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eb6ef3df4f
I've noticed significant locking contention in memory reclaimer around sb_lock inside grab_super_passive(). Grab_super_passive() is called from two places: in icache/dcache shrinkers (function super_cache_scan) and from writeback (function __writeback_inodes_wb). Both are required for progress in memory allocator. Grab_super_passive() acquires sb_lock to increment sb->s_count and check sb->s_instances. It seems sb->s_umount locked for read is enough here: super-block deactivation always runs under sb->s_umount locked for write. Protecting super-block itself isn't a problem: in super_cache_scan() sb is protected by shrinker_rwsem: it cannot be freed if its slab shrinkers are still active. Inside writeback super-block comes from inode from bdi writeback list under wb->list_lock. This patch removes locking sb_lock and checks s_instances under s_umount: generic_shutdown_super() unlinks it under sb->s_umount locked for write. New variant is called trylock_super() and since it only locks semaphore, callers must call up_read(&sb->s_umount) instead of drop_super(sb) when they're done. Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
1397 lines
35 KiB
C
1397 lines
35 KiB
C
/*
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* linux/fs/super.c
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*
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* Copyright (C) 1991, 1992 Linus Torvalds
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*
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* super.c contains code to handle: - mount structures
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* - super-block tables
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* - filesystem drivers list
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* - mount system call
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* - umount system call
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* - ustat system call
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*
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* GK 2/5/95 - Changed to support mounting the root fs via NFS
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*
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* Added kerneld support: Jacques Gelinas and Bjorn Ekwall
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* Added change_root: Werner Almesberger & Hans Lermen, Feb '96
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* Added options to /proc/mounts:
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* Torbjörn Lindh (torbjorn.lindh@gopta.se), April 14, 1996.
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* Added devfs support: Richard Gooch <rgooch@atnf.csiro.au>, 13-JAN-1998
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* Heavily rewritten for 'one fs - one tree' dcache architecture. AV, Mar 2000
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*/
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#include <linux/export.h>
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#include <linux/slab.h>
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#include <linux/blkdev.h>
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#include <linux/mount.h>
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#include <linux/security.h>
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#include <linux/writeback.h> /* for the emergency remount stuff */
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#include <linux/idr.h>
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#include <linux/mutex.h>
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#include <linux/backing-dev.h>
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#include <linux/rculist_bl.h>
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#include <linux/cleancache.h>
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#include <linux/fsnotify.h>
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#include <linux/lockdep.h>
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#include "internal.h"
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static LIST_HEAD(super_blocks);
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static DEFINE_SPINLOCK(sb_lock);
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static char *sb_writers_name[SB_FREEZE_LEVELS] = {
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"sb_writers",
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"sb_pagefaults",
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"sb_internal",
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};
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/*
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* One thing we have to be careful of with a per-sb shrinker is that we don't
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* drop the last active reference to the superblock from within the shrinker.
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* If that happens we could trigger unregistering the shrinker from within the
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* shrinker path and that leads to deadlock on the shrinker_rwsem. Hence we
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* take a passive reference to the superblock to avoid this from occurring.
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*/
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static unsigned long super_cache_scan(struct shrinker *shrink,
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struct shrink_control *sc)
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{
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struct super_block *sb;
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long fs_objects = 0;
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long total_objects;
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long freed = 0;
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long dentries;
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long inodes;
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sb = container_of(shrink, struct super_block, s_shrink);
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/*
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* Deadlock avoidance. We may hold various FS locks, and we don't want
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* to recurse into the FS that called us in clear_inode() and friends..
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*/
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if (!(sc->gfp_mask & __GFP_FS))
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return SHRINK_STOP;
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if (!trylock_super(sb))
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return SHRINK_STOP;
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if (sb->s_op->nr_cached_objects)
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fs_objects = sb->s_op->nr_cached_objects(sb, sc);
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inodes = list_lru_shrink_count(&sb->s_inode_lru, sc);
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dentries = list_lru_shrink_count(&sb->s_dentry_lru, sc);
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total_objects = dentries + inodes + fs_objects + 1;
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if (!total_objects)
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total_objects = 1;
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/* proportion the scan between the caches */
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dentries = mult_frac(sc->nr_to_scan, dentries, total_objects);
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inodes = mult_frac(sc->nr_to_scan, inodes, total_objects);
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fs_objects = mult_frac(sc->nr_to_scan, fs_objects, total_objects);
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/*
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* prune the dcache first as the icache is pinned by it, then
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* prune the icache, followed by the filesystem specific caches
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*
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* Ensure that we always scan at least one object - memcg kmem
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* accounting uses this to fully empty the caches.
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*/
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sc->nr_to_scan = dentries + 1;
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freed = prune_dcache_sb(sb, sc);
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sc->nr_to_scan = inodes + 1;
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freed += prune_icache_sb(sb, sc);
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if (fs_objects) {
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sc->nr_to_scan = fs_objects + 1;
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freed += sb->s_op->free_cached_objects(sb, sc);
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}
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up_read(&sb->s_umount);
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return freed;
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}
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static unsigned long super_cache_count(struct shrinker *shrink,
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struct shrink_control *sc)
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{
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struct super_block *sb;
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long total_objects = 0;
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sb = container_of(shrink, struct super_block, s_shrink);
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/*
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* Don't call trylock_super as it is a potential
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* scalability bottleneck. The counts could get updated
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* between super_cache_count and super_cache_scan anyway.
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* Call to super_cache_count with shrinker_rwsem held
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* ensures the safety of call to list_lru_shrink_count() and
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* s_op->nr_cached_objects().
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*/
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if (sb->s_op && sb->s_op->nr_cached_objects)
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total_objects = sb->s_op->nr_cached_objects(sb, sc);
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total_objects += list_lru_shrink_count(&sb->s_dentry_lru, sc);
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total_objects += list_lru_shrink_count(&sb->s_inode_lru, sc);
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total_objects = vfs_pressure_ratio(total_objects);
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return total_objects;
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}
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/**
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* destroy_super - frees a superblock
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* @s: superblock to free
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*
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* Frees a superblock.
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*/
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static void destroy_super(struct super_block *s)
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{
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int i;
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list_lru_destroy(&s->s_dentry_lru);
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list_lru_destroy(&s->s_inode_lru);
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for (i = 0; i < SB_FREEZE_LEVELS; i++)
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percpu_counter_destroy(&s->s_writers.counter[i]);
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security_sb_free(s);
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WARN_ON(!list_empty(&s->s_mounts));
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kfree(s->s_subtype);
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kfree(s->s_options);
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kfree_rcu(s, rcu);
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}
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/**
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* alloc_super - create new superblock
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* @type: filesystem type superblock should belong to
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* @flags: the mount flags
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*
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* Allocates and initializes a new &struct super_block. alloc_super()
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* returns a pointer new superblock or %NULL if allocation had failed.
