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4ffc844425
In here, I think the following order is more cache-friendly. Signed-off-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
693 lines
20 KiB
C
693 lines
20 KiB
C
/*
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* fs/fs-writeback.c
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*
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* Copyright (C) 2002, Linus Torvalds.
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*
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* Contains all the functions related to writing back and waiting
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* upon dirty inodes against superblocks, and writing back dirty
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* pages against inodes. ie: data writeback. Writeout of the
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* inode itself is not handled here.
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*
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* 10Apr2002 akpm@zip.com.au
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* Split out of fs/inode.c
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* Additions for address_space-based writeback
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*/
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#include <linux/kernel.h>
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#include <linux/spinlock.h>
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#include <linux/sched.h>
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#include <linux/fs.h>
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#include <linux/mm.h>
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#include <linux/writeback.h>
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#include <linux/blkdev.h>
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#include <linux/backing-dev.h>
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#include <linux/buffer_head.h>
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extern struct super_block *blockdev_superblock;
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/**
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* __mark_inode_dirty - internal function
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* @inode: inode to mark
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* @flags: what kind of dirty (i.e. I_DIRTY_SYNC)
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* Mark an inode as dirty. Callers should use mark_inode_dirty or
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* mark_inode_dirty_sync.
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*
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* Put the inode on the super block's dirty list.
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*
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* CAREFUL! We mark it dirty unconditionally, but move it onto the
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* dirty list only if it is hashed or if it refers to a blockdev.
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* If it was not hashed, it will never be added to the dirty list
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* even if it is later hashed, as it will have been marked dirty already.
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*
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* In short, make sure you hash any inodes _before_ you start marking
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* them dirty.
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*
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* This function *must* be atomic for the I_DIRTY_PAGES case -
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* set_page_dirty() is called under spinlock in several places.
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*
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* Note that for blockdevs, inode->dirtied_when represents the dirtying time of
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* the block-special inode (/dev/hda1) itself. And the ->dirtied_when field of
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* the kernel-internal blockdev inode represents the dirtying time of the
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* blockdev's pages. This is why for I_DIRTY_PAGES we always use
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* page->mapping->host, so the page-dirtying time is recorded in the internal
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* blockdev inode.
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*/
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void __mark_inode_dirty(struct inode *inode, int flags)
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{
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struct super_block *sb = inode->i_sb;
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/*
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* Don't do this for I_DIRTY_PAGES - that doesn't actually
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* dirty the inode itself
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*/
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if (flags & (I_DIRTY_SYNC | I_DIRTY_DATASYNC)) {
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if (sb->s_op->dirty_inode)
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sb->s_op->dirty_inode(inode);
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}
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/*
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* make sure that changes are seen by all cpus before we test i_state
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* -- mikulas
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*/
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smp_mb();
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/* avoid the locking if we can */
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if ((inode->i_state & flags) == flags)
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return;
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if (unlikely(block_dump)) {
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struct dentry *dentry = NULL;
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const char *name = "?";
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if (!list_empty(&inode->i_dentry)) {
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dentry = list_entry(inode->i_dentry.next,
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struct dentry, d_alias);
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if (dentry && dentry->d_name.name)
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name = (const char *) dentry->d_name.name;
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}
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if (inode->i_ino || strcmp(inode->i_sb->s_id, "bdev"))
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printk(KERN_DEBUG
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"%s(%d): dirtied inode %lu (%s) on %s\n",
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current->comm, current->pid, inode->i_ino,
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name, inode->i_sb->s_id);
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}
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spin_lock(&inode_lock);
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if ((inode->i_state & flags) != flags) {
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const int was_dirty = inode->i_state & I_DIRTY;
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inode->i_state |= flags;
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/*
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* If the inode is locked, just update its dirty state.
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* The unlocker will place the inode on the appropriate
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* superblock list, based upon its state.
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*/
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if (inode->i_state & I_LOCK)
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goto out;
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/*
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* Only add valid (hashed) inodes to the superblock's
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* dirty list. Add blockdev inodes as well.
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*/
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if (!S_ISBLK(inode->i_mode)) {
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if (hlist_unhashed(&inode->i_hash))
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goto out;
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}
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if (inode->i_state & (I_FREEING|I_CLEAR))
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goto out;
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/*
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* If the inode was already on s_dirty or s_io, don't
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* reposition it (that would break s_dirty time-ordering).
