linux-ext4 - Re: [PATCH] jbd jbd2: fix dio write returningEIOwhentry_to_release

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Date:	Wed, 06 Aug 2008 17:39:28 +0900
From:	Hisashi Hifumi <hifumi.hisashi@....ntt.co.jp>
To:	Mingming Cao <cmm@...ibm.com>, Chris Mason <chris.mason@...cle.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>, jack@...e.cz,
	linux-ext4@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH] jbd jbd2: fix dio write
  returningEIOwhentry_to_release_page fails


>I modified my patch.
>I do not change Checking b_count in a loop, but introduce 
>set_current_state(TASK_UNINTERRUPTIBLE) to mitigate the loop. I think this can 
>lead to avoid busy loop.
>I used the same approach of do_sync_read()->wait_on_retry_sync_kiocb or 
>some drivers(qla2xxx).
>
>Signed-off-by: Hisashi Hifumi <hifumi.hisashi@....ntt.co.jp>
>
>diff -Nrup linux-2.6.27-rc1.org/fs/jbd/transaction.c 
>linux-2.6.27-rc1.jbdfix/fs/jbd/transaction.c
>--- linux-2.6.27-rc1.org/fs/jbd/transaction.c	2008-07-29 19:28:47.000000000 +0900
>+++ linux-2.6.27-rc1.jbdfix/fs/jbd/transaction.c	2008-08-06 
>13:35:37.000000000 +0900
>@@ -1764,6 +1764,15 @@ int journal_try_to_free_buffers(journal_
> 	*/
> 	if (ret == 0 && (gfp_mask & __GFP_WAIT) && (gfp_mask & __GFP_FS)) {
> 		journal_wait_for_transaction_sync_data(journal);
>+
>+		bh = head;
>+		do {
>+			while (atomic_read(&bh->b_count)) {
>+				set_current_state(TASK_UNINTERRUPTIBLE);
>+				schedule();
>+				__set_current_state(TASK_RUNNING);
>+			}
>+		} while ((bh = bh->b_this_page) != head);
> 		ret = try_to_free_buffers(page);
> 	}

Sorry, the thread entering this loop sleeps infinitely.
We should add some wait queue and implement wait/wakeup code.

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