_ROOT(dentry));
|
|
|
|
/* detach this root from the system */
|
|
spin_lock(&dcache_lock);
|
|
dentry_lru_del_init(dentry);
|
|
__d_drop(dentry);
|
|
spin_unlock(&dcache_lock);
|
|
|
|
for (;;) {
|
|
/* descend to the first leaf in the current subtree */
|
|
while (!list_empty(&dentry->d_subdirs)) {
|
|
struct dentry *loop;
|
|
|
|
/* this is a branch with children - detach all of them
|
|
* from the system in one go */
|
|
spin_lock(&dcache_lock);
|
|
list_for_each_entry(loop, &dentry->d_subdirs,
|
|
d_u.d_child) {
|
|
dentry_lru_del_init(loop);
|
|
__d_drop(loop);
|
|
cond_resched_lock(&dcache_lock);
|
|
}
|
|
spin_unlock(&dcache_lock);
|
|
|
|
/* move to the first child */
|
|
dentry = list_entry(dentry->d_subdirs.next,
|
|
struct dentry, d_u.d_child);
|
|
}
|
|
|
|
/* consume the dentries from this leaf up through its parents
|
|
* until we find one with children or run out altogether */
|
|
do {
|
|
struct inode *inode;
|
|
|
|
if (atomic_read(&dentry->d_count) != 0) {
|
|
printk(KERN_ERR
|
|
"BUG: Dentry %p{i=%lx,n=%s}"
|
|
" still in use (%d)"
|
|
" [unmount of %s %s]\n",
|
|
dentry,
|
|
dentry->d_inode ?
|
|
dentry->d_inode->i_ino : 0UL,
|
|
dentry->d_name.name,
|
|
atomic_read(&dentry->d_count),
|
|
dentry->d_sb->s_type->name,
|
|
dentry->d_sb->s_id);
|
|
BUG();
|
|
}
|
|
|
|
if (IS_ROOT(dentry))
|
|
parent = NULL;
|
|
else {
|
|
parent = dentry->d_parent;
|
|
atomic_dec(&parent->d_count);
|
|
}
|
|
|
|
list_del(&dentry->d_u.d_child);
|
|
detached++;
|
|
|
|
inode = dentry->d_inode;
|
|
if (inode) {
|
|
dentry->d_inode = NULL;
|
|
list_del_init(&dentry->d_alias);
|
|
if (dentry->d_op && dentry->d_op->d_iput)
|
|
dentry->d_op->d_iput(dentry, inode);
|
|
else
|
|
iput(inode);
|
|
}
|
|
|
|
d_free(dentry);
|
|
|
|
/* finished when we fall off the top of the tree,
|
|
* otherwise we ascend to the parent and move to the
|
|
* next sibling if there is one */
|
|
if (!parent)
|
|
goto out;
|
|
|
|
dentry = parent;
|
|
|
|
} while (list_empty(&dentry->d_subdirs));
|
|
|
|
dentry = list_entry(dentry->d_subdirs.next,
|
|
struct dentry, d_u.d_child);
|
|
}
|
|
out:
|
|
/* several dentries were freed, need to correct nr_dentry */
|
|
spin_lock(&dcache_lock);
|
|
dentry_stat.nr_dentry -= detached;
|
|
spin_unlock(&dcache_lock);
|
|
}
|
|
|
|
/*
|
|
* destroy the dentries attached to a superblock on unmounting
|
|
* - we don't need to use dentry->d_lock, and only need dcache_lock when
|
|
* removing the dentry from the system lists and hashes because:
|
|
* - the superblock is detached from all mountings and open files, so the
|
|
* dentry trees will not be rearranged by the VFS
|
|
* - s_umount is write-locked, so the memory pressure shrinker will ignore
|
|
* any dentries belonging to this superblock that it comes across
|
|
* - the filesystem itself is no longer permitted to rearrange the dentries
|
|
* in this superblock
|
|
*/
|
|
void shrink_dcache_for_umount(struct super_block *sb)
|
|
{
|
|
struct dentry *dentry;
|
|
|
|
if (down_read_trylock(&sb->s_umount))
|
|
BUG();
|
|
|
|
dentry = sb->s_root;
|
|
sb->s_root = NULL;
|
|
atomic_dec(&dentry->d_count);
|
|
shrink_dcache_for_umount_subtree(dentry);
|
|
|
|
while (!hlist_empty(&sb->s_anon)) {
|
|
dentry = hlist_entry(sb->s_anon.first, struct dentry, d_hash);
|
|
shrink_dcache_for_umount_subtree(dentry);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Search for at least 1 mount point in the dentry's subdirs.
|
|
* We descend to the next level whenever the d_subdirs
|
|
* list is non-empty and continue searching.
|
|
*/
|
|
|
|
/**
|
|
* have_submounts - check for mounts over a dentry
|
|
* @parent: dentry to check.
|
|
*
|
|
* Return true if the parent or its subdirectories contain
|
|
* a mount point
|
|
*/
|
|
|
|
int have_submounts(struct dentry *parent)
|
|
{
|
|
struct dentry *this_parent = parent;
|
|
struct list_head *next;
|
|
|
|
spin_lock(&dcache_lock);
|
|
if (d_mountpoint(parent))
|
|
goto positive;
|
|
repeat:
|
|
next = this_parent->d_subdirs.next;
|
|
resume:
|
|
while (next != &this_parent->d_subdirs) {
|
|
struct list_head *tmp = next;
|
|
struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child);
|
|
next = tmp->next;
|
|
/* Have we found a mount point ? */
|
|
if (d_mountpoint(dentry))
|
|
goto positive;
|
|
if (!list_empty(&dentry->d_subdirs)) {
|
|
this_parent = dentry;
|
|
goto repeat;
|
|
}
|
|
}
|
|
/*
|
|
* All done at this level ... ascend and resume the search.
|
|
*/
|
|
if (this_parent != parent) {
|
|
next = this_parent->d_u.d_child.next;
|
|
this_parent = this_parent->d_parent;
|
|
goto resume;
|
|
}
|
|
spin_unlock(&dcache_lock);
|
|
return 0; /* No mount points found in tree */
|
|
positive:
|
|
spin_unlock(&dcache_lock);
|
|
return 1;
|
|
}
|
|
|
|
/*
|
|
* Search the dentry child list for the specified parent,
|
|
* and move any unused dentries to the end of the unused
|
|
* list for prune_dcache(). We descend to the next level
|
|
* whenever the d_subdirs list is non-empty and continue
|
|
* searching.
|
|
*
|
|
* It returns zero iff there are no unused children,
|
|
* otherwise it returns the number of children moved to
|
|
* the end of the unused list. This may not be the total
|
|
* number of unused children, because select_parent can
|
|
* drop the lock and return early due to latency
|
|
* constraints.
|
|
*/
|
|
static int select_parent(struct dentry * parent)
|
|
{
|
|
struct dentry *this_parent = parent;
|
|
struct list_head *next;
|
|
int found = 0;
|
|
|
|
spin_lock(&dcache_lock);
|
|
repeat:
|
|
next = this_parent->d_subdirs.next;
|
|
resume:
|
|
while (next != &this_parent->d_subdirs) {
|
|
struct list_head *tmp = next;
|
|
struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child);
|
|
next = tmp->next;
|
|
|
|
dentry_lru_del_init(dentry);
|
|
/*
|
|
* move only zero ref count dentries to the end
|
|
* of the unused list for prune_dcache
|
|
*/
|
|
if (!atomic_read(&dentry->d_count)) {
|
|
dentry_lru_add_tail(dentry);
|
|
found++;
|
|
}
|
|
|
|
/*
|
|
* We can return to the caller if we have found some (this
|
|
* ensures forward progress). We'll be coming back to find
|
|
* the rest.
|
|
*/
|
|
if (found && need_resched())
|
|
goto out;
|
|
|
|
/*
|
|
* Descend a level if the d_subdirs list is non-empty.
|
|
*/
|
|
if (!list_empty(&dentry->d_subdirs)) {
|
|
this_parent = dentry;
|
|
goto repeat;
|
|
}
|
|
}
|
|
/*
|
|
* All done at this level ... ascend and resume the search.