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*/
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if (!was_dirty) {
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inode->dirtied_when = jiffies;
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list_move(&inode->i_list, &sb->s_dirty);
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}
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}
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out:
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spin_unlock(&inode_lock);
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}
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EXPORT_SYMBOL(__mark_inode_dirty);
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static int write_inode(struct inode *inode, int sync)
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{
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if (inode->i_sb->s_op->write_inode && !is_bad_inode(inode))
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return inode->i_sb->s_op->write_inode(inode, sync);
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return 0;
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}
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/*
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* Write a single inode's dirty pages and inode data out to disk.
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* If `wait' is set, wait on the writeout.
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*
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* The whole writeout design is quite complex and fragile. We want to avoid
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* starvation of particular inodes when others are being redirtied, prevent
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* livelocks, etc.
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*
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* Called under inode_lock.
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*/
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static int
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__sync_single_inode(struct inode *inode, struct writeback_control *wbc)
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{
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unsigned dirty;
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struct address_space *mapping = inode->i_mapping;
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struct super_block *sb = inode->i_sb;
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int wait = wbc->sync_mode == WB_SYNC_ALL;
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int ret;
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BUG_ON(inode->i_state & I_LOCK);
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/* Set I_LOCK, reset I_DIRTY */
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dirty = inode->i_state & I_DIRTY;
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inode->i_state |= I_LOCK;
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inode->i_state &= ~I_DIRTY;
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spin_unlock(&inode_lock);
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ret = do_writepages(mapping, wbc);
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/* Don't write the inode if only I_DIRTY_PAGES was set */
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if (dirty & (I_DIRTY_SYNC | I_DIRTY_DATASYNC)) {
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int err = write_inode(inode, wait);
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if (ret == 0)
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ret = err;
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}
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if (wait) {
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int err = filemap_fdatawait(mapping);
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if (ret == 0)
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ret = err;
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}
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spin_lock(&inode_lock);
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inode->i_state &= ~I_LOCK;
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if (!(inode->i_state & I_FREEING)) {
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if (!(inode->i_state & I_DIRTY) &&
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mapping_tagged(mapping, PAGECACHE_TAG_DIRTY)) {
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/*
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* We didn't write back all the pages. nfs_writepages()
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* sometimes bales out without doing anything. Redirty
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* the inode. It is still on sb->s_io.
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*/
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if (wbc->for_kupdate) {
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/*
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* For the kupdate function we leave the inode
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* at the head of sb_dirty so it will get more
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* writeout as soon as the queue becomes
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* uncongested.
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*/
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inode->i_state |= I_DIRTY_PAGES;
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list_move_tail(&inode->i_list, &sb->s_dirty);
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} else {
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/*
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* Otherwise fully redirty the inode so that
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* other inodes on this superblock will get some
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* writeout. Otherwise heavy writing to one
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* file would indefinitely suspend writeout of
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* all the other files.
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*/
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inode->i_state |= I_DIRTY_PAGES;
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inode->dirtied_when = jiffies;
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list_move(&inode->i_list, &sb->s_dirty);
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}
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} else if (inode->i_state & I_DIRTY) {
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/*
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* Someone redirtied the inode while were writing back
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* the pages.
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*/
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list_move(&inode->i_list, &sb->s_dirty);
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} else if (atomic_read(&inode->i_count)) {
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/*
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* The inode is clean, inuse
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*/
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list_move(&inode->i_list, &inode_in_use);
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} else {
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/*
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* The inode is clean, unused
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*/
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list_move(&inode->i_list, &inode_unused);
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}
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}
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wake_up_inode(inode);
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return ret;
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}
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/*
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* Write out an inode's dirty pages. Called under inode_lock. Either the
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* caller has ref on the inode (either via __iget or via syscall against an fd)
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* or the inode has I_WILL_FREE set (via generic_forget_inode)
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*/
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static int
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__writeback_single_inode(struct inode *inode, struct writeback_control *wbc)
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{
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wait_queue_head_t *wqh;
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if (!atomic_read(&inode->i_count))
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WARN_ON(!(inode->i_state & (I_WILL_FREE|I_FREEING)));
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else
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WARN_ON(inode->i_state & I_WILL_FREE);
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if ((wbc->sync_mode != WB_SYNC_ALL) && (inode->i_state & I_LOCK)) {
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list_move(&inode->i_list, &inode->i_sb->s_dirty);
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return 0;
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}
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/*
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* It's a data-integrity sync. We must wait.