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*/
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static struct super_block *alloc_super(struct file_system_type *type, int flags)
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{
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struct super_block *s = kzalloc(sizeof(struct super_block), GFP_USER);
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static const struct super_operations default_op;
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int i;
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if (!s)
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return NULL;
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INIT_LIST_HEAD(&s->s_mounts);
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if (security_sb_alloc(s))
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goto fail;
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for (i = 0; i < SB_FREEZE_LEVELS; i++) {
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if (percpu_counter_init(&s->s_writers.counter[i], 0,
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GFP_KERNEL) < 0)
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goto fail;
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lockdep_init_map(&s->s_writers.lock_map[i], sb_writers_name[i],
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&type->s_writers_key[i], 0);
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}
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init_waitqueue_head(&s->s_writers.wait);
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init_waitqueue_head(&s->s_writers.wait_unfrozen);
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s->s_bdi = &noop_backing_dev_info;
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s->s_flags = flags;
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INIT_HLIST_NODE(&s->s_instances);
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INIT_HLIST_BL_HEAD(&s->s_anon);
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INIT_LIST_HEAD(&s->s_inodes);
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if (list_lru_init_memcg(&s->s_dentry_lru))
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goto fail;
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if (list_lru_init_memcg(&s->s_inode_lru))
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goto fail;
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init_rwsem(&s->s_umount);
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lockdep_set_class(&s->s_umount, &type->s_umount_key);
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/*
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* sget() can have s_umount recursion.
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*
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* When it cannot find a suitable sb, it allocates a new
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* one (this one), and tries again to find a suitable old
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* one.
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*
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* In case that succeeds, it will acquire the s_umount
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* lock of the old one. Since these are clearly distrinct
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* locks, and this object isn't exposed yet, there's no
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* risk of deadlocks.
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*
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* Annotate this by putting this lock in a different
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* subclass.
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*/
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down_write_nested(&s->s_umount, SINGLE_DEPTH_NESTING);
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s->s_count = 1;
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atomic_set(&s->s_active, 1);
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mutex_init(&s->s_vfs_rename_mutex);
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lockdep_set_class(&s->s_vfs_rename_mutex, &type->s_vfs_rename_key);
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mutex_init(&s->s_dquot.dqio_mutex);
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mutex_init(&s->s_dquot.dqonoff_mutex);
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s->s_maxbytes = MAX_NON_LFS;
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s->s_op = &default_op;
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s->s_time_gran = 1000000000;
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s->cleancache_poolid = -1;
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s->s_shrink.seeks = DEFAULT_SEEKS;
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s->s_shrink.scan_objects = super_cache_scan;
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s->s_shrink.count_objects = super_cache_count;
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s->s_shrink.batch = 1024;
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s->s_shrink.flags = SHRINKER_NUMA_AWARE | SHRINKER_MEMCG_AWARE;
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return s;
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fail:
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destroy_super(s);
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return NULL;
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}
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/* Superblock refcounting */
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/*
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* Drop a superblock's refcount. The caller must hold sb_lock.
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*/
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static void __put_super(struct super_block *sb)
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{
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if (!--sb->s_count) {
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list_del_init(&sb->s_list);
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destroy_super(sb);
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}
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}
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/**
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* put_super - drop a temporary reference to superblock
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* @sb: superblock in question
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*
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* Drops a temporary reference, frees superblock if there's no
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* references left.
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*/
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static void put_super(struct super_block *sb)
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{
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spin_lock(&sb_lock);
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__put_super(sb);
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spin_unlock(&sb_lock);
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}
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/**
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* deactivate_locked_super - drop an active reference to superblock
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* @s: superblock to deactivate
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*
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* Drops an active reference to superblock, converting it into a temprory
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* one if there is no other active references left. In that case we
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* tell fs driver to shut it down and drop the temporary reference we
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* had just acquired.
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*
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* Caller holds exclusive lock on superblock; that lock is released.
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*/
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void deactivate_locked_super(struct super_block *s)
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{
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struct file_system_type *fs = s->s_type;
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if (atomic_dec_and_test(&s->s_active)) {
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cleancache_invalidate_fs(s);
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unregister_shrinker(&s->s_shrink);
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fs->kill_sb(s);
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/*
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* Since list_lru_destroy() may sleep, we cannot call it from
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* put_super(), where we hold the sb_lock. Therefore we destroy
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* the lru lists right now.
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*/
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list_lru_destroy(&s->s_dentry_lru);
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list_lru_destroy(&s->s_inode_lru);
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put_filesystem(fs);
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put_super(s);
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} else {
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up_write(&s->s_umount);
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}
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}
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EXPORT_SYMBOL(deactivate_locked_super);
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/**
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* deactivate_super - drop an active reference to superblock
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* @s: superblock to deactivate
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*
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* Variant of deactivate_locked_super(), except that superblock is *not*
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* locked by caller. If we are going to drop the final active reference,
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* lock will be acquired prior to that.
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*/
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void deactivate_super(struct super_block *s)
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{
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if (!atomic_add_unless(&s->s_active, -1, 1)) {
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down_write(&s->s_umount);
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deactivate_locked_super(s);
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}
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}
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EXPORT_SYMBOL(deactivate_super);
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/**
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* grab_super - acquire an active reference
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* @s: reference we are trying to make active
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*
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* Tries to acquire an active reference. grab_super() is used when we
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* had just found a superblock in super_blocks or fs_type->fs_supers
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* and want to turn it into a full-blown active reference. grab_super()
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* is called with sb_lock held and drops it. Returns 1 in case of
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* success, 0 if we had failed (superblock contents was already dead or
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* dying when grab_super() had been called). Note that this is only
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* called for superblocks not in rundown mode (== ones still on ->fs_supers
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* of their type), so increment of ->s_count is OK here.
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*/
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static int grab_super(struct super_block *s) __releases(sb_lock)
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{
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s->s_count++;
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spin_unlock(&sb_lock);
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down_write(&s->s_umount);
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if ((s->s_flags & MS_BORN) && atomic_inc_not_zero(&s->s_active)) {
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put_super(s);
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return 1;
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}
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up_write(&s->s_umount);
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put_super(s);
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return 0;
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}
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/*
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* trylock_super - try to grab ->s_umount shared
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* @sb: reference we are trying to grab
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*
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* Try to prevent fs shutdown. This is used in places where we
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* cannot take an active reference but we need to ensure that the
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* filesystem is not shut down while we are working on it. It returns
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* false if we cannot acquire s_umount or if we lose the race and
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* filesystem already got into shutdown, and returns true with the s_umount
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* lock held in read mode in case of success. On successful return,
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* the caller must drop the s_umount lock when done.