|
|
*/
|
|
if (this_parent != parent) {
|
|
next = this_parent->d_u.d_child.next;
|
|
this_parent = this_parent->d_parent;
|
|
goto resume;
|
|
}
|
|
out:
|
|
spin_unlock(&dcache_lock);
|
|
return found;
|
|
}
|
|
|
|
/**
|
|
* shrink_dcache_parent - prune dcache
|
|
* @parent: parent of entries to prune
|
|
*
|
|
* Prune the dcache to remove unused children of the parent dentry.
|
|
*/
|
|
|
|
void shrink_dcache_parent(struct dentry * parent)
|
|
{
|
|
struct super_block *sb = parent->d_sb;
|
|
int found;
|
|
|
|
while ((found = select_parent(parent)) != 0)
|
|
__shrink_dcache_sb(sb, &found, 0);
|
|
}
|
|
|
|
/*
|
|
* Scan `nr' dentries and return the number which remain.
|
|
*
|
|
* We need to avoid reentering the filesystem if the caller is performing a
|
|
* GFP_NOFS allocation attempt. One example deadlock is:
|
|
*
|
|
* ext2_new_block->getblk->GFP->shrink_dcache_memory->prune_dcache->
|
|
* prune_one_dentry->dput->dentry_iput->iput->inode->i_sb->s_op->put_inode->
|
|
* ext2_discard_prealloc->ext2_free_blocks->lock_super->DEADLOCK.
|
|
*
|
|
* In this case we return -1 to tell the caller that we baled.
|
|
*/
|
|
static int shrink_dcache_memory(int nr, gfp_t gfp_mask)
|
|
{
|
|
if (nr) {
|
|
if (!(gfp_mask & __GFP_FS))
|
|
return -1;
|
|
prune_dcache(nr);
|
|
}
|
|
return (dentry_stat.nr_unused / 100) * sysctl_vfs_cache_pressure;
|
|
}
|
|
|
|
static struct shrinker dcache_shrinker = {
|
|
.shrink = shrink_dcache_memory,
|
|
.seeks = DEFAULT_SEEKS,
|
|
};
|
|
|
|
/**
|
|
* d_alloc - allocate a dcache entry
|
|
* @parent: parent of entry to allocate
|
|
* @name: qstr of the name
|
|
*
|
|
* Allocates a dentry. It returns %NULL if there is insufficient memory
|
|
* available. On a success the dentry is returned. The name passed in is
|
|
* copied and the copy passed in may be reused after this call.
|
|
*/
|
|
|
|
struct dentry *d_alloc(struct dentry * parent, const struct qstr *name)
|
|
{
|
|
struct dentry *dentry;
|
|
char *dname;
|
|
|
|
dentry = kmem_cache_alloc(dentry_cache, GFP_KERNEL);
|
|
if (!dentry)
|
|
return NULL;
|
|
|
|
if (name->len > DNAME_INLINE_LEN-1) {
|
|
dname = kmalloc(name->len + 1, GFP_KERNEL);
|
|
if (!dname) {
|
|
kmem_cache_free(dentry_cache, dentry);
|
|
return NULL;
|
|
}
|
|
} else {
|
|
dname = dentry->d_iname;
|
|
}
|
|
dentry->d_name.name = dname;
|
|
|
|
dentry->d_name.len = name->len;
|
|
dentry->d_name.hash = name->hash;
|
|
memcpy(dname, name->name, name->len);
|
|
dname[name->len] = 0;
|
|
|
|
atomic_set(&dentry->d_count, 1);
|
|
dentry->d_flags = DCACHE_UNHASHED;
|
|
spin_lock_init(&dentry->d_lock);
|
|
dentry->d_inode = NULL;
|
|
dentry->d_parent = NULL;
|
|
dentry->d_sb = NULL;
|
|
dentry->d_op = NULL;
|
|
dentry->d_fsdata = NULL;
|
|
dentry->d_mounted = 0;
|
|
INIT_HLIST_NODE(&dentry->d_hash);
|
|
INIT_LIST_HEAD(&dentry->d_lru);
|
|
INIT_LIST_HEAD(&dentry->d_subdirs);
|
|
INIT_LIST_HEAD(&dentry->d_alias);
|
|
|
|
if (parent) {
|
|
dentry->d_parent = dget(parent);
|
|
dentry->d_sb = parent->d_sb;
|
|
} else {
|
|
INIT_LIST_HEAD(&dentry->d_u.d_child);
|
|
}
|
|
|
|
spin_lock(&dcache_lock);
|
|
if (parent)
|
|
list_add(&dentry->d_u.d_child, &parent->d_subdirs);
|
|
dentry_stat.nr_dentry++;
|
|
spin_unlock(&dcache_lock);
|
|
|
|
return dentry;
|
|
}
|
|
|
|
struct dentry *d_alloc_name(struct dentry *parent, const char *name)
|
|
{
|
|
struct qstr q;
|
|
|
|
q.name = name;
|
|
q.len = strlen(name);
|
|
q.hash = full_name_hash(q.name, q.len);
|
|
return d_alloc(parent, &q);
|
|
}
|
|
|
|
/* the caller must hold dcache_lock */
|
|
static void __d_instantiate(struct dentry *dentry, struct inode *inode)
|
|
{
|
|
if (inode)
|
|
list_add(&dentry->d_alias, &inode->i_dentry);
|
|
dentry->d_inode = inode;
|
|
fsnotify_d_instantiate(dentry, inode);
|
|
}
|
|
|
|
/**
|
|
* d_instantiate - fill in inode information for a dentry
|
|
* @entry: dentry to complete
|
|
* @inode: inode to attach to this dentry
|
|
*
|
|
* Fill in inode information in the entry.
|
|
*
|
|
* This turns negative dentries into productive full members
|
|
* of society.
|
|
*
|
|
* NOTE! This assumes that the inode count has been incremented
|
|
* (or otherwise set) by the caller to indicate that it is now
|
|
* in use by the dcache.
|
|
*/
|
|
|
|
void d_instantiate(struct dentry *entry, struct inode * inode)
|
|
{
|
|
BUG_ON(!list_empty(&entry->d_alias));
|
|
spin_lock(&dcache_lock);
|
|
__d_instantiate(entry, inode);
|
|
spin_unlock(&dcache_lock);
|
|
security_d_instantiate(entry, inode);
|
|
}
|
|
|
|
/**
|
|
* d_instantiate_unique - instantiate a non-aliased dentry
|
|
* @entry: dentry to instantiate
|
|
* @inode: inode to attach to this dentry
|
|
*
|
|
* Fill in inode information in the entry. On success, it returns NULL.
|
|
* If an unhashed alias of "entry" already exists, then we return the
|
|
* aliased dentry instead and drop one reference to inode.
|
|
*
|
|
* Note that in order to avoid conflicts with rename() etc, the caller
|
|
* had better be holding the parent directory semaphore.
|
|
*
|
|
* This also assumes that the inode count has been incremented
|
|
* (or otherwise set) by the caller to indicate that it is now
|
|
* in use by the dcache.
|
|
*/
|
|
static struct dentry *__d_instantiate_unique(struct dentry *entry,
|
|
struct inode *inode)
|
|
{
|
|
struct dentry *alias;
|
|
int len = entry->d_name.len;
|
|
const char *name = entry->d_name.name;
|
|
unsigned int hash = entry->d_name.hash;
|
|
|
|
if (!inode) {
|
|
__d_instantiate(entry, NULL);
|
|
return NULL;
|
|
}
|
|
|
|
list_for_each_entry(alias, &inode->i_dentry, d_alias) {
|
|
struct qstr *qstr = &alias->d_name;
|
|
|
|
if (qstr->hash != hash)
|
|
continue;
|
|
if (alias->d_parent != entry->d_parent)
|
|
continue;
|
|
if (qstr->len != len)
|
|
continue;
|
|
if (memcmp(qstr->name, name, len))
|
|
continue;
|
|
dget_locked(alias);
|
|
return alias;
|
|
}
|
|
|
|
__d_instantiate(entry, inode);
|
|
return NULL;
|
|
}
|
|
|
|
struct dentry *d_instantiate_unique(struct dentry *entry, struct inode *inode)
|
|
{
|
|
struct dentry *result;
|
|
|
|
BUG_ON(!list_empty(&entry->d_alias));
|
|
|
|
spin_lock(&dcache_lock);
|
|
result = __d_instantiate_unique(entry, inode);
|
|
spin_unlock(&dcache_lock);
|
|
|
|
if (!result) {
|
|
security_d_instantiate(entry, inode);
|
|
return NULL;
|
|
}
|
|
|
|
BUG_ON(!d_unhashed(result));
|
|
iput(inode);
|
|
return result;
|
|
}
|
|
|
|
EXPORT_SYMBOL(d_instantiate_unique);
|
|
|
|
/**
|
|
* d_alloc_root - allocate root dentry
|
|
* @root_inode: inode to allocate the root for
|
|
*
|
|
* Allocate a root ("/") dentry for the inode given. The inode is
|
|
* instantiated and returned. %NULL is returned if there is insufficient
|
|
* memory or the inode passed is %NULL.
