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Commit 580be083 authored by Jan Kara's avatar Jan Kara Committed by Linus Torvalds
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fs: make sure data stored into inode is properly seen before unlocking new inode 



In theory it could happen that on one CPU we initialize a new inode but
clearing of I_NEW | I_LOCK gets reordered before some of the
initialization.  Thus on another CPU we return not fully uptodate inode
from iget_locked().

This seems to fix a corruption issue on ext3 mounted over NFS.

[akpm@linux-foundation.org: add some commentary]
Signed-off-by: default avatarJan Kara <jack@suse.cz>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: <stable@kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 5be46165

fs/inode.c

+8 −6
Original line number Diff line number Diff line
@@ -695,13 +695,15 @@ void unlock_new_inode(struct inode *inode) 
	}

#endif

	/*

	 * This is special!  We do not need the spinlock

	 * when clearing I_LOCK, because we're guaranteed

	 * that nobody else tries to do anything about the

	 * state of the inode when it is locked, as we

	 * just created it (so there can be no old holders

	 * that haven't tested I_LOCK).

	 * This is special!  We do not need the spinlock when clearing I_LOCK,

	 * because we're guaranteed that nobody else tries to do anything about

	 * the state of the inode when it is locked, as we just created it (so

	 * there can be no old holders that haven't tested I_LOCK).

	 * However we must emit the memory barrier so that other CPUs reliably

	 * see the clearing of I_LOCK after the other inode initialisation has

	 * completed.

	 */

	smp_mb();

	WARN_ON((inode->i_state & (I_LOCK|I_NEW)) != (I_LOCK|I_NEW));

	inode->i_state &= ~(I_LOCK|I_NEW);

	wake_up_inode(inode);