Re: [PATCH] lock_buffer_wq do lock

Suparna Bhattacharya (suparna@in.ibm.com)
Mon, 16 Jun 2003 19:39:07 +0530


On Mon, Jun 16, 2003 at 02:47:32PM +0100, Hugh Dickins wrote:
> I've twice got fs/buffer.c:2668 submit_bh BUG_ON(!buffer_locked(bh)):
> when called from sync_dirty_buffer which clearly does the lock_buffer.
> My suspicion falls on lock_buffer_wq (whereas __lock_page_wq looks OK).
>
> I'm leaving a test running,
> can't judge until tomorrow whether this is indeed the fix to that.
>
> Hugh
>
> --- 2.5.71-mm1/include/linux/buffer_head.h Sun Jun 15 12:36:11 2003
> +++ linux/include/linux/buffer_head.h Mon Jun 16 14:13:25 2003
> @@ -291,9 +291,11 @@
>
> static inline int lock_buffer_wq(struct buffer_head *bh, wait_queue_t *wait)
> {
> - if (test_set_buffer_locked(bh))
> - return __wait_on_buffer_wq(bh, wait);
> -
> + while (test_set_buffer_locked(bh)) {
> + int ret = __wait_on_buffer_wq(bh, wait);
> + if (ret)
> + return ret;
> + }
> return 0;
> }

You are right - this should be a while loop mirroring what
lock_buffer does.

Actually, I probably ought to just avoid the dual paths,
and make lock_buffer a wrapper for lock_buffer_wq -- less
chances of divergence between the two.

Regards
Suparna

-- 
Suparna Bhattacharya (suparna@in.ibm.com)
Linux Technology Center
IBM Software Labs, India

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