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*
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* Note that unlike get_super() et.al. this one does *not* bump ->s_count.
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* The reason why it's safe is that we are OK with doing trylock instead
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* of down_read(). There's a couple of places that are OK with that, but
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* it's very much not a general-purpose interface.
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*/
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bool trylock_super(struct super_block *sb)
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{
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if (down_read_trylock(&sb->s_umount)) {
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if (!hlist_unhashed(&sb->s_instances) &&
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sb->s_root && (sb->s_flags & MS_BORN))
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return true;
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up_read(&sb->s_umount);
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}
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return false;
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}
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/**
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* generic_shutdown_super - common helper for ->kill_sb()
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* @sb: superblock to kill
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*
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* generic_shutdown_super() does all fs-independent work on superblock
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* shutdown. Typical ->kill_sb() should pick all fs-specific objects
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* that need destruction out of superblock, call generic_shutdown_super()
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* and release aforementioned objects. Note: dentries and inodes _are_
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* taken care of and do not need specific handling.
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*
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* Upon calling this function, the filesystem may no longer alter or
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* rearrange the set of dentries belonging to this super_block, nor may it
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* change the attachments of dentries to inodes.
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*/
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void generic_shutdown_super(struct super_block *sb)
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{
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const struct super_operations *sop = sb->s_op;
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|
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if (sb->s_root) {
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shrink_dcache_for_umount(sb);
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sync_filesystem(sb);
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sb->s_flags &= ~MS_ACTIVE;
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|
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fsnotify_unmount_inodes(&sb->s_inodes);
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|
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evict_inodes(sb);
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|
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if (sb->s_dio_done_wq) {
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destroy_workqueue(sb->s_dio_done_wq);
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sb->s_dio_done_wq = NULL;
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}
|
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|
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if (sop->put_super)
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sop->put_super(sb);
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|
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if (!list_empty(&sb->s_inodes)) {
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printk("VFS: Busy inodes after unmount of %s. "
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"Self-destruct in 5 seconds. Have a nice day...\n",
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sb->s_id);
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}
|
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}
|
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spin_lock(&sb_lock);
|
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/* should be initialized for __put_super_and_need_restart() */
|
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hlist_del_init(&sb->s_instances);
|
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spin_unlock(&sb_lock);
|
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up_write(&sb->s_umount);
|
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}
|
|
|
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EXPORT_SYMBOL(generic_shutdown_super);
|
|
|
|
/**
|
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* sget - find or create a superblock
|
|
* @type: filesystem type superblock should belong to
|
|
* @test: comparison callback
|
|
* @set: setup callback
|
|
* @flags: mount flags
|
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* @data: argument to each of them
|
|
*/
|
|
struct super_block *sget(struct file_system_type *type,
|
|
int (*test)(struct super_block *,void *),
|
|
int (*set)(struct super_block *,void *),
|
|
int flags,
|
|
void *data)
|
|
{
|
|
struct super_block *s = NULL;
|
|
struct super_block *old;
|
|
int err;
|
|
|
|
retry:
|
|
spin_lock(&sb_lock);
|
|
if (test) {
|
|
hlist_for_each_entry(old, &type->fs_supers, s_instances) {
|
|
if (!test(old, data))
|
|
continue;
|
|
if (!grab_super(old))
|
|
goto retry;
|
|
if (s) {
|
|
up_write(&s->s_umount);
|
|
destroy_super(s);
|
|
s = NULL;
|
|
}
|
|
return old;
|
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}
|
|
}
|
|
if (!s) {
|
|
spin_unlock(&sb_lock);
|
|
s = alloc_super(type, flags);
|
|
if (!s)
|
|
return ERR_PTR(-ENOMEM);
|
|
goto retry;
|
|
}
|
|
|
|
err = set(s, data);
|
|
if (err) {
|
|
spin_unlock(&sb_lock);
|
|
up_write(&s->s_umount);
|
|
destroy_super(s);
|
|
return ERR_PTR(err);
|
|
}
|
|
s->s_type = type;
|
|
strlcpy(s->s_id, type->name, sizeof(s->s_id));
|
|
list_add_tail(&s->s_list, &super_blocks);
|
|
hlist_add_head(&s->s_instances, &type->fs_supers);
|
|
spin_unlock(&sb_lock);
|
|
get_filesystem(type);
|
|
register_shrinker(&s->s_shrink);
|
|
return s;
|
|
}
|
|
|
|
EXPORT_SYMBOL(sget);
|
|
|
|
void drop_super(struct super_block *sb)
|
|
{
|
|
up_read(&sb->s_umount);
|
|
put_super(sb);
|
|
}
|
|
|
|
EXPORT_SYMBOL(drop_super);
|
|
|
|
/**
|
|
* iterate_supers - call function for all active superblocks
|
|
* @f: function to call
|
|
* @arg: argument to pass to it
|
|
*
|
|
* Scans the superblock list and calls given function, passing it
|
|
* locked superblock and given argument.
|
|
*/
|
|
void iterate_supers(void (*f)(struct super_block *, void *), void *arg)
|
|
{
|
|
struct super_block *sb, *p = NULL;
|
|
|
|
spin_lock(&sb_lock);
|
|
list_for_each_entry(sb, &super_blocks, s_list) {
|
|
if (hlist_unhashed(&sb->s_instances))
|
|
continue;
|
|
sb->s_count++;
|
|
spin_unlock(&sb_lock);
|
|
|
|
down_read(&sb->s_umount);
|
|
if (sb->s_root && (sb->s_flags & MS_BORN))
|
|
f(sb, arg);
|
|
up_read(&sb->s_umount);
|
|
|
|
spin_lock(&sb_lock);
|
|
if (p)
|
|
__put_super(p);
|
|
p = sb;
|
|
}
|
|
if (p)
|
|
__put_super(p);
|
|
spin_unlock(&sb_lock);
|
|
}
|
|
|
|
/**
|
|
* iterate_supers_type - call function for superblocks of given type
|
|
* @type: fs type
|
|
* @f: function to call
|
|
* @arg: argument to pass to it
|
|
*
|
|
* Scans the superblock list and calls given function, passing it
|
|
* locked superblock and given argument.
