linux-ext4 - [BUG][PATCH 2/4] ext4: fix a cause of __schedule_bug via blkdev

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Message-Id: <20081202200912.493b2e8c.toshi.okajima@jp.fujitsu.com>
Date:	Tue, 2 Dec 2008 20:09:12 +0900
From:	Toshiyuki Okajima <toshi.okajima@...fujitsu.com>
To:	aneesh.kumar@...ux.vnet.ibm.com, balbir@...ux.vnet.ibm.com,
	tytso@....edu
Cc:	linux-ext4@...r.kernel.org
Subject: [BUG][PATCH 2/4] ext4: fix a cause of __schedule_bug via
 blkdev_releasepage

ext4: fix a cause of __schedule_bug via blkdev_releasepage
From: Toshiyuki Okajima <toshi.okajima@...fujitsu.com>

A cause of this problem is calling jbd2_log_wait_commit() on 
jbd2_journal_try_to_free_buffers() with a read-lock via blkdev_releasepage(). 
This logic is for uncommitted data buffers. And a read/write-lock is required 
for a client usage of blkdev_releasepage.

By the way, we want to release only metadata buffers on ext4_release_metadata().
Because a page which binds to blkdev is used as metadata for ext4.

Therefore we don't need to wait for a commit on 
jbd2_journal_try_to_free_buffers() via ext4_release_matadata().
As a result, we add a jbd2_journal_try_to_free_metadata_buffers() almost same 
as jbd2_journal_try_to_free_buffers() except not calling jbd2_log_wait_commit().
So, we change jbd2_journal_try_to_free_buffers() with 
jbd2_journal_try_to_free_metadata_buffers().

This issue was reported by Aneesh Kumar K.V.
http://marc.info/?l=linux-ext4&m=122814568309893&w=2

Reported-by: "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
Signed-off-by: Toshiyuki Okajima <toshi.okajima@...fujitsu.com>
Cc: Balbir Singh <balbir@...ux.vnet.ibm.com> 
Cc: "Theodore Ts'o" <tytso@....edu>
--
 fs/ext4/inode.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff -Nurp linux-2.6.28-rc6/fs/ext4/inode.c linux-2.6.28-rc6.2/fs/ext4/inode.c
--- linux-2.6.28-rc6/fs/ext4/inode.c	2008-12-02 09:32:27.000000000 +0900
+++ linux-2.6.28-rc6.2/fs/ext4/inode.c	2008-12-02 09:52:46.000000000 +0900
@@ -3018,7 +3018,7 @@ int ext4_release_metadata(void *client, 
 	BUG_ON(EXT4_SB(sb) == NULL);
 	journal = EXT4_SB(sb)->s_journal;
 	if (journal != NULL)
-		return jbd2_journal_try_to_free_buffers(journal, page, wait);
+		return jbd2_journal_try_to_free_metadata_buffers(journal, page, wait);
 	else
 		return try_to_free_buffers(page);
 }
--
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