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*/
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if (inode->i_state & I_LOCK) {
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DEFINE_WAIT_BIT(wq, &inode->i_state, __I_LOCK);
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wqh = bit_waitqueue(&inode->i_state, __I_LOCK);
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do {
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spin_unlock(&inode_lock);
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__wait_on_bit(wqh, &wq, inode_wait,
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TASK_UNINTERRUPTIBLE);
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spin_lock(&inode_lock);
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} while (inode->i_state & I_LOCK);
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}
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return __sync_single_inode(inode, wbc);
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}
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/*
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* Write out a superblock's list of dirty inodes. A wait will be performed
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* upon no inodes, all inodes or the final one, depending upon sync_mode.
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*
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* If older_than_this is non-NULL, then only write out inodes which
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* had their first dirtying at a time earlier than *older_than_this.
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*
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* If we're a pdlfush thread, then implement pdflush collision avoidance
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* against the entire list.
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*
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* WB_SYNC_HOLD is a hack for sys_sync(): reattach the inode to sb->s_dirty so
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* that it can be located for waiting on in __writeback_single_inode().
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*
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* Called under inode_lock.
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*
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* If `bdi' is non-zero then we're being asked to writeback a specific queue.
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* This function assumes that the blockdev superblock's inodes are backed by
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* a variety of queues, so all inodes are searched. For other superblocks,
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* assume that all inodes are backed by the same queue.
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*
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* FIXME: this linear search could get expensive with many fileystems. But
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* how to fix? We need to go from an address_space to all inodes which share
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* a queue with that address_space. (Easy: have a global "dirty superblocks"
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* list).
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*
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* The inodes to be written are parked on sb->s_io. They are moved back onto
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* sb->s_dirty as they are selected for writing. This way, none can be missed
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* on the writer throttling path, and we get decent balancing between many
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* throttled threads: we don't want them all piling up on __wait_on_inode.
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*/
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static void
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sync_sb_inodes(struct super_block *sb, struct writeback_control *wbc)
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{
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const unsigned long start = jiffies; /* livelock avoidance */
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if (!wbc->for_kupdate || list_empty(&sb->s_io))
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list_splice_init(&sb->s_dirty, &sb->s_io);
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while (!list_empty(&sb->s_io)) {
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struct inode *inode = list_entry(sb->s_io.prev,
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struct inode, i_list);
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struct address_space *mapping = inode->i_mapping;
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struct backing_dev_info *bdi = mapping->backing_dev_info;
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long pages_skipped;
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if (!bdi_cap_writeback_dirty(bdi)) {
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list_move(&inode->i_list, &sb->s_dirty);
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if (sb == blockdev_superblock) {
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/*
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* Dirty memory-backed blockdev: the ramdisk
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* driver does this. Skip just this inode
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*/
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continue;
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}
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/*
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* Dirty memory-backed inode against a filesystem other
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* than the kernel-internal bdev filesystem. Skip the
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* entire superblock.
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*/
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break;
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}
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if (wbc->nonblocking && bdi_write_congested(bdi)) {
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wbc->encountered_congestion = 1;
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if (sb != blockdev_superblock)
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break; /* Skip a congested fs */
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list_move(&inode->i_list, &sb->s_dirty);
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continue; /* Skip a congested blockdev */
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}
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if (wbc->bdi && bdi != wbc->bdi) {
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if (sb != blockdev_superblock)
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break; /* fs has the wrong queue */
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list_move(&inode->i_list, &sb->s_dirty);
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continue; /* blockdev has wrong queue */
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}
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/* Was this inode dirtied after sync_sb_inodes was called? */
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if (time_after(inode->dirtied_when, start))
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break;
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/* Was this inode dirtied too recently? */
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if (wbc->older_than_this && time_after(inode->dirtied_when,
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*wbc->older_than_this))
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break;
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/* Is another pdflush already flushing this queue? */
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if (current_is_pdflush() && !writeback_acquire(bdi))
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break;
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BUG_ON(inode->i_state & I_FREEING);
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__iget(inode);
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pages_skipped = wbc->pages_skipped;
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__writeback_single_inode(inode, wbc);
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if (wbc->sync_mode == WB_SYNC_HOLD) {
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inode->dirtied_when = jiffies;
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list_move(&inode->i_list, &sb->s_dirty);
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}
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if (current_is_pdflush())
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writeback_release(bdi);
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if (wbc->pages_skipped != pages_skipped) {
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/*
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* writeback is not making progress due to locked
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* buffers. Skip this inode for now.