|
|
*/
|
|
void iterate_supers_type(struct file_system_type *type,
|
|
void (*f)(struct super_block *, void *), void *arg)
|
|
{
|
|
struct super_block *sb, *p = NULL;
|
|
|
|
spin_lock(&sb_lock);
|
|
hlist_for_each_entry(sb, &type->fs_supers, s_instances) {
|
|
sb->s_count++;
|
|
spin_unlock(&sb_lock);
|
|
|
|
down_read(&sb->s_umount);
|
|
if (sb->s_root && (sb->s_flags & MS_BORN))
|
|
f(sb, arg);
|
|
up_read(&sb->s_umount);
|
|
|
|
spin_lock(&sb_lock);
|
|
if (p)
|
|
__put_super(p);
|
|
p = sb;
|
|
}
|
|
if (p)
|
|
__put_super(p);
|
|
spin_unlock(&sb_lock);
|
|
}
|
|
|
|
EXPORT_SYMBOL(iterate_supers_type);
|
|
|
|
/**
|
|
* get_super - get the superblock of a device
|
|
* @bdev: device to get the superblock for
|
|
*
|
|
* Scans the superblock list and finds the superblock of the file system
|
|
* mounted on the device given. %NULL is returned if no match is found.
|
|
*/
|
|
|
|
struct super_block *get_super(struct block_device *bdev)
|
|
{
|
|
struct super_block *sb;
|
|
|
|
if (!bdev)
|
|
return NULL;
|
|
|
|
spin_lock(&sb_lock);
|
|
rescan:
|
|
list_for_each_entry(sb, &super_blocks, s_list) {
|
|
if (hlist_unhashed(&sb->s_instances))
|
|
continue;
|
|
if (sb->s_bdev == bdev) {
|
|
sb->s_count++;
|
|
spin_unlock(&sb_lock);
|
|
down_read(&sb->s_umount);
|
|
/* still alive? */
|
|
if (sb->s_root && (sb->s_flags & MS_BORN))
|
|
return sb;
|
|
up_read(&sb->s_umount);
|
|
/* nope, got unmounted */
|
|
spin_lock(&sb_lock);
|
|
__put_super(sb);
|
|
goto rescan;
|
|
}
|
|
}
|
|
spin_unlock(&sb_lock);
|
|
return NULL;
|
|
}
|
|
|
|
EXPORT_SYMBOL(get_super);
|
|
|
|
/**
|
|
* get_super_thawed - get thawed superblock of a device
|
|
* @bdev: device to get the superblock for
|
|
*
|
|
* Scans the superblock list and finds the superblock of the file system
|
|
* mounted on the device. The superblock is returned once it is thawed
|
|
* (or immediately if it was not frozen). %NULL is returned if no match
|
|
* is found.
|
|
*/
|
|
struct super_block *get_super_thawed(struct block_device *bdev)
|
|
{
|
|
while (1) {
|
|
struct super_block *s = get_super(bdev);
|
|
if (!s || s->s_writers.frozen == SB_UNFROZEN)
|
|
return s;
|
|
up_read(&s->s_umount);
|
|
wait_event(s->s_writers.wait_unfrozen,
|
|
s->s_writers.frozen == SB_UNFROZEN);
|
|
put_super(s);
|
|
}
|
|
}
|
|
EXPORT_SYMBOL(get_super_thawed);
|
|
|
|
/**
|
|
* get_active_super - get an active reference to the superblock of a device
|
|
* @bdev: device to get the superblock for
|
|
*
|
|
* Scans the superblock list and finds the superblock of the file system
|
|
* mounted on the device given. Returns the superblock with an active
|
|
* reference or %NULL if none was found.
|
|
*/
|
|
struct super_block *get_active_super(struct block_device *bdev)
|
|
{
|
|
struct super_block *sb;
|
|
|
|
if (!bdev)
|
|
return NULL;
|
|
|
|
restart:
|
|
spin_lock(&sb_lock);
|
|
list_for_each_entry(sb, &super_blocks, s_list) {
|
|
if (hlist_unhashed(&sb->s_instances))
|
|
continue;
|
|
if (sb->s_bdev == bdev) {
|
|
if (!grab_super(sb))
|
|
goto restart;
|
|
up_write(&sb->s_umount);
|
|
return sb;
|
|
}
|
|
}
|
|
spin_unlock(&sb_lock);
|
|
return NULL;
|
|
}
|
|
|
|
struct super_block *user_get_super(dev_t dev)
|
|
{
|
|
struct super_block *sb;
|
|
|
|
spin_lock(&sb_lock);
|
|
rescan:
|
|
list_for_each_entry(sb, &super_blocks, s_list) {
|
|
if (hlist_unhashed(&sb->s_instances))
|
|
continue;
|
|
if (sb->s_dev == dev) {
|
|
sb->s_count++;
|
|
spin_unlock(&sb_lock);
|
|
down_read(&sb->s_umount);
|
|
/* still alive? */
|
|
if (sb->s_root && (sb->s_flags & MS_BORN))
|
|
return sb;
|
|
up_read(&sb->s_umount);
|
|
/* nope, got unmounted */
|
|
spin_lock(&sb_lock);
|
|
__put_super(sb);
|
|
goto rescan;
|
|
}
|
|
}
|
|
spin_unlock(&sb_lock);
|
|
return NULL;
|
|
}
|
|
|
|
/**
|
|
* do_remount_sb - asks filesystem to change mount options.
|
|
* @sb: superblock in question
|
|
* @flags: numeric part of options
|
|
* @data: the rest of options
|
|
* @force: whether or not to force the change
|
|
*
|
|
* Alters the mount options of a mounted file system.