|
|
*/
|
|
|
|
struct dentry * d_alloc_root(struct inode * root_inode)
|
|
{
|
|
struct dentry *res = NULL;
|
|
|
|
if (root_inode) {
|
|
static const struct qstr name = { .name = "/", .len = 1 };
|
|
|
|
res = d_alloc(NULL, &name);
|
|
if (res) {
|
|
res->d_sb = root_inode->i_sb;
|
|
res->d_parent = res;
|
|
d_instantiate(res, root_inode);
|
|
}
|
|
}
|
|
return res;
|
|
}
|
|
|
|
static inline struct hlist_head *d_hash(struct dentry *parent,
|
|
unsigned long hash)
|
|
{
|
|
hash += ((unsigned long) parent ^ GOLDEN_RATIO_PRIME) / L1_CACHE_BYTES;
|
|
hash = hash ^ ((hash ^ GOLDEN_RATIO_PRIME) >> D_HASHBITS);
|
|
return dentry_hashtable + (hash & D_HASHMASK);
|
|
}
|
|
|
|
/**
|
|
* d_obtain_alias - find or allocate a dentry for a given inode
|
|
* @inode: inode to allocate the dentry for
|
|
*
|
|
* Obtain a dentry for an inode resulting from NFS filehandle conversion or
|
|
* similar open by handle operations. The returned dentry may be anonymous,
|
|
* or may have a full name (if the inode was already in the cache).
|
|
*
|
|
* When called on a directory inode, we must ensure that the inode only ever
|
|
* has one dentry. If a dentry is found, that is returned instead of
|
|
* allocating a new one.
|
|
*
|
|
* On successful return, the reference to the inode has been transferred
|
|
* to the dentry. In case of an error the reference on the inode is released.
|
|
* To make it easier to use in export operations a %NULL or IS_ERR inode may
|
|
* be passed in and will be the error will be propagate to the return value,
|
|
* with a %NULL @inode replaced by ERR_PTR(-ESTALE).
|
|
*/
|
|
struct dentry *d_obtain_alias(struct inode *inode)
|
|
{
|
|
static const struct qstr anonstring = { .name = "" };
|
|
struct dentry *tmp;
|
|
struct dentry *res;
|
|
|
|
if (!inode)
|
|
return ERR_PTR(-ESTALE);
|
|
if (IS_ERR(inode))
|
|
return ERR_CAST(inode);
|
|
|
|
res = d_find_alias(inode);
|
|
if (res)
|
|
goto out_iput;
|
|
|
|
tmp = d_alloc(NULL, &anonstring);
|
|
if (!tmp) {
|
|
res = ERR_PTR(-ENOMEM);
|
|
goto out_iput;
|
|
}
|
|
tmp->d_parent = tmp; /* make sure dput doesn't croak */
|
|
|
|
spin_lock(&dcache_lock);
|
|
res = __d_find_alias(inode, 0);
|
|
if (res) {
|
|
spin_unlock(&dcache_lock);
|
|
dput(tmp);
|
|
goto out_iput;
|
|
}
|
|
|
|
/* attach a disconnected dentry */
|
|
spin_lock(&tmp->d_lock);
|
|
tmp->d_sb = inode->i_sb;
|
|
tmp->d_inode = inode;
|
|
tmp->d_flags |= DCACHE_DISCONNECTED;
|
|
tmp->d_flags &= ~DCACHE_UNHASHED;
|
|
list_add(&tmp->d_alias, &inode->i_dentry);
|
|
hlist_add_head(&tmp->d_hash, &inode->i_sb->s_anon);
|
|
spin_unlock(&tmp->d_lock);
|
|
|
|
spin_unlock(&dcache_lock);
|
|
return tmp;
|
|
|
|
out_iput:
|
|
iput(inode);
|
|
return res;
|
|
}
|
|
EXPORT_SYMBOL(d_obtain_alias);
|
|
|
|
/**
|
|
* d_splice_alias - splice a disconnected dentry into the tree if one exists
|
|
* @inode: the inode which may have a disconnected dentry
|
|
* @dentry: a negative dentry which we want to point to the inode.
|
|
*
|
|
* If inode is a directory and has a 'disconnected' dentry (i.e. IS_ROOT and
|
|
* DCACHE_DISCONNECTED), then d_move that in place of the given dentry
|
|
* and return it, else simply d_add the inode to the dentry and return NULL.
|
|
*
|
|
* This is needed in the lookup routine of any filesystem that is exportable
|
|
* (via knfsd) so that we can build dcache paths to directories effectively.
|
|
*
|
|
* If a dentry was found and moved, then it is returned. Otherwise NULL
|
|
* is returned. This matches the expected return value of ->lookup.
|
|
*
|
|
*/
|
|
struct dentry *d_splice_alias(struct inode *inode, struct dentry *dentry)
|
|
{
|
|
struct dentry *new = NULL;
|
|
|
|
if (inode && S_ISDIR(inode->i_mode)) {
|
|
spin_lock(&dcache_lock);
|
|
new = __d_find_alias(inode, 1);
|
|
if (new) {
|
|
BUG_ON(!(new->d_flags & DCACHE_DISCONNECTED));
|
|
spin_unlock(&dcache_lock);
|
|
security_d_instantiate(new, inode);
|
|
d_rehash(dentry);
|
|
d_move(new, dentry);
|
|
iput(inode);
|
|
} else {
|
|
/* already taking dcache_lock, so d_add() by hand */
|
|
__d_instantiate(dentry, inode);
|
|
spin_unlock(&dcache_lock);
|
|
security_d_instantiate(dentry, inode);
|
|
d_rehash(dentry);
|
|
}
|
|
} else
|
|
d_add(dentry, inode);
|
|
return new;
|
|
}
|
|
|
|
/**
|
|
* d_add_ci - lookup or allocate new dentry with case-exact name
|
|
* @inode: the inode case-insensitive lookup has found
|
|
* @dentry: the negative dentry that was passed to the parent's lookup func
|
|
* @name: the case-exact name to be associated with the returned dentry
|
|
*
|
|
* This is to avoid filling the dcache with case-insensitive names to the
|
|
* same inode, only the actual correct case is stored in the dcache for
|
|
* case-insensitive filesystems.
|
|
*
|
|
* For a case-insensitive lookup match and if the the case-exact dentry
|
|
* already exists in in the dcache, use it and return it.
|
|
*
|
|
* If no entry exists with the exact case name, allocate new dentry with
|
|
* the exact case, and return the spliced entry.
|
|
*/
|
|
struct dentry *d_add_ci(struct dentry *dentry, struct inode *inode,
|
|
struct qstr *name)
|
|
{
|
|
int error;
|
|
struct dentry *found;
|
|
struct dentry *new;
|
|
|
|
/*
|
|
* First check if a dentry matching the name already exists,
|
|
* if not go ahead and create it now.
|
|
*/
|
|
found = d_hash_and_lookup(dentry->d_parent, name);
|
|
if (!found) {
|
|
new = d_alloc(dentry->d_parent, name);
|
|
if (!new) {
|
|
error = -ENOMEM;
|
|
goto err_out;
|
|
}
|
|
|
|
found = d_splice_alias(inode, new);
|
|
if (found) {
|
|
dput(new);
|
|
return found;
|
|
}
|
|
return new;
|
|
}
|
|
|
|
/*
|
|
* If a matching dentry exists, and it's not negative use it.
