Commit 7994e6f7 authored May 03, 2012 by Jan Kara Committed by Fengguang Wu May 06, 2012

vfs: Move waiting for inode writeback from end_writeback() to evict_inode()



Currently, I_SYNC can never be set when evict_inode() (and thus
end_writeback()) is called because flusher thread holds inode reference while
inode is under writeback. As a result inode_sync_wait() in those places
currently does nothing. However that is going to change and unveils problems
with calling inode_sync_wait() from end_writeback(). Several filesystems call
end_writeback() after they have deleted the inode (btrfs, gfs2, ...) and other
filesystems (ext3, ext4, reiserfs, ...) can deadlock when waiting for I_SYNC
because they call end_writeback() from within a transaction.

To avoid these issues, we move inode_sync_wait() into evict_inode() before
calling ->evict_inode(). That way we preserve the current property that
->evict_inode() and writeback never run in parallel and all filesystems are
safe.

Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Fengguang Wu <fengguang.wu@intel.com>

parent 4f8ad655

fs/inode.c

+2 −1

Original line number	Diff line number	Diff line
		@@ -500,7 +500,6 @@ void end_writeback(struct inode *inode)
		BUG_ON(!list_empty(&inode->i_data.private_list));
		BUG_ON(!(inode->i_state & I_FREEING));
		BUG_ON(inode->i_state & I_CLEAR);
		inode_sync_wait(inode);
		/* don't need i_lock here, no concurrent mods to i_state */
		inode->i_state = I_FREEING \| I_CLEAR;
		}
		@@ -531,6 +530,8 @@ static void evict(struct inode *inode)

		inode_sb_list_del(inode);

		inode_sync_wait(inode);

		if (op->evict_inode) {
		op->evict_inode(inode);
		} else {

Admin message