|
|
*/
|
|
int do_remount_sb(struct super_block *sb, int flags, void *data, int force)
|
|
{
|
|
int retval;
|
|
int remount_ro;
|
|
|
|
if (sb->s_writers.frozen != SB_UNFROZEN)
|
|
return -EBUSY;
|
|
|
|
#ifdef CONFIG_BLOCK
|
|
if (!(flags & MS_RDONLY) && bdev_read_only(sb->s_bdev))
|
|
return -EACCES;
|
|
#endif
|
|
|
|
remount_ro = (flags & MS_RDONLY) && !(sb->s_flags & MS_RDONLY);
|
|
|
|
if (remount_ro) {
|
|
if (!hlist_empty(&sb->s_pins)) {
|
|
up_write(&sb->s_umount);
|
|
group_pin_kill(&sb->s_pins);
|
|
down_write(&sb->s_umount);
|
|
if (!sb->s_root)
|
|
return 0;
|
|
if (sb->s_writers.frozen != SB_UNFROZEN)
|
|
return -EBUSY;
|
|
remount_ro = (flags & MS_RDONLY) && !(sb->s_flags & MS_RDONLY);
|
|
}
|
|
}
|
|
shrink_dcache_sb(sb);
|
|
|
|
/* If we are remounting RDONLY and current sb is read/write,
|
|
make sure there are no rw files opened */
|
|
if (remount_ro) {
|
|
if (force) {
|
|
sb->s_readonly_remount = 1;
|
|
smp_wmb();
|
|
} else {
|
|
retval = sb_prepare_remount_readonly(sb);
|
|
if (retval)
|
|
return retval;
|
|
}
|
|
}
|
|
|
|
if (sb->s_op->remount_fs) {
|
|
retval = sb->s_op->remount_fs(sb, &flags, data);
|
|
if (retval) {
|
|
if (!force)
|
|
goto cancel_readonly;
|
|
/* If forced remount, go ahead despite any errors */
|
|
WARN(1, "forced remount of a %s fs returned %i\n",
|
|
sb->s_type->name, retval);
|
|
}
|
|
}
|
|
sb->s_flags = (sb->s_flags & ~MS_RMT_MASK) | (flags & MS_RMT_MASK);
|
|
/* Needs to be ordered wrt mnt_is_readonly() */
|
|
smp_wmb();
|
|
sb->s_readonly_remount = 0;
|
|
|
|
/*
|
|
* Some filesystems modify their metadata via some other path than the
|
|
* bdev buffer cache (eg. use a private mapping, or directories in
|
|
* pagecache, etc). Also file data modifications go via their own
|
|
* mappings. So If we try to mount readonly then copy the filesystem
|
|
* from bdev, we could get stale data, so invalidate it to give a best
|
|
* effort at coherency.
|
|
*/
|
|
if (remount_ro && sb->s_bdev)
|
|
invalidate_bdev(sb->s_bdev);
|
|
return 0;
|
|
|
|
cancel_readonly:
|
|
sb->s_readonly_remount = 0;
|
|
return retval;
|
|
}
|
|
|
|
static void do_emergency_remount(struct work_struct *work)
|
|
{
|
|
struct super_block *sb, *p = NULL;
|
|
|
|
spin_lock(&sb_lock);
|
|
list_for_each_entry(sb, &super_blocks, s_list) {
|
|
if (hlist_unhashed(&sb->s_instances))
|
|
continue;
|
|
sb->s_count++;
|
|
spin_unlock(&sb_lock);
|
|
down_write(&sb->s_umount);
|
|
if (sb->s_root && sb->s_bdev && (sb->s_flags & MS_BORN) &&
|
|
!(sb->s_flags & MS_RDONLY)) {
|
|
/*
|
|
* What lock protects sb->s_flags??
|
|
*/
|
|
do_remount_sb(sb, MS_RDONLY, NULL, 1);
|
|
}
|
|
up_write(&sb->s_umount);
|
|
spin_lock(&sb_lock);
|
|
if (p)
|
|
__put_super(p);
|
|
p = sb;
|
|
}
|
|
if (p)
|
|
__put_super(p);
|
|
spin_unlock(&sb_lock);
|
|
kfree(work);
|
|
printk("Emergency Remount complete\n");
|
|
}
|
|
|
|
void emergency_remount(void)
|
|
{
|
|
struct work_struct *work;
|
|
|
|
work = kmalloc(sizeof(*work), GFP_ATOMIC);
|
|
if (work) {
|
|
INIT_WORK(work, do_emergency_remount);
|
|
schedule_work(work);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Unnamed block devices are dummy devices used by virtual
|
|
* filesystems which don't use real block-devices. -- jrs
|
|
*/
|
|
|
|
static DEFINE_IDA(unnamed_dev_ida);
|
|
static DEFINE_SPINLOCK(unnamed_dev_lock);/* protects the above */
|
|
/* Many userspace utilities consider an FSID of 0 invalid.
|
|
* Always return at least 1 from get_anon_bdev.
|
|
*/
|
|
static int unnamed_dev_start = 1;
|
|
|
|
int get_anon_bdev(dev_t *p)
|
|
{
|
|
int dev;
|
|
int error;
|
|
|
|
retry:
|
|
if (ida_pre_get(&unnamed_dev_ida, GFP_ATOMIC) == 0)
|
|
return -ENOMEM;
|
|
spin_lock(&unnamed_dev_lock);
|
|
error = ida_get_new_above(&unnamed_dev_ida, unnamed_dev_start, &dev);
|
|
if (!error)
|
|
unnamed_dev_start = dev + 1;
|
|
spin_unlock(&unnamed_dev_lock);
|
|
if (error == -EAGAIN)
|
|
/* We raced and lost with another CPU. */
|
|
goto retry;
|
|
else if (error)
|
|
return -EAGAIN;
|
|
|
|
if (dev == (1 << MINORBITS)) {
|
|
spin_lock(&unnamed_dev_lock);
|
|
ida_remove(&unnamed_dev_ida, dev);
|
|
if (unnamed_dev_start > dev)
|
|
unnamed_dev_start = dev;
|
|
spin_unlock(&unnamed_dev_lock);
|
|
return -EMFILE;
|
|
}
|
|
*p = MKDEV(0, dev & MINORMASK);
|
|
return 0;
|
|
}
|
|
EXPORT_SYMBOL(get_anon_bdev);
|
|
|
|
void free_anon_bdev(dev_t dev)
|
|
{
|
|
int slot = MINOR(dev);
|
|
spin_lock(&unnamed_dev_lock);
|
|
ida_remove(&unnamed_dev_ida, slot);
|
|
if (slot < unnamed_dev_start)
|
|
unnamed_dev_start = slot;
|
|
spin_unlock(&unnamed_dev_lock);
|
|
}
|
|
EXPORT_SYMBOL(free_anon_bdev);
|
|
|
|
int set_anon_super(struct super_block *s, void *data)
|
|
{
|
|
return get_anon_bdev(&s->s_dev);
|
|
}
|
|
|
|
EXPORT_SYMBOL(set_anon_super);
|
