Re: [PATCH] VFS bugfix: two read_inode() calles withoutclear_inode() call between

[Miklos Szeredi]

> That comment isn't true any more. Look at what __wait_on_freeing_inode()
> actually does, and observe the fact that all its callers actually loop
> and start again after calling it. 
> 
> The current implementation of __wait_on_freeing_inode() waits until it
> _might_ have changed, not until it _has_ changed. That's why it's OK for
> it just to be a yield() or a wait on a bit_waitqueue.
> 
> I'm not convinced I _like_ that implementation, mind you -- it's changed
> since I last looked at it. But I don't see that there's anything
> strictly broken about it.

Using yield() to wait for a precisely defined event (clear_inode()
finishing) doesn't seem like a very good idea.  Especially, since
Artem's patch will probably make it trigger more often.

How about this (totally untested) patch?  Even if I_LOCK is not set
initially, wake_up_inode() should do the right thing and wake up the
waiting task after clear_inode().  It shouldn't cause spurious
wakeups, since there should be no other reference to the inode.

Miklos

--- inode.c~	2005-05-02 11:24:49.000000000 +0200
+++ inode.c	2005-05-05 18:12:57.000000000 +0200
@@ -1264,18 +1264,6 @@ static void __wait_on_freeing_inode(stru
 {
 	wait_queue_head_t *wq;
 	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);
 	prepare_to_wait(wq, &wait.wait, TASK_UNINTERRUPTIBLE);
 	spin_unlock(&inode_lock);
-
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