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*/
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list_move(&inode->i_list, &sb->s_dirty);
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}
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spin_unlock(&inode_lock);
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iput(inode);
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cond_resched();
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spin_lock(&inode_lock);
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if (wbc->nr_to_write <= 0)
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break;
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}
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return; /* Leave any unwritten inodes on s_io */
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}
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/*
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* Start writeback of dirty pagecache data against all unlocked inodes.
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*
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* Note:
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* We don't need to grab a reference to superblock here. If it has non-empty
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* ->s_dirty it's hadn't been killed yet and kill_super() won't proceed
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* past sync_inodes_sb() until both the ->s_dirty and ->s_io lists are
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* empty. Since __sync_single_inode() regains inode_lock before it finally moves
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* inode from superblock lists we are OK.
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*
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* If `older_than_this' is non-zero then only flush inodes which have a
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* flushtime older than *older_than_this.
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*
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* If `bdi' is non-zero then we will scan the first inode against each
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* superblock until we find the matching ones. One group will be the dirty
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* inodes against a filesystem. Then when we hit the dummy blockdev superblock,
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* sync_sb_inodes will seekout the blockdev which matches `bdi'. Maybe not
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* super-efficient but we're about to do a ton of I/O...
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*/
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void
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writeback_inodes(struct writeback_control *wbc)
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{
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struct super_block *sb;
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might_sleep();
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spin_lock(&sb_lock);
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restart:
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sb = sb_entry(super_blocks.prev);
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for (; sb != sb_entry(&super_blocks); sb = sb_entry(sb->s_list.prev)) {
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if (!list_empty(&sb->s_dirty) || !list_empty(&sb->s_io)) {
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/* we're making our own get_super here */
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sb->s_count++;
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spin_unlock(&sb_lock);
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/*
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* If we can't get the readlock, there's no sense in
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* waiting around, most of the time the FS is going to
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* be unmounted by the time it is released.
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*/
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if (down_read_trylock(&sb->s_umount)) {
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if (sb->s_root) {
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spin_lock(&inode_lock);
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sync_sb_inodes(sb, wbc);
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spin_unlock(&inode_lock);
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}
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up_read(&sb->s_umount);
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}
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spin_lock(&sb_lock);
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if (__put_super_and_need_restart(sb))
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goto restart;
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}
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if (wbc->nr_to_write <= 0)
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break;
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}
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spin_unlock(&sb_lock);
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}
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/*
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* writeback and wait upon the filesystem's dirty inodes. The caller will
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* do this in two passes - one to write, and one to wait. WB_SYNC_HOLD is
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* used to park the written inodes on sb->s_dirty for the wait pass.
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*
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* A finite limit is set on the number of pages which will be written.
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* To prevent infinite livelock of sys_sync().
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*
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* We add in the number of potentially dirty inodes, because each inode write
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* can dirty pagecache in the underlying blockdev.
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*/
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void sync_inodes_sb(struct super_block *sb, int wait)
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{
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struct writeback_control wbc = {
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.sync_mode = wait ? WB_SYNC_ALL : WB_SYNC_HOLD,
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};
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unsigned long nr_dirty = read_page_state(nr_dirty);
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unsigned long nr_unstable = read_page_state(nr_unstable);
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wbc.nr_to_write = nr_dirty + nr_unstable +
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(inodes_stat.nr_inodes - inodes_stat.nr_unused) +
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nr_dirty + nr_unstable;
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wbc.nr_to_write += wbc.nr_to_write / 2; /* Bit more for luck */
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spin_lock(&inode_lock);
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sync_sb_inodes(sb, &wbc);
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spin_unlock(&inode_lock);
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}
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/*
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* Rather lame livelock avoidance.