|
|
|
void kill_anon_super(struct super_block *sb)
|
|
{
|
|
dev_t dev = sb->s_dev;
|
|
generic_shutdown_super(sb);
|
|
free_anon_bdev(dev);
|
|
}
|
|
|
|
EXPORT_SYMBOL(kill_anon_super);
|
|
|
|
void kill_litter_super(struct super_block *sb)
|
|
{
|
|
if (sb->s_root)
|
|
d_genocide(sb->s_root);
|
|
kill_anon_super(sb);
|
|
}
|
|
|
|
EXPORT_SYMBOL(kill_litter_super);
|
|
|
|
static int ns_test_super(struct super_block *sb, void *data)
|
|
{
|
|
return sb->s_fs_info == data;
|
|
}
|
|
|
|
static int ns_set_super(struct super_block *sb, void *data)
|
|
{
|
|
sb->s_fs_info = data;
|
|
return set_anon_super(sb, NULL);
|
|
}
|
|
|
|
struct dentry *mount_ns(struct file_system_type *fs_type, int flags,
|
|
void *data, int (*fill_super)(struct super_block *, void *, int))
|
|
{
|
|
struct super_block *sb;
|
|
|
|
sb = sget(fs_type, ns_test_super, ns_set_super, flags, data);
|
|
if (IS_ERR(sb))
|
|
return ERR_CAST(sb);
|
|
|
|
if (!sb->s_root) {
|
|
int err;
|
|
err = fill_super(sb, data, flags & MS_SILENT ? 1 : 0);
|
|
if (err) {
|
|
deactivate_locked_super(sb);
|
|
return ERR_PTR(err);
|
|
}
|
|
|
|
sb->s_flags |= MS_ACTIVE;
|
|
}
|
|
|
|
return dget(sb->s_root);
|
|
}
|
|
|
|
EXPORT_SYMBOL(mount_ns);
|
|
|
|
#ifdef CONFIG_BLOCK
|
|
static int set_bdev_super(struct super_block *s, void *data)
|
|
{
|
|
s->s_bdev = data;
|
|
s->s_dev = s->s_bdev->bd_dev;
|
|
|
|
/*
|
|
* We set the bdi here to the queue backing, file systems can
|
|
* overwrite this in ->fill_super()
|
|
*/
|
|
s->s_bdi = &bdev_get_queue(s->s_bdev)->backing_dev_info;
|
|
return 0;
|
|
}
|
|
|
|
static int test_bdev_super(struct super_block *s, void *data)
|
|
{
|
|
return (void *)s->s_bdev == data;
|
|
}
|
|
|
|
struct dentry *mount_bdev(struct file_system_type *fs_type,
|
|
int flags, const char *dev_name, void *data,
|
|
int (*fill_super)(struct super_block *, void *, int))
|
|
{
|
|
struct block_device *bdev;
|
|
struct super_block *s;
|
|
fmode_t mode = FMODE_READ | FMODE_EXCL;
|
|
int error = 0;
|
|
|
|
if (!(flags & MS_RDONLY))
|
|
mode |= FMODE_WRITE;
|
|
|
|
bdev = blkdev_get_by_path(dev_name, mode, fs_type);
|
|
if (IS_ERR(bdev))
|
|
return ERR_CAST(bdev);
|
|
|
|
/*
|
|
* once the super is inserted into the list by sget, s_umount
|
|
* will protect the lockfs code from trying to start a snapshot
|
|
* while we are mounting
|
|
*/
|
|
mutex_lock(&bdev->bd_fsfreeze_mutex);
|
|
if (bdev->bd_fsfreeze_count > 0) {
|
|
mutex_unlock(&bdev->bd_fsfreeze_mutex);
|
|
error = -EBUSY;
|
|
goto error_bdev;
|
|
}
|
|
s = sget(fs_type, test_bdev_super, set_bdev_super, flags | MS_NOSEC,
|
|
bdev);
|
|
mutex_unlock(&bdev->bd_fsfreeze_mutex);
|
|
if (IS_ERR(s))
|
|
goto error_s;
|
|
|
|
if (s->s_root) {
|
|
if ((flags ^ s->s_flags) & MS_RDONLY) {
|
|
deactivate_locked_super(s);
|
|
error = -EBUSY;
|
|
goto error_bdev;
|
|
}
|
|
|
|
/*
|
|
* s_umount nests inside bd_mutex during
|
|
* __invalidate_device(). blkdev_put() acquires
|
|
* bd_mutex and can't be called under s_umount. Drop
|
|
* s_umount temporarily. This is safe as we're
|
|
* holding an active reference.
|
|
*/
|
|
up_write(&s->s_umount);
|
|
blkdev_put(bdev, mode);
|
|
down_write(&s->s_umount);
|
|
} else {
|
|
char b[BDEVNAME_SIZE];
|
|
|
|
s->s_mode = mode;
|
|
strlcpy(s->s_id, bdevname(bdev, b), sizeof(s->s_id));
|
|
sb_set_blocksize(s, block_size(bdev));
|
|
error = fill_super(s, data, flags & MS_SILENT ? 1 : 0);
|
|
if (error) {
|
|
deactivate_locked_super(s);
|
|
goto error;
|
|
}
|
|
|
|
s->s_flags |= MS_ACTIVE;
|
|
bdev->bd_super = s;
|
|
}
|
|
|
|
return dget(s->s_root);
|
|
|
|
error_s:
|
|
error = PTR_ERR(s);
|
|
error_bdev:
|
|
blkdev_put(bdev, mode);
|
|
error:
|
|
return ERR_PTR(error);
|
|
}
|
|
EXPORT_SYMBOL(mount_bdev);
|
|
|
|
void kill_block_super(struct super_block *sb)
|
|
{
|
|
struct block_device *bdev = sb->s_bdev;
|
|
fmode_t mode = sb->s_mode;
|
|
|
|
bdev->bd_super = NULL;
|
|
generic_shutdown_super(sb);
|
|
sync_blockdev(bdev);
|
|
WARN_ON_ONCE(!(mode & FMODE_EXCL));
|
|
blkdev_put(bdev, mode | FMODE_EXCL);
|
|
}
|
|
|
|
EXPORT_SYMBOL(kill_block_super);
|
|
#endif
|
|
|
|
struct dentry *mount_nodev(struct file_system_type *fs_type,
|
|
int flags, void *data,
|
|
int (*fill_super)(struct super_block *, void *, int))
|
|
{
|
|
int error;
|
|
struct super_block *s = sget(fs_type, NULL, set_anon_super, flags, NULL);
|
|
|
|
if (IS_ERR(s))
|
|
return ERR_CAST(s);
|
|
|
|
error = fill_super(s, data, flags & MS_SILENT ? 1 : 0);
|
|
if (error) {
|
|
deactivate_locked_super(s);
|
|
return ERR_PTR(error);
|
|
}
|
|
s->s_flags |= MS_ACTIVE;
|
|
return dget(s->s_root);
|
|
}
|
|
EXPORT_SYMBOL(mount_nodev);
|
|
|
|
static int compare_single(struct super_block *s, void *p)
|
|
{
|
|
return 1;
|
|
}
|
|
|
|
struct dentry *mount_single(struct file_system_type *fs_type,