|
|
*
|
|
* Decrement the reference count to balance the iget() done
|
|
* earlier on.
|
|
*/
|
|
if (found->d_inode) {
|
|
if (unlikely(found->d_inode != inode)) {
|
|
/* This can't happen because bad inodes are unhashed. */
|
|
BUG_ON(!is_bad_inode(inode));
|
|
BUG_ON(!is_bad_inode(found->d_inode));
|
|
}
|
|
iput(inode);
|
|
return found;
|
|
}
|
|
|
|
/*
|
|
* Negative dentry: instantiate it unless the inode is a directory and
|
|
* already has a dentry.
|
|
*/
|
|
spin_lock(&dcache_lock);
|
|
if (!S_ISDIR(inode->i_mode) || list_empty(&inode->i_dentry)) {
|
|
__d_instantiate(found, inode);
|
|
spin_unlock(&dcache_lock);
|
|
security_d_instantiate(found, inode);
|
|
return found;
|
|
}
|
|
|
|
/*
|
|
* In case a directory already has a (disconnected) entry grab a
|
|
* reference to it, move it in place and use it.
|
|
*/
|
|
new = list_entry(inode->i_dentry.next, struct dentry, d_alias);
|
|
dget_locked(new);
|
|
spin_unlock(&dcache_lock);
|
|
security_d_instantiate(found, inode);
|
|
d_move(new, found);
|
|
iput(inode);
|
|
dput(found);
|
|
return new;
|
|
|
|
err_out:
|
|
iput(inode);
|
|
return ERR_PTR(error);
|
|
}
|
|
|
|
/**
|
|
* d_lookup - search for a dentry
|
|
* @parent: parent dentry
|
|
* @name: qstr of name we wish to find
|
|
*
|
|
* Searches the children of the parent dentry for the name in question. If
|
|
* the dentry is found its reference count is incremented and the dentry
|
|
* is returned. The caller must use dput to free the entry when it has
|
|
* finished using it. %NULL is returned on failure.
|
|
*
|
|
* __d_lookup is dcache_lock free. The hash list is protected using RCU.
|
|
* Memory barriers are used while updating and doing lockless traversal.
|
|
* To avoid races with d_move while rename is happening, d_lock is used.
|
|
*
|
|
* Overflows in memcmp(), while d_move, are avoided by keeping the length
|
|
* and name pointer in one structure pointed by d_qstr.
|
|
*
|
|
* rcu_read_lock() and rcu_read_unlock() are used to disable preemption while
|
|
* lookup is going on.
|
|
*
|
|
* The dentry unused LRU is not updated even if lookup finds the required dentry
|
|
* in there. It is updated in places such as prune_dcache, shrink_dcache_sb,
|
|
* select_parent and __dget_locked. This laziness saves lookup from dcache_lock
|
|
* acquisition.
|
|
*
|
|
* d_lookup() is protected against the concurrent renames in some unrelated
|
|
* directory using the seqlockt_t rename_lock.
|
|
*/
|
|
|
|
struct dentry * d_lookup(struct dentry * parent, struct qstr * name)
|
|
{
|
|
struct dentry * dentry = NULL;
|
|
unsigned long seq;
|
|
|
|
do {
|
|
seq = read_seqbegin(&rename_lock);
|
|
dentry = __d_lookup(parent, name);
|
|
if (dentry)
|
|
break;
|
|
} while (read_seqretry(&rename_lock, seq));
|
|
return dentry;
|
|
}
|
|
|
|
struct dentry * __d_lookup(struct dentry * parent, struct qstr * name)
|
|
{
|
|
unsigned int len = name->len;
|
|
unsigned int hash = name->hash;
|
|
const unsigned char *str = name->name;
|
|
struct hlist_head *head = d_hash(parent,hash);
|
|
struct dentry *found = NULL;
|
|
struct hlist_node *node;
|
|
struct dentry *dentry;
|
|
|
|
rcu_read_lock();
|
|
|
|
hlist_for_each_entry_rcu(dentry, node, head, d_hash) {
|
|
struct qstr *qstr;
|
|
|
|
if (dentry->d_name.hash != hash)
|
|
continue;
|
|
if (dentry->d_parent != parent)
|
|
continue;
|
|
|
|
spin_lock(&dentry->d_lock);
|
|
|
|
/*
|
|
* Recheck the dentry after taking the lock - d_move may have
|
|
* changed things. Don't bother checking the hash because we're
|
|
* about to compare the whole name anyway.
|
|
*/
|
|
if (dentry->d_parent != parent)
|
|
goto next;
|
|
|
|
/* non-existing due to RCU? */
|
|
if (d_unhashed(dentry))
|
|
goto next;
|
|
|
|
/*
|
|
* It is safe to compare names since d_move() cannot
|
|
* change the qstr (protected by d_lock).
|
|
*/
|
|
qstr = &dentry->d_name;
|
|
if (parent->d_op && parent->d_op->d_compare) {
|
|
if (parent->d_op->d_compare(parent, qstr, name))
|
|
goto next;
|
|
} else {
|
|
if (qstr->len != len)
|
|
goto next;
|
|
if (memcmp(qstr->name, str, len))
|
|
goto next;
|
|
}
|
|
|
|
atomic_inc(&dentry->d_count);
|
|
found = dentry;
|
|
spin_unlock(&dentry->d_lock);
|
|
break;
|
|
next:
|
|
spin_unlock(&dentry->d_lock);
|
|
}
|
|
rcu_read_unlock();
|
|
|
|
return found;
|
|
}
|
|
|
|
/**
|
|
* d_hash_and_lookup - hash the qstr then search for a dentry
|
|
* @dir: Directory to search in
|
|
* @name: qstr of name we wish to find
|
|
*
|
|
* On hash failure or on lookup failure NULL is returned.
|
|
*/
|
|
struct dentry *d_hash_and_lookup(struct dentry *dir, struct qstr *name)
|
|
{
|
|
struct dentry *dentry = NULL;
|
|
|
|
/*
|
|
* Check for a fs-specific hash function. Note that we must
|
|
* calculate the standard hash first, as the d_op->d_hash()
|
|
* routine may choose to leave the hash value unchanged.
|
|
*/
|
|
name->hash = full_name_hash(name->name, name->len);
|
|
if (dir->d_op && dir->d_op->d_hash) {
|
|
if (dir->d_op->d_hash(dir, name) < 0)
|
|
goto out;
|
|
}
|
|
dentry = d_lookup(dir, name);
|
|
out:
|
|
return dentry;
|
|
}
|
|
|
|
/**
|
|
* d_validate - verify dentry provided from insecure source
|
|
* @dentry: The dentry alleged to be valid child of @dparent
|
|
* @dparent: The parent dentry (known to be valid)
|
|
*
|
|
* An insecure source has sent us a dentry, here we verify it and dget() it.
|
|
* This is used by ncpfs in its readdir implementation.
|
|
* Zero is returned in the dentry is invalid.
|
|
*/
|
|
|
|
int d_validate(struct dentry *dentry, struct dentry *dparent)
|
|
{
|
|
struct hlist_head *base;
|
|
struct hlist_node *lhp;
|
|
|
|
/* Check whether the ptr might be valid at all.. */
|
|
if (!kmem_ptr_validate(dentry_cache, dentry))
|
|
goto out;
|
|
|
|
if (dentry->d_parent != dparent)
|
|
goto out;
|
|
|
|
spin_lock(&dcache_lock);
|
|
base = d_hash(dparent, dentry->d_name.hash);
|
|
hlist_for_each(lhp,base) {
|
|
/* hlist_for_each_entry_rcu() not required for d_hash list
|
|
* as it is parsed under dcache_lock
|
|
*/
|
|
if (dentry == hlist_entry(lhp, struct dentry, d_hash)) {
|
|
__dget_locked(dentry);
|
|
spin_unlock(&dcache_lock);
|
|
return 1;
|
|
}
|
|
}
|
|
spin_unlock(&dcache_lock);
|
|
out:
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* When a file is deleted, we have two options:
|
|
* - turn this dentry into a negative dentry
|
|
* - unhash this dentry and free it.