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*/
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static void set_sb_syncing(int val)
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{
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struct super_block *sb;
|
|
spin_lock(&sb_lock);
|
|
sb = sb_entry(super_blocks.prev);
|
|
for (; sb != sb_entry(&super_blocks); sb = sb_entry(sb->s_list.prev)) {
|
|
sb->s_syncing = val;
|
|
}
|
|
spin_unlock(&sb_lock);
|
|
}
|
|
|
|
/**
|
|
* sync_inodes - writes all inodes to disk
|
|
* @wait: wait for completion
|
|
*
|
|
* sync_inodes() goes through each super block's dirty inode list, writes the
|
|
* inodes out, waits on the writeout and puts the inodes back on the normal
|
|
* list.
|
|
*
|
|
* This is for sys_sync(). fsync_dev() uses the same algorithm. The subtle
|
|
* part of the sync functions is that the blockdev "superblock" is processed
|
|
* last. This is because the write_inode() function of a typical fs will
|
|
* perform no I/O, but will mark buffers in the blockdev mapping as dirty.
|
|
* What we want to do is to perform all that dirtying first, and then write
|
|
* back all those inode blocks via the blockdev mapping in one sweep. So the
|
|
* additional (somewhat redundant) sync_blockdev() calls here are to make
|
|
* sure that really happens. Because if we call sync_inodes_sb(wait=1) with
|
|
* outstanding dirty inodes, the writeback goes block-at-a-time within the
|
|
* filesystem's write_inode(). This is extremely slow.
|
|
*/
|
|
static void __sync_inodes(int wait)
|
|
{
|
|
struct super_block *sb;
|
|
|
|
spin_lock(&sb_lock);
|
|
restart:
|
|
list_for_each_entry(sb, &super_blocks, s_list) {
|
|
if (sb->s_syncing)
|
|
continue;
|
|
sb->s_syncing = 1;
|
|
sb->s_count++;
|
|
spin_unlock(&sb_lock);
|
|
down_read(&sb->s_umount);
|
|
if (sb->s_root) {
|
|
sync_inodes_sb(sb, wait);
|
|
sync_blockdev(sb->s_bdev);
|
|
}
|
|
up_read(&sb->s_umount);
|
|
spin_lock(&sb_lock);
|
|
if (__put_super_and_need_restart(sb))
|
|
goto restart;
|
|
}
|
|
spin_unlock(&sb_lock);
|
|
}
|
|
|
|
void sync_inodes(int wait)
|
|
{
|
|
set_sb_syncing(0);
|
|
__sync_inodes(0);
|
|
|
|
if (wait) {
|
|
set_sb_syncing(0);
|
|
__sync_inodes(1);
|
|
}
|
|
}
|
|
|
|
/**
|
|
* write_inode_now - write an inode to disk
|
|
* @inode: inode to write to disk
|
|
* @sync: whether the write should be synchronous or not
|
|
*
|
|
* This function commits an inode to disk immediately if it is dirty. This is
|
|
* primarily needed by knfsd.
|
|
*
|
|
* The caller must either have a ref on the inode or must have set I_WILL_FREE.
|
|
*/
|
|
int write_inode_now(struct inode *inode, int sync)
|
|
{
|
|
int ret;
|
|
struct writeback_control wbc = {
|
|
.nr_to_write = LONG_MAX,
|
|
.sync_mode = WB_SYNC_ALL,
|
|
};
|
|
|
|
if (!mapping_cap_writeback_dirty(inode->i_mapping))
|
|
wbc.nr_to_write = 0;
|
|
|
|
might_sleep();
|
|
spin_lock(&inode_lock);
|
|
ret = __writeback_single_inode(inode, &wbc);
|
|
spin_unlock(&inode_lock);
|
|
if (sync)
|
|
wait_on_inode(inode);
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL(write_inode_now);
|
|
|
|
/**
|
|
* sync_inode - write an inode and its pages to disk.
|
|
* @inode: the inode to sync
|
|
* @wbc: controls the writeback mode
|
|
*
|
|
* sync_inode() will write an inode and its pages to disk. It will also
|
|
* correctly update the inode on its superblock's dirty inode lists and will
|
|
* update inode->i_state.