|
|
int flags, void *data,
|
|
int (*fill_super)(struct super_block *, void *, int))
|
|
{
|
|
struct super_block *s;
|
|
int error;
|
|
|
|
s = sget(fs_type, compare_single, set_anon_super, flags, NULL);
|
|
if (IS_ERR(s))
|
|
return ERR_CAST(s);
|
|
if (!s->s_root) {
|
|
error = fill_super(s, data, flags & MS_SILENT ? 1 : 0);
|
|
if (error) {
|
|
deactivate_locked_super(s);
|
|
return ERR_PTR(error);
|
|
}
|
|
s->s_flags |= MS_ACTIVE;
|
|
} else {
|
|
do_remount_sb(s, flags, data, 0);
|
|
}
|
|
return dget(s->s_root);
|
|
}
|
|
EXPORT_SYMBOL(mount_single);
|
|
|
|
struct dentry *
|
|
mount_fs(struct file_system_type *type, int flags, const char *name, void *data)
|
|
{
|
|
struct dentry *root;
|
|
struct super_block *sb;
|
|
char *secdata = NULL;
|
|
int error = -ENOMEM;
|
|
|
|
if (data && !(type->fs_flags & FS_BINARY_MOUNTDATA)) {
|
|
secdata = alloc_secdata();
|
|
if (!secdata)
|
|
goto out;
|
|
|
|
error = security_sb_copy_data(data, secdata);
|
|
if (error)
|
|
goto out_free_secdata;
|
|
}
|
|
|
|
root = type->mount(type, flags, name, data);
|
|
if (IS_ERR(root)) {
|
|
error = PTR_ERR(root);
|
|
goto out_free_secdata;
|
|
}
|
|
sb = root->d_sb;
|
|
BUG_ON(!sb);
|
|
WARN_ON(!sb->s_bdi);
|
|
sb->s_flags |= MS_BORN;
|
|
|
|
error = security_sb_kern_mount(sb, flags, secdata);
|
|
if (error)
|
|
goto out_sb;
|
|
|
|
/*
|
|
* filesystems should never set s_maxbytes larger than MAX_LFS_FILESIZE
|
|
* but s_maxbytes was an unsigned long long for many releases. Throw
|
|
* this warning for a little while to try and catch filesystems that
|
|
* violate this rule.
|
|
*/
|
|
WARN((sb->s_maxbytes < 0), "%s set sb->s_maxbytes to "
|
|
"negative value (%lld)\n", type->name, sb->s_maxbytes);
|
|
|
|
up_write(&sb->s_umount);
|
|
free_secdata(secdata);
|
|
return root;
|
|
out_sb:
|
|
dput(root);
|
|
deactivate_locked_super(sb);
|
|
out_free_secdata:
|
|
free_secdata(secdata);
|
|
out:
|
|
return ERR_PTR(error);
|
|
}
|
|
|
|
/*
|
|
* This is an internal function, please use sb_end_{write,pagefault,intwrite}
|
|
* instead.
|
|
*/
|
|
void __sb_end_write(struct super_block *sb, int level)
|
|
{
|
|
percpu_counter_dec(&sb->s_writers.counter[level-1]);
|
|
/*
|
|
* Make sure s_writers are updated before we wake up waiters in
|
|
* freeze_super().
|
|
*/
|
|
smp_mb();
|
|
if (waitqueue_active(&sb->s_writers.wait))
|
|
wake_up(&sb->s_writers.wait);
|
|
rwsem_release(&sb->s_writers.lock_map[level-1], 1, _RET_IP_);
|
|
}
|
|
EXPORT_SYMBOL(__sb_end_write);
|
|
|
|
#ifdef CONFIG_LOCKDEP
|
|
/*
|
|
* We want lockdep to tell us about possible deadlocks with freezing but
|
|
* it's it bit tricky to properly instrument it. Getting a freeze protection
|
|
* works as getting a read lock but there are subtle problems. XFS for example
|
|
* gets freeze protection on internal level twice in some cases, which is OK
|
|
* only because we already hold a freeze protection also on higher level. Due
|
|
* to these cases we have to tell lockdep we are doing trylock when we
|
|
* already hold a freeze protection for a higher freeze level.
|
|
*/
|
|
static void acquire_freeze_lock(struct super_block *sb, int level, bool trylock,
|
|
unsigned long ip)
|
|
{
|
|
int i;
|
|
|
|
if (!trylock) {
|
|
for (i = 0; i < level - 1; i++)
|
|
if (lock_is_held(&sb->s_writers.lock_map[i])) {
|
|
trylock = true;
|
|
break;
|
|
}
|
|
}
|
|
rwsem_acquire_read(&sb->s_writers.lock_map[level-1], 0, trylock, ip);
|
|
}
|
|
#endif
|
|
|
|
/*
|
|
* This is an internal function, please use sb_start_{write,pagefault,intwrite}
|
|
* instead.
|
|
*/
|
|
int __sb_start_write(struct super_block *sb, int level, bool wait)
|
|
{
|
|
retry:
|
|
if (unlikely(sb->s_writers.frozen >= level)) {
|
|
if (!wait)
|
|
return 0;
|
|
wait_event(sb->s_writers.wait_unfrozen,
|
|
sb->s_writers.frozen < level);
|
|
}
|
|
|
|
#ifdef CONFIG_LOCKDEP
|
|
acquire_freeze_lock(sb, level, !wait, _RET_IP_);
|
|
#endif
|
|
percpu_counter_inc(&sb->s_writers.counter[level-1]);
|
|
/*
|
|
* Make sure counter is updated before we check for frozen.
|
|
* freeze_super() first sets frozen and then checks the counter.
|
|
*/
|
|
smp_mb();
|
|
if (unlikely(sb->s_writers.frozen >= level)) {
|
|
__sb_end_write(sb, level);
|
|
goto retry;
|
|
}
|
|
return 1;
|
|
}
|
|
EXPORT_SYMBOL(__sb_start_write);
|
|
|
|
/**
|
|
* sb_wait_write - wait until all writers to given file system finish
|
|
* @sb: the super for which we wait
|
|
* @level: type of writers we wait for (normal vs page fault)
|
|
*
|
|
* This function waits until there are no writers of given type to given file
|
|
* system. Caller of this function should make sure there can be no new writers
|
|
* of type @level before calling this function. Otherwise this function can
|
|
* livelock.