|
|
*
|
|
* Usually, we want to just turn this into
|
|
* a negative dentry, but if anybody else is
|
|
* currently using the dentry or the inode
|
|
* we can't do that and we fall back on removing
|
|
* it from the hash queues and waiting for
|
|
* it to be deleted later when it has no users
|
|
*/
|
|
|
|
/**
|
|
* d_delete - delete a dentry
|
|
* @dentry: The dentry to delete
|
|
*
|
|
* Turn the dentry into a negative dentry if possible, otherwise
|
|
* remove it from the hash queues so it can be deleted later
|
|
*/
|
|
|
|
void d_delete(struct dentry * dentry)
|
|
{
|
|
int isdir = 0;
|
|
/*
|
|
* Are we the only user?
|
|
*/
|
|
spin_lock(&dcache_lock);
|
|
spin_lock(&dentry->d_lock);
|
|
isdir = S_ISDIR(dentry->d_inode->i_mode);
|
|
if (atomic_read(&dentry->d_count) == 1) {
|
|
dentry_iput(dentry);
|
|
fsnotify_nameremove(dentry, isdir);
|
|
return;
|
|
}
|
|
|
|
if (!d_unhashed(dentry))
|
|
__d_drop(dentry);
|
|
|
|
spin_unlock(&dentry->d_lock);
|
|
spin_unlock(&dcache_lock);
|
|
|
|
fsnotify_nameremove(dentry, isdir);
|
|
}
|
|
|
|
static void __d_rehash(struct dentry * entry, struct hlist_head *list)
|
|
{
|
|
|
|
entry->d_flags &= ~DCACHE_UNHASHED;
|
|
hlist_add_head_rcu(&entry->d_hash, list);
|
|
}
|
|
|
|
static void _d_rehash(struct dentry * entry)
|
|
{
|
|
__d_rehash(entry, d_hash(entry->d_parent, entry->d_name.hash));
|
|
}
|
|
|
|
/**
|
|
* d_rehash - add an entry back to the hash
|
|
* @entry: dentry to add to the hash
|
|
*
|
|
* Adds a dentry to the hash according to its name.
|
|
*/
|
|
|
|
void d_rehash(struct dentry * entry)
|
|
{
|
|
spin_lock(&dcache_lock);
|
|
spin_lock(&entry->d_lock);
|
|
_d_rehash(entry);
|
|
spin_unlock(&entry->d_lock);
|
|
spin_unlock(&dcache_lock);
|
|
}
|
|
|
|
/*
|
|
* When switching names, the actual string doesn't strictly have to
|
|
* be preserved in the target - because we're dropping the target
|
|
* anyway. As such, we can just do a simple memcpy() to copy over
|
|
* the new name before we switch.
|
|
*
|
|
* Note that we have to be a lot more careful about getting the hash
|
|
* switched - we have to switch the hash value properly even if it
|
|
* then no longer matches the actual (corrupted) string of the target.
|
|
* The hash value has to match the hash queue that the dentry is on..
|
|
*/
|
|
static void switch_names(struct dentry *dentry, struct dentry *target)
|
|
{
|
|
if (dname_external(target)) {
|
|
if (dname_external(dentry)) {
|
|
/*
|
|
* Both external: swap the pointers
|
|
*/
|
|
swap(target->d_name.name, dentry->d_name.name);
|
|
} else {
|
|
/*
|
|
* dentry:internal, target:external. Steal target's
|
|
* storage and make target internal.
|
|
*/
|
|
memcpy(target->d_iname, dentry->d_name.name,
|
|
dentry->d_name.len + 1);
|
|
dentry->d_name.name = target->d_name.name;
|
|
target->d_name.name = target->d_iname;
|
|
}
|
|
} else {
|
|
if (dname_external(dentry)) {
|
|
/*
|
|
* dentry:external, target:internal. Give dentry's
|
|
* storage to target and make dentry internal
|
|
*/
|
|
memcpy(dentry->d_iname, target->d_name.name,
|
|
target->d_name.len + 1);
|
|
target->d_name.name = dentry->d_name.name;
|
|
dentry->d_name.name = dentry->d_iname;
|
|
} else {
|
|
/*
|
|
* Both are internal. Just copy target to dentry
|
|
*/
|
|
memcpy(dentry->d_iname, target->d_name.name,
|
|
target->d_name.len + 1);
|
|
dentry->d_name.len = target->d_name.len;
|
|
return;
|
|
}
|
|
}
|
|
swap(dentry->d_name.len, target->d_name.len);
|
|
}
|
|
|
|
/*
|
|
* We cannibalize "target" when moving dentry on top of it,
|
|
* because it's going to be thrown away anyway. We could be more
|
|
* polite about it, though.
|
|
*
|
|
* This forceful removal will result in ugly /proc output if
|
|
* somebody holds a file open that got deleted due to a rename.
|
|
* We could be nicer about the deleted file, and let it show
|
|
* up under the name it had before it was deleted rather than
|
|
* under the original name of the file that was moved on top of it.
|
|
*/
|
|
|
|
/*
|
|
* d_move_locked - move a dentry
|
|
* @dentry: entry to move
|
|
* @target: new dentry
|
|
*
|
|
* Update the dcache to reflect the move of a file name. Negative
|
|
* dcache entries should not be moved in this way.
|
|
*/
|
|
static void d_move_locked(struct dentry * dentry, struct dentry * target)
|
|
{
|
|
struct hlist_head *list;
|
|
|
|
if (!dentry->d_inode)
|
|
printk(KERN_WARNING "VFS: moving negative dcache entry\n");
|
|
|
|
write_seqlock(&rename_lock);
|
|
/*
|
|
* XXXX: do we really need to take target->d_lock?
|
|
*/
|
|
if (target < dentry) {
|
|
spin_lock(&target->d_lock);
|
|
spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
|
|
} else {
|
|
spin_lock(&dentry->d_lock);
|
|
spin_lock_nested(&target->d_lock, DENTRY_D_LOCK_NESTED);
|
|
}
|
|
|
|
/* Move the dentry to the target hash queue, if on different bucket */
|
|
if (d_unhashed(dentry))
|
|
goto already_unhashed;
|
|
|
|
hlist_del_rcu(&dentry->d_hash);
|
|
|
|
already_unhashed:
|
|
list = d_hash(target->d_parent, target->d_name.hash);
|
|
__d_rehash(dentry, list);
|
|
|
|
/* Unhash the target: dput() will then get rid of it */
|
|
__d_drop(target);
|
|
|
|
list_del(&dentry->d_u.d_child);
|
|
list_del(&target->d_u.d_child);
|
|
|
|
/* Switch the names.. */
|
|
switch_names(dentry, target);
|
|
swap(dentry->d_name.hash, target->d_name.hash);
|
|
|
|
/* ... and switch the parents */
|
|
if (IS_ROOT(dentry)) {
|
|
dentry->d_parent = target->d_parent;
|
|
target->d_parent = target;
|
|
INIT_LIST_HEAD(&target->d_u.d_child);
|
|
} else {
|
|
swap(dentry->d_parent, target->d_parent);
|
|
|
|
/* And add them back to the (new) parent lists */
|
|
list_add(&target->d_u.d_child, &target->d_parent->d_subdirs);
|
|
}
|
|
|
|
list_add(&dentry->d_u.d_child, &dentry->d_parent->d_subdirs);
|
|
spin_unlock(&target->d_lock);
|
|
fsnotify_d_move(dentry);
|
|
spin_unlock(&dentry->d_lock);
|
|
write_sequnlock(&rename_lock);
|
|
}
|
|
|
|
/**
|
|
* d_move - move a dentry
|
|
* @dentry: entry to move
|
|
* @target: new dentry
|
|
*
|
|
* Update the dcache to reflect the move of a file name. Negative
|
|
* dcache entries should not be moved in this way.