|
|
*
|
|
* The caller must have a ref on the inode.
|
|
*/
|
|
int sync_inode(struct inode *inode, struct writeback_control *wbc)
|
|
{
|
|
int ret;
|
|
|
|
spin_lock(&inode_lock);
|
|
ret = __writeback_single_inode(inode, wbc);
|
|
spin_unlock(&inode_lock);
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL(sync_inode);
|
|
|
|
/**
|
|
* generic_osync_inode - flush all dirty data for a given inode to disk
|
|
* @inode: inode to write
|
|
* @mapping: the address_space that should be flushed
|
|
* @what: what to write and wait upon
|
|
*
|
|
* This can be called by file_write functions for files which have the
|
|
* O_SYNC flag set, to flush dirty writes to disk.
|
|
*
|
|
* @what is a bitmask, specifying which part of the inode's data should be
|
|
* written and waited upon.
|
|
*
|
|
* OSYNC_DATA: i_mapping's dirty data
|
|
* OSYNC_METADATA: the buffers at i_mapping->private_list
|
|
* OSYNC_INODE: the inode itself
|
|
*/
|
|
|
|
int generic_osync_inode(struct inode *inode, struct address_space *mapping, int what)
|
|
{
|
|
int err = 0;
|
|
int need_write_inode_now = 0;
|
|
int err2;
|
|
|
|
current->flags |= PF_SYNCWRITE;
|
|
if (what & OSYNC_DATA)
|
|
err = filemap_fdatawrite(mapping);
|
|
if (what & (OSYNC_METADATA|OSYNC_DATA)) {
|
|
err2 = sync_mapping_buffers(mapping);
|
|
if (!err)
|
|
err = err2;
|
|
}
|
|
if (what & OSYNC_DATA) {
|
|
err2 = filemap_fdatawait(mapping);
|
|
if (!err)
|
|
err = err2;
|
|
}
|
|
current->flags &= ~PF_SYNCWRITE;
|
|
|
|
spin_lock(&inode_lock);
|
|
if ((inode->i_state & I_DIRTY) &&
|
|
((what & OSYNC_INODE) || (inode->i_state & I_DIRTY_DATASYNC)))
|
|
need_write_inode_now = 1;
|
|
spin_unlock(&inode_lock);
|
|
|
|
if (need_write_inode_now) {
|
|
err2 = write_inode_now(inode, 1);
|
|
if (!err)
|
|
err = err2;
|
|
}
|
|
else
|
|
wait_on_inode(inode);
|
|
|
|
return err;
|
|
}
|
|
|
|
EXPORT_SYMBOL(generic_osync_inode);
|
|
|
|
/**
|
|
* writeback_acquire: attempt to get exclusive writeback access to a device
|
|
* @bdi: the device's backing_dev_info structure
|
|
*
|
|
* It is a waste of resources to have more than one pdflush thread blocked on
|
|
* a single request queue. Exclusion at the request_queue level is obtained
|
|
* via a flag in the request_queue's backing_dev_info.state.
|
|
*
|
|
* Non-request_queue-backed address_spaces will share default_backing_dev_info,
|
|
* unless they implement their own. Which is somewhat inefficient, as this
|
|
* may prevent concurrent writeback against multiple devices.
|
|
*/
|
|
int writeback_acquire(struct backing_dev_info *bdi)
|
|
{
|
|
return !test_and_set_bit(BDI_pdflush, &bdi->state);
|
|
}
|
|
|
|
/**
|
|
* writeback_in_progress: determine whether there is writeback in progress
|
|
* @bdi: the device's backing_dev_info structure.
|
|
*
|
|
* Determine whether there is writeback in progress against a backing device.
|
|
*/
|
|
int writeback_in_progress(struct backing_dev_info *bdi)
|
|
{
|
|
return test_bit(BDI_pdflush, &bdi->state);
|
|
}
|
|
|
|
/**
|
|
* writeback_release: relinquish exclusive writeback access against a device.
|
|
* @bdi: the device's backing_dev_info structure
|
|
*/
|
|
void writeback_release(struct backing_dev_info *bdi)
|
|
{
|
|
BUG_ON(!writeback_in_progress(bdi));
|
|
clear_bit(BDI_pdflush, &bdi->state);
|
|
}
|