|
|
*/
|
|
static void sb_wait_write(struct super_block *sb, int level)
|
|
{
|
|
s64 writers;
|
|
|
|
/*
|
|
* We just cycle-through lockdep here so that it does not complain
|
|
* about returning with lock to userspace
|
|
*/
|
|
rwsem_acquire(&sb->s_writers.lock_map[level-1], 0, 0, _THIS_IP_);
|
|
rwsem_release(&sb->s_writers.lock_map[level-1], 1, _THIS_IP_);
|
|
|
|
do {
|
|
DEFINE_WAIT(wait);
|
|
|
|
/*
|
|
* We use a barrier in prepare_to_wait() to separate setting
|
|
* of frozen and checking of the counter
|
|
*/
|
|
prepare_to_wait(&sb->s_writers.wait, &wait,
|
|
TASK_UNINTERRUPTIBLE);
|
|
|
|
writers = percpu_counter_sum(&sb->s_writers.counter[level-1]);
|
|
if (writers)
|
|
schedule();
|
|
|
|
finish_wait(&sb->s_writers.wait, &wait);
|
|
} while (writers);
|
|
}
|
|
|
|
/**
|
|
* freeze_super - lock the filesystem and force it into a consistent state
|
|
* @sb: the super to lock
|
|
*
|
|
* Syncs the super to make sure the filesystem is consistent and calls the fs's
|
|
* freeze_fs. Subsequent calls to this without first thawing the fs will return
|
|
* -EBUSY.
|
|
*
|
|
* During this function, sb->s_writers.frozen goes through these values:
|
|
*
|
|
* SB_UNFROZEN: File system is normal, all writes progress as usual.
|
|
*
|
|
* SB_FREEZE_WRITE: The file system is in the process of being frozen. New
|
|
* writes should be blocked, though page faults are still allowed. We wait for
|
|
* all writes to complete and then proceed to the next stage.
|
|
*
|
|
* SB_FREEZE_PAGEFAULT: Freezing continues. Now also page faults are blocked
|
|
* but internal fs threads can still modify the filesystem (although they
|
|
* should not dirty new pages or inodes), writeback can run etc. After waiting
|
|
* for all running page faults we sync the filesystem which will clean all
|
|
* dirty pages and inodes (no new dirty pages or inodes can be created when
|
|
* sync is running).
|
|
*
|
|
* SB_FREEZE_FS: The file system is frozen. Now all internal sources of fs
|
|
* modification are blocked (e.g. XFS preallocation truncation on inode
|
|
* reclaim). This is usually implemented by blocking new transactions for
|
|
* filesystems that have them and need this additional guard. After all
|
|
* internal writers are finished we call ->freeze_fs() to finish filesystem
|
|
* freezing. Then we transition to SB_FREEZE_COMPLETE state. This state is
|
|
* mostly auxiliary for filesystems to verify they do not modify frozen fs.
|
|
*
|
|
* sb->s_writers.frozen is protected by sb->s_umount.
|
|
*/
|
|
int freeze_super(struct super_block *sb)
|
|
{
|
|
int ret;
|
|
|
|
atomic_inc(&sb->s_active);
|
|
down_write(&sb->s_umount);
|
|
if (sb->s_writers.frozen != SB_UNFROZEN) {
|
|
deactivate_locked_super(sb);
|
|
return -EBUSY;
|
|
}
|
|
|
|
if (!(sb->s_flags & MS_BORN)) {
|
|
up_write(&sb->s_umount);
|
|
return 0; /* sic - it's "nothing to do" */
|
|
}
|
|
|
|
if (sb->s_flags & MS_RDONLY) {
|
|
/* Nothing to do really... */
|
|
sb->s_writers.frozen = SB_FREEZE_COMPLETE;
|
|
up_write(&sb->s_umount);
|
|
return 0;
|
|
}
|
|
|
|
/* From now on, no new normal writers can start */
|
|
sb->s_writers.frozen = SB_FREEZE_WRITE;
|
|
smp_wmb();
|
|
|
|
/* Release s_umount to preserve sb_start_write -> s_umount ordering */
|
|
up_write(&sb->s_umount);
|
|
|
|
sb_wait_write(sb, SB_FREEZE_WRITE);
|
|
|
|
/* Now we go and block page faults... */
|
|
down_write(&sb->s_umount);
|
|
sb->s_writers.frozen = SB_FREEZE_PAGEFAULT;
|
|
smp_wmb();
|
|
|
|
sb_wait_write(sb, SB_FREEZE_PAGEFAULT);
|
|
|
|
/* All writers are done so after syncing there won't be dirty data */
|
|
sync_filesystem(sb);
|
|
|
|
/* Now wait for internal filesystem counter */
|
|
sb->s_writers.frozen = SB_FREEZE_FS;
|
|
smp_wmb();
|
|
sb_wait_write(sb, SB_FREEZE_FS);
|
|
|
|
if (sb->s_op->freeze_fs) {
|
|
ret = sb->s_op->freeze_fs(sb);
|
|
if (ret) {
|
|
printk(KERN_ERR
|
|
"VFS:Filesystem freeze failed\n");
|
|
sb->s_writers.frozen = SB_UNFROZEN;
|
|
smp_wmb();
|
|
wake_up(&sb->s_writers.wait_unfrozen);
|
|
deactivate_locked_super(sb);
|
|
return ret;
|
|
}
|
|
}
|
|
/*
|
|
* This is just for debugging purposes so that fs can warn if it
|
|
* sees write activity when frozen is set to SB_FREEZE_COMPLETE.
|
|
*/
|
|
sb->s_writers.frozen = SB_FREEZE_COMPLETE;
|
|
up_write(&sb->s_umount);
|
|
return 0;
|
|
}
|
|
EXPORT_SYMBOL(freeze_super);
|
|
|
|
/**
|
|
* thaw_super -- unlock filesystem
|
|
* @sb: the super to thaw
|
|
*
|
|
* Unlocks the filesystem and marks it writeable again after freeze_super().
|
|
*/
|
|
int thaw_super(struct super_block *sb)
|
|
{
|
|
int error;
|
|
|
|
down_write(&sb->s_umount);
|
|
if (sb->s_writers.frozen == SB_UNFROZEN) {
|
|
up_write(&sb->s_umount);
|
|
return -EINVAL;
|
|
}
|
|
|
|
if (sb->s_flags & MS_RDONLY)
|
|
goto out;
|
|
|
|
if (sb->s_op->unfreeze_fs) {
|
|
error = sb->s_op->unfreeze_fs(sb);
|
|
if (error) {
|
|
printk(KERN_ERR
|
|
"VFS:Filesystem thaw failed\n");
|
|
up_write(&sb->s_umount);
|
|
return error;
|
|
}
|
|
}
|
|
|
|
out:
|
|
sb->s_writers.frozen = SB_UNFROZEN;
|
|
smp_wmb();
|
|
wake_up(&sb->s_writers.wait_unfrozen);
|
|
deactivate_locked_super(sb);
|
|
|
|
return 0;
|
|
}
|
|
EXPORT_SYMBOL(thaw_super);
|