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Commit 168a9fd6 authored by Miklos Szeredi's avatar Miklos Szeredi Committed by Linus Torvalds
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[PATCH] __wait_on_freeing_inode fix 



This patch fixes queer behavior in __wait_on_freeing_inode().

If I_LOCK was not set it called yield(), effectively busy waiting for the
removal of the inode from the hash.  This change was introduced within
"[PATCH] eliminate inode waitqueue hashtable" Changeset 1.1938.166.16 last
october by wli.

The solution is to restore the old behavior, of unconditionally waiting on
the waitqueue.  It doesn't matter if I_LOCK is not set initally, the task
will go to sleep, and wake up when wake_up_inode() is called from
generic_delete_inode() after removing the inode from the hash chain.

Comment is also updated to better reflect current behavior.

This condition is very hard to trigger normally (simultaneous clear_inode()
with iget()) so probably only heavy stress testing can reveal any change of
behavior.

Signed-off-by: default avatarMiklos Szeredi <miklos@szeredi.hu>
Acked-by: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 3b6bfcdb

fs/inode.c

+9 −17
Original line number Original line Diff line number Diff line
@@ -1244,29 +1244,21 @@ int inode_wait(void *word) 
}

}





/*

/*

 * If we try to find an inode in the inode hash while it is being deleted, we

 * If we try to find an inode in the inode hash while it is being

 * have to wait until the filesystem completes its deletion before reporting

 * deleted, we have to wait until the filesystem completes its

 * that it isn't found.  This is because iget will immediately call

 * deletion before reporting that it isn't found.  This function waits

 * ->read_inode, and we want to be sure that evidence of the deletion is found

 * until the deletion _might_ have completed.  Callers are responsible

 * by ->read_inode.

 * to recheck inode state.

 *

 * It doesn't matter if I_LOCK is not set initially, a call to

 * wake_up_inode() after removing from the hash list will DTRT.

 *

 * This is called with inode_lock held.

 * This is called with inode_lock held.

 */

 */

static void __wait_on_freeing_inode(struct inode *inode)

static void __wait_on_freeing_inode(struct inode *inode)

{

{

	wait_queue_head_t *wq;

	wait_queue_head_t *wq;

	DEFINE_WAIT_BIT(wait, &inode->i_state, __I_LOCK);

	DEFINE_WAIT_BIT(wait, &inode->i_state, __I_LOCK);



	/*

	 * I_FREEING and I_CLEAR are cleared in process context under

	 * inode_lock, so we have to give the tasks who would clear them

	 * a chance to run and acquire inode_lock.

	 */

	if (!(inode->i_state & I_LOCK)) {

		spin_unlock(&inode_lock);

		yield();

		spin_lock(&inode_lock);

		return;

	}

	wq = bit_waitqueue(&inode->i_state, __I_LOCK);

	wq = bit_waitqueue(&inode->i_state, __I_LOCK);

	prepare_to_wait(wq, &wait.wait, TASK_UNINTERRUPTIBLE);

	prepare_to_wait(wq, &wait.wait, TASK_UNINTERRUPTIBLE);

	spin_unlock(&inode_lock);

	spin_unlock(&inode_lock);