|
|
*/
|
|
|
|
void d_move(struct dentry * dentry, struct dentry * target)
|
|
{
|
|
spin_lock(&dcache_lock);
|
|
d_move_locked(dentry, target);
|
|
spin_unlock(&dcache_lock);
|
|
}
|
|
|
|
/**
|
|
* d_ancestor - search for an ancestor
|
|
* @p1: ancestor dentry
|
|
* @p2: child dentry
|
|
*
|
|
* Returns the ancestor dentry of p2 which is a child of p1, if p1 is
|
|
* an ancestor of p2, else NULL.
|
|
*/
|
|
struct dentry *d_ancestor(struct dentry *p1, struct dentry *p2)
|
|
{
|
|
struct dentry *p;
|
|
|
|
for (p = p2; !IS_ROOT(p); p = p->d_parent) {
|
|
if (p->d_parent == p1)
|
|
return p;
|
|
}
|
|
return NULL;
|
|
}
|
|
|
|
/*
|
|
* This helper attempts to cope with remotely renamed directories
|
|
*
|
|
* It assumes that the caller is already holding
|
|
* dentry->d_parent->d_inode->i_mutex and the dcache_lock
|
|
*
|
|
* Note: If ever the locking in lock_rename() changes, then please
|
|
* remember to update this too...
|
|
*/
|
|
static struct dentry *__d_unalias(struct dentry *dentry, struct dentry *alias)
|
|
__releases(dcache_lock)
|
|
{
|
|
struct mutex *m1 = NULL, *m2 = NULL;
|
|
struct dentry *ret;
|
|
|
|
/* If alias and dentry share a parent, then no extra locks required */
|
|
if (alias->d_parent == dentry->d_parent)
|
|
goto out_unalias;
|
|
|
|
/* Check for loops */
|
|
ret = ERR_PTR(-ELOOP);
|
|
if (d_ancestor(alias, dentry))
|
|
goto out_err;
|
|
|
|
/* See lock_rename() */
|
|
ret = ERR_PTR(-EBUSY);
|
|
if (!mutex_trylock(&dentry->d_sb->s_vfs_rename_mutex))
|
|
goto out_err;
|
|
m1 = &dentry->d_sb->s_vfs_rename_mutex;
|
|
if (!mutex_trylock(&alias->d_parent->d_inode->i_mutex))
|
|
goto out_err;
|
|
m2 = &alias->d_parent->d_inode->i_mutex;
|
|
out_unalias:
|
|
d_move_locked(alias, dentry);
|
|
ret = alias;
|
|
out_err:
|
|
spin_unlock(&dcache_lock);
|
|
if (m2)
|
|
mutex_unlock(m2);
|
|
if (m1)
|
|
mutex_unlock(m1);
|
|
return ret;
|
|
}
|
|
|
|
/*
|
|
* Prepare an anonymous dentry for life in the superblock's dentry tree as a
|
|
* named dentry in place of the dentry to be replaced.
|
|
*/
|
|
static void __d_materialise_dentry(struct dentry *dentry, struct dentry *anon)
|
|
{
|
|
struct dentry *dparent, *aparent;
|
|
|
|
switch_names(dentry, anon);
|
|
swap(dentry->d_name.hash, anon->d_name.hash);
|
|
|
|
dparent = dentry->d_parent;
|
|
aparent = anon->d_parent;
|
|
|
|
dentry->d_parent = (aparent == anon) ? dentry : aparent;
|
|
list_del(&dentry->d_u.d_child);
|
|
if (!IS_ROOT(dentry))
|
|
list_add(&dentry->d_u.d_child, &dentry->d_parent->d_subdirs);
|
|
else
|
|
INIT_LIST_HEAD(&dentry->d_u.d_child);
|
|
|
|
anon->d_parent = (dparent == dentry) ? anon : dparent;
|
|
list_del(&anon->d_u.d_child);
|
|
if (!IS_ROOT(anon))
|
|
list_add(&anon->d_u.d_child, &anon->d_parent->d_subdirs);
|
|
else
|
|
INIT_LIST_HEAD(&anon->d_u.d_child);
|
|
|
|
anon->d_flags &= ~DCACHE_DISCONNECTED;
|
|
}
|
|
|
|
/**
|
|
* d_materialise_unique - introduce an inode into the tree
|
|
* @dentry: candidate dentry
|
|
* @inode: inode to bind to the dentry, to which aliases may be attached
|
|
*
|
|
* Introduces an dentry into the tree, substituting an extant disconnected
|
|
* root directory alias in its place if there is one
|
|
*/
|
|
struct dentry *d_materialise_unique(struct dentry *dentry, struct inode *inode)
|
|
{
|
|
struct dentry *actual;
|
|
|
|
BUG_ON(!d_unhashed(dentry));
|
|
|
|
spin_lock(&dcache_lock);
|
|
|
|
if (!inode) {
|
|
actual = dentry;
|
|
__d_instantiate(dentry, NULL);
|
|
goto found_lock;
|
|
}
|
|
|
|
if (S_ISDIR(inode->i_mode)) {
|
|
struct dentry *alias;
|
|
|
|
/* Does an aliased dentry already exist? */
|
|
alias = __d_find_alias(inode, 0);
|
|
if (alias) {
|
|
actual = alias;
|
|
/* Is this an anonymous mountpoint that we could splice
|
|
* into our tree? */
|
|
if (IS_ROOT(alias)) {
|
|
spin_lock(&alias->d_lock);
|
|
__d_materialise_dentry(dentry, alias);
|
|
__d_drop(alias);
|
|
goto found;
|
|
}
|
|
/* Nope, but we must(!) avoid directory aliasing */
|
|
actual = __d_unalias(dentry, alias);
|
|
if (IS_ERR(actual))
|
|
dput(alias);
|
|
goto out_nolock;
|
|
}
|
|
}
|
|
|
|
/* Add a unique reference */
|
|
actual = __d_instantiate_unique(dentry, inode);
|
|
if (!actual)
|
|
actual = dentry;
|
|
else if (unlikely(!d_unhashed(actual)))
|
|
goto shouldnt_be_hashed;
|
|
|
|
found_lock:
|
|
spin_lock(&actual->d_lock);
|
|
found:
|
|
_d_rehash(actual);
|
|
spin_unlock(&actual->d_lock);
|
|
spin_unlock(&dcache_lock);
|
|
out_nolock:
|
|
if (actual == dentry) {
|
|
security_d_instantiate(dentry, inode);
|
|
return NULL;
|
|
}
|
|
|
|
iput(inode);
|
|
return actual;
|
|
|
|
shouldnt_be_hashed:
|
|
spin_unlock(&dcache_lock);
|
|
BUG();
|
|
}
|
|
|
|
static int prepend(char **buffer, int *buflen, const char *str, int namelen)
|
|
{
|
|
*buflen -= namelen;
|
|
if (*buflen < 0)
|
|
return -ENAMETOOLONG;
|
|
*buffer -= namelen;
|
|
memcpy(*buffer, str, namelen);
|
|
return 0;
|
|
}
|
|
|
|
static int prepend_name(char **buffer, int *buflen, struct qstr *name)
|
|
{
|
|
return prepend(buffer, buflen, name->name, name->len);
|
|
}
|
|
|
|
/**
|
|
* __d_path - return the path of a dentry
|
|
* @path: the dentry/vfsmount to report
|
|
* @root: root vfsmnt/dentry (may be modified by this function)
|
|
* @buffer: buffer to return value in
|
|
* @buflen: buffer length
|
|
*
|
|
* Convert a dentry into an ASCII path name. If the entry has been deleted
|
|
* the string " (deleted)" is appended. Note that this is ambiguous.
|
|
*
|
|
* Returns a pointer into the buffer or an error code if the
|
|
* path was too long.
|
|
*
|
|
* "buflen" should be positive. Caller holds the dcache_lock.
|
|
*
|
|
* If path is not reachable from the supplied root, then the value of
|
|
* root is changed (without modifying refcounts).
