linux-kernel - [PATCH 1/1] LogFS: Deadlock in logfs_get_wblocks, hold and wait on super->s_write

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Message-ID: <AANLkTi=BEkybzx4=cJoboXQbKsUb62Yrqz6RLoxd-Qyb@mail.gmail.com>
Date:	Tue, 16 Nov 2010 16:38:36 +0000
From:	Prasad Joshi <prasadjoshi124@...il.com>
To:	Linux Kernel <linux-kernel@...r.kernel.org>,
	linux-fsdevel@...nel.org, Joern <joern@...fs.org>,
	florian@...kler.org
Subject: [PATCH 1/1] LogFS: Deadlock in logfs_get_wblocks, hold and wait on super->s_write_mutex

do_logfs_journal_wl_pass() should use GFP_NOFS for memory allocation
GC code calls btree_insert32 with GFP_KERNEL while holding a mutex
super->s_write_mutex. The same mutex is used in
address_space_operations->writepage(). Call to writepage() could be triggered
as a result of memory allocation in btree_insert32, causing a deadlock.


Signed-off-by: Prasad Joshi <prasadjoshi124@...il.com>
---
diff --git a/fs/logfs/journal.c b/fs/logfs/journal.c
index f46ee8b..9da2970 100644
--- a/fs/logfs/journal.c
+++ b/fs/logfs/journal.c
@@ -828,7 +828,7 @@ void do_logfs_journal_wl_pass(struct super_block *sb)
         super->s_journal_seg[i] = segno;
         super->s_journal_ec[i] = ec;
         logfs_set_segment_reserved(sb, segno);
-        err = btree_insert32(head, segno, (void *)1, GFP_KERNEL);
+        err = btree_insert32(head, segno, (void *)1, GFP_NOFS);
         BUG_ON(err); /* mempool should prevent this */
         err = logfs_erase_segment(sb, segno, 1);
         BUG_ON(err); /* FIXME: remount-ro would be nicer */


---------- Forwarded message ----------
From: <bugzilla-daemon@...zilla.kernel.org>
Date: Tue, Nov 16, 2010 at 3:28 PM
Subject: [Bug 20342] [LogFS] [2.6.36-rc7] Deadlock in
logfs_get_wblocks, hold and wait on same lock super->s_write_mutex
To: prasadjoshi124@...il.com


https://bugzilla.kernel.org/show_bug.cgi?id=20342


Florian Mickler <florian@...kler.org> changed:

          What    |Removed                     |Added
----------------------------------------------------------------------------
                CC|                            |florian@...kler.org




--- Comment #2 from Florian Mickler <florian@...kler.org>  2010-11-16
15:27:59 ---
Please submit this patch on lkml and the logfs mailinglist for review. The
logfs maintainers seem to not be aware of the bugzilla.

( Documentation/SubmittingPatches )

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