linux-ext4 - [PATCH] Attempt to sync the fsstress writes to a frozen F.S

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Wed, 11 May 2011 10:10:41 +0300
From:	Surbhi Palande <surbhi.palande@...onical.com>
To:	sandeen@...hat.com
Cc:	jack@...e.cz, marco.stornelli@...il.com, adilger.kernel@...ger.ca,
	toshi.okajima@...fujitsu.com, tytso@....edu,
	m.mizuma@...fujitsu.com, linux-ext4@...r.kernel.org,
	linux-fsdevel@...r.kernel.org
Subject: [PATCH] Attempt to sync the fsstress writes to a frozen F.S

While the fsstress background writes are busy dirtying the page cache, if a
fsfreeze happens then the background writes should stall. A sync should then
not have any data to sync to the FS. If it does have any data to sync then
sync will cause a deadlock by holding the s_umount write semaphore and waiting
in the wait queue for the FS to thaw, whereas the F.S can never thaw without
getting the s_umount write semaphore.

Signed-off-by: Surbhi Palande <surbhi.palande@...onical.com>
---
 068 |    5 +++++
 1 files changed, 5 insertions(+), 0 deletions(-)

diff --git a/068 b/068
index 82c1a4e..b9ac58d 100755
--- a/068
+++ b/068
@@ -101,6 +101,11 @@ do
 	    tee -a $seq.full
 	sleep 2
 
+	# there should be nothing to sync at this point. This may hang in case
+	# of fsstress background writes dirtying the page cache while the F.S is frozen
+	sync &
+	sleep 2
+
 	echo "*** thawing  \$SCRATCH_MNT" | tee -a $seq.full
 	xfs_freeze -u "$SCRATCH_MNT" | tee -a $seq.full
 	[ $? != 0 ] && echo xfs_freeze -u "$SCRATCH_MNT" failed | \
-- 
1.7.1

--
To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html