|
|
*/
|
|
char *__d_path(const struct path *path, struct path *root,
|
|
char *buffer, int buflen)
|
|
{
|
|
struct dentry *dentry = path->dentry;
|
|
struct vfsmount *vfsmnt = path->mnt;
|
|
char *end = buffer + buflen;
|
|
char *retval;
|
|
|
|
spin_lock(&vfsmount_lock);
|
|
prepend(&end, &buflen, "\0", 1);
|
|
if (!IS_ROOT(dentry) && d_unhashed(dentry) &&
|
|
(prepend(&end, &buflen, " (deleted)", 10) != 0))
|
|
goto Elong;
|
|
|
|
if (buflen < 1)
|
|
goto Elong;
|
|
/* Get '/' right */
|
|
retval = end-1;
|
|
*retval = '/';
|
|
|
|
for (;;) {
|
|
struct dentry * parent;
|
|
|
|
if (dentry == root->dentry && vfsmnt == root->mnt)
|
|
break;
|
|
if (dentry == vfsmnt->mnt_root || IS_ROOT(dentry)) {
|
|
/* Global root? */
|
|
if (vfsmnt->mnt_parent == vfsmnt) {
|
|
goto global_root;
|
|
}
|
|
dentry = vfsmnt->mnt_mountpoint;
|
|
vfsmnt = vfsmnt->mnt_parent;
|
|
continue;
|
|
}
|
|
parent = dentry->d_parent;
|
|
prefetch(parent);
|
|
if ((prepend_name(&end, &buflen, &dentry->d_name) != 0) ||
|
|
(prepend(&end, &buflen, "/", 1) != 0))
|
|
goto Elong;
|
|
retval = end;
|
|
dentry = parent;
|
|
}
|
|
|
|
out:
|
|
spin_unlock(&vfsmount_lock);
|
|
return retval;
|
|
|
|
global_root:
|
|
retval += 1; /* hit the slash */
|
|
if (prepend_name(&retval, &buflen, &dentry->d_name) != 0)
|
|
goto Elong;
|
|
root->mnt = vfsmnt;
|
|
root->dentry = dentry;
|
|
goto out;
|
|
|
|
Elong:
|
|
retval = ERR_PTR(-ENAMETOOLONG);
|
|
goto out;
|
|
}
|
|
|
|
/**
|
|
* d_path - return the path of a dentry
|
|
* @path: path to report
|
|
* @buf: buffer to return value in
|
|
* @buflen: buffer length
|
|
*
|
|
* Convert a dentry into an ASCII path name. If the entry has been deleted
|
|
* the string " (deleted)" is appended. Note that this is ambiguous.
|
|
*
|
|
* Returns a pointer into the buffer or an error code if the path was
|
|
* too long. Note: Callers should use the returned pointer, not the passed
|
|
* in buffer, to use the name! The implementation often starts at an offset
|
|
* into the buffer, and may leave 0 bytes at the start.
|
|
*
|
|
* "buflen" should be positive.
|
|
*/
|
|
char *d_path(const struct path *path, char *buf, int buflen)
|
|
{
|
|
char *res;
|
|
struct path root;
|
|
struct path tmp;
|
|
|
|
/*
|
|
* We have various synthetic filesystems that never get mounted. On
|
|
* these filesystems dentries are never used for lookup purposes, and
|
|
* thus don't need to be hashed. They also don't need a name until a
|
|
* user wants to identify the object in /proc/pid/fd/. The little hack
|
|
* below allows us to generate a name for these objects on demand:
|
|
*/
|
|
if (path->dentry->d_op && path->dentry->d_op->d_dname)
|
|
return path->dentry->d_op->d_dname(path->dentry, buf, buflen);
|
|
|
|
read_lock(¤t->fs->lock);
|
|
root = current->fs->root;
|
|
path_get(&root);
|
|
read_unlock(¤t->fs->lock);
|
|
spin_lock(&dcache_lock);
|
|
tmp = root;
|
|
res = __d_path(path, &tmp, buf, buflen);
|
|
spin_unlock(&dcache_lock);
|
|
path_put(&root);
|
|
return res;
|
|
}
|
|
|
|
/*
|
|
* Helper function for dentry_operations.d_dname() members
|
|
*/
|
|
char *dynamic_dname(struct dentry *dentry, char *buffer, int buflen,
|
|
const char *fmt, ...)
|
|
{
|
|
va_list args;
|
|
char temp[64];
|
|
int sz;
|
|
|
|
va_start(args, fmt);
|
|
sz = vsnprintf(temp, sizeof(temp), fmt, args) + 1;
|
|
va_end(args);
|
|
|
|
if (sz > sizeof(temp) || sz > buflen)
|
|
return ERR_PTR(-ENAMETOOLONG);
|
|
|
|
buffer += buflen - sz;
|
|
return memcpy(buffer, temp, sz);
|
|
}
|
|
|
|
/*
|
|
* Write full pathname from the root of the filesystem into the buffer.
|
|
*/
|
|
char *dentry_path(struct dentry *dentry, char *buf, int buflen)
|
|
{
|
|
char *end = buf + buflen;
|
|
char *retval;
|
|
|
|
spin_lock(&dcache_lock);
|
|
prepend(&end, &buflen, "\0", 1);
|
|
if (!IS_ROOT(dentry) && d_unhashed(dentry) &&
|
|
(prepend(&end, &buflen, "//deleted", 9) != 0))
|
|
goto Elong;
|
|
if (buflen < 1)
|
|
goto Elong;
|
|
/* Get '/' right */
|
|
retval = end-1;
|
|
*retval = '/';
|
|
|
|
while (!IS_ROOT(dentry)) {
|
|
struct dentry *parent = dentry->d_parent;
|
|
|
|
prefetch(parent);
|
|
if ((prepend_name(&end, &buflen, &dentry->d_name) != 0) ||
|
|
(prepend(&end, &buflen, "/", 1) != 0))
|
|
goto Elong;
|
|
|
|
retval = end;
|
|
dentry = parent;
|
|
}
|
|
spin_unlock(&dcache_lock);
|
|
return retval;
|
|
Elong:
|
|
spin_unlock(&dcache_lock);
|
|
return ERR_PTR(-ENAMETOOLONG);
|
|
}
|
|
|
|
/*
|
|
* NOTE! The user-level library version returns a
|
|
* character pointer. The kernel system call just
|
|
* returns the length of the buffer filled (which
|
|
* includes the ending '\0' character), or a negative
|
|
* error value. So libc would do something like
|
|
*
|
|
* char *getcwd(char * buf, size_t size)
|
|
* {
|
|
* int retval;
|
|
*
|
|
* retval = sys_getcwd(buf, size);
|
|
* if (retval >= 0)
|
|
* return buf;
|
|
* errno = -retval;
|
|
* return NULL;
|
|
* }
|
|
*/
|
|
SYSCALL_DEFINE2(getcwd, char __user *, buf, unsigned long, size)
|
|
{
|
|
int error;
|
|
struct path pwd, root;
|
|
char *page = (char *) __get_free_page(GFP_USER);
|
|
|
|
if (!page)
|
|
return -ENOMEM;
|
|
|
|
read_lock(¤t->fs->lock);
|
|
pwd = current->fs->pwd;
|
|
path_get(&pwd);
|
|
root = current->fs->root;
|
|
path_get(&root);
|
|
read_unlock(¤t->fs->lock);
|
|
|
|
error = -ENOENT;
|
|
/* Has the current directory has been unlinked? */
|
|
spin_lock(&dcache_lock);
|
|
if (IS_ROOT(pwd.dentry) || !d_unhashed(pwd.dentry)) {
|
|
unsigned long len;
|
|
struct path tmp = root;
|
|
char * cwd;
|
|
|
|
cwd = __d_path(&pwd, &tmp, page, PAGE_SIZE);
|
|
spin_unlock(&dcache_lock);
|
|
|
|
error = PTR_ERR(cwd);
|
|
if (IS_ERR(cwd))
|
|
goto out;
|
|
|
|
error = -ERANGE;
|
|
len = PAGE_SIZE + page - cwd;
|
|
if (len <= size) {
|
|
error = len;
|
|
if (copy_to_user(buf, cwd, len))
|
|
error = -EFAULT;
|
|
}
|
|
} else
|
|
spin_unlock(&dcache_lock);
|
|
|
|
out:
|
|
path_put(&pwd);
|
|
path_put(&root);
|
|
free_page((unsigned long) page);
|
|
return error;
|
|
}
|
|
|
|
/*
|
|
* Test whether new_dentry is a subdirectory of old_dentry.
|
|
*
|
|
* Trivially implemented using the dcache structure
|
|
*/
|
|
|
|
/**
|
|
* is_subdir - is new dentry a subdirectory of old_dentry
|
|
* @new_dentry: new dentry
|
|
* @old_dentry: old dentry
|
|
*
|
|
* Returns 1 if new_dentry is a subdirectory of the parent (at any depth).
|
|
* Returns 0 otherwise.
|
|
* Caller must ensure that "new_dentry" is pinned before calling is_subdir()
|
|
*/
|
|
|
|
int is_subdir(struct dentry *new_dentry, struct dentry *old_dentry)
|
|
{
|
|
int result;
|
|
unsigned long seq;
|
|
|
|
/* FIXME: This is old behavior, needed? Please check callers. */
|
|
if (new_dentry == old_dentry)
|
|
return 1;
|
|
|
|
/*
|
|
* Need rcu_readlock to protect against the d_parent trashing
|
|
* due to d_move
|
|
*/
|
|
rcu_read_lock();
|
|
do {
|
|
/* for restarting inner loop in case of seq retry */
|
|
seq = read_seqbegin(&rename_lock);
|
|
if (d_ancestor(old_dentry, new_dentry))
|
|
result = 1;
|
|
else
|
|
result = 0;
|
|
} while (read_seqretry(&rename_lock, seq));
|
|
rcu_read_unlock();
|
|
|
|
return result;
|
|
}
|
|
|
|
void d_genocide(struct dentry *root)
|
|
{
|
|
struct dentry *this_parent = root;
|
|
struct list_head *next;
|
|
|
|
spin_lock(&dcache_lock);
|
|
repeat:
|
|
next = this_parent->d_subdirs.next;
|
|
resume:
|
|
while (next != &this_parent->d_subdirs) {
|
|
struct list_head *tmp = next;
|
|
struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child);
|
|
next = tmp->next;
|
|
if (d_unhashed(dentry)||!dentry->d_inode)
|
|
continue;
|
|
if (!list_empty(&dentry->d_subdirs)) {
|
|
this_parent = dentry;
|
|
goto repeat;
|
|
}
|
|
atomic_dec(&dentry->d_count);
|
|
}
|
|
if (this_parent != root) {
|
|
next = this_parent->d_u.d_child.next;
|
|
atomic_dec(&this_parent->d_count);
|
|
this_parent = this_parent->d_parent;
|
|
goto resume;
|
|
}
|
|
spin_unlock(&dcache_lock);
|
|
}
|
|
|
|
/**
|
|
* find_inode_number - check for dentry with name
|
|
* @dir: directory to check
|
|
* @name: Name to find.
|
|
*
|
|
* Check whether a dentry already exists for the given name,
|
|
* and return the inode number if it has an inode. Otherwise
|
|
* 0 is returned.
|
|
*
|
|
* This routine is used to post-process directory listings for
|
|
* filesystems using synthetic inode numbers, and is necessary
|
|
* to keep getcwd() working.
|
|
*/
|
|
|
|
ino_t find_inode_number(struct dentry *dir, struct qstr *name)
|
|
{
|
|
struct dentry * dentry;
|
|
ino_t ino = 0;
|
|
|
|
dentry = d_hash_and_lookup(dir, name);
|
|
if (dentry) {
|
|
if (dentry->d_inode)
|
|
ino = dentry->d_inode->i_ino;
|
|
dput(dentry);
|
|
}
|
|
return ino;
|
|
}
|
|
|
|
static __initdata unsigned long dhash_entries;
|
|
static int __init set_dhash_entries(char *str)
|
|
{
|
|
if (!str)
|
|
return 0;
|
|
dhash_entries = simple_strtoul(str, &str, 0);
|
|
return 1;
|
|
}
|
|
__setup("dhash_entries=", set_dhash_entries);
|
|
|
|
static void __init dcache_init_early(void)
|
|
{
|
|
int loop;
|
|
|
|
/* If hashes are distributed across NUMA nodes, defer
|
|
* hash allocation until vmalloc space is available.
|
|
*/
|
|
if (hashdist)
|
|
return;
|
|
|
|
dentry_hashtable =
|
|
alloc_large_system_hash("Dentry cache",
|
|
sizeof(struct hlist_head),
|
|
dhash_entries,
|
|
13,
|
|
HASH_EARLY,
|
|
&d_hash_shift,
|
|
&d_hash_mask,
|
|
0);
|
|
|
|
for (loop = 0; loop < (1 << d_hash_shift); loop++)
|
|
INIT_HLIST_HEAD(&dentry_hashtable[loop]);
|
|
}
|
|
|
|
static void __init dcache_init(void)
|
|
{
|
|
int loop;
|
|
|
|
/*
|
|
* A constructor could be added for stable state like the lists,
|
|
* but it is probably not worth it because of the cache nature
|
|
* of the dcache.
|
|
*/
|
|
dentry_cache = KMEM_CACHE(dentry,
|
|
SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|SLAB_MEM_SPREAD);
|
|
|
|
register_shrinker(&dcache_shrinker);
|
|
|
|
/* Hash may have been set up in dcache_init_early */
|
|
if (!hashdist)
|
|
return;
|
|
|
|
dentry_hashtable =
|
|
alloc_large_system_hash("Dentry cache",
|
|
sizeof(struct hlist_head),
|
|
dhash_entries,
|
|
13,
|
|
0,
|
|
&d_hash_shift,
|
|
&d_hash_mask,
|
|
0);
|
|
|
|
for (loop = 0; loop < (1 << d_hash_shift); loop++)
|
|
INIT_HLIST_HEAD(&dentry_hashtable[loop]);
|
|
}
|
|
|
|
/* SLAB cache for __getname() consumers */
|
|
struct kmem_cache *names_cachep __read_mostly;
|
|
|
|
EXPORT_SYMBOL(d_genocide);
|
|
|
|
void __init vfs_caches_init_early(void)
|
|
{
|
|
dcache_init_early();
|
|
inode_init_early();
|
|
}
|
|
|
|
void __init vfs_caches_init(unsigned long mempages)
|
|
{
|
|
unsigned long reserve;
|
|
|
|
/* Base hash sizes on available memory, with a reserve equal to
|
|
150% of current kernel size */
|
|
|
|
reserve = min((mempages - nr_free_pages()) * 3/2, mempages - 1);
|
|
mempages -= reserve;
|
|
|
|
names_cachep = kmem_cache_create("names_cache", PATH_MAX, 0,
|
|
SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
|
|
|
|
dcache_init();
|
|
inode_init();
|
|
files_init(mempages);
|
|
mnt_init();
|
|
bdev_cache_init();
|
|
chrdev_init();
|
|
}
|
|
|
|
EXPORT_SYMBOL(d_alloc);
|
|
EXPORT_SYMBOL(d_alloc_root);
|
|
EXPORT_SYMBOL(d_delete);
|
|
EXPORT_SYMBOL(d_find_alias);
|
|
EXPORT_SYMBOL(d_instantiate);
|
|
EXPORT_SYMBOL(d_invalidate);
|
|
EXPORT_SYMBOL(d_lookup);
|
|
EXPORT_SYMBOL(d_move);
|
|
EXPORT_SYMBOL_GPL(d_materialise_unique);
|
|
EXPORT_SYMBOL(d_path);
|
|
EXPORT_SYMBOL(d_prune_aliases);
|
|
EXPORT_SYMBOL(d_rehash);
|
|
EXPORT_SYMBOL(d_splice_alias);
|
|
EXPORT_SYMBOL(d_add_ci);
|
|
EXPORT_SYMBOL(d_validate);
|
|
EXPORT_SYMBOL(dget_locked);
|
|
EXPORT_SYMBOL(dput);
|
|
EXPORT_SYMBOL(find_inode_number);
|
|
EXPORT_SYMBOL(have_submounts);
|
|
EXPORT_SYMBOL(names_cachep);
|
|
EXPORT_SYMBOL(shrink_dcache_parent);
|
|
EXPORT_SYMBOL(shrink_dcache_sb);
|