This is a note to let you know that I've just added the patch titled
nilfs2: fix deadlock of segment constructor during recovery
to the 3.19-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
nilfs2-fix-deadlock-of-segment-constructor-during-recovery.patch
and it can be found in the queue-3.19 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 283ee1482f349d6c0c09dfb725db5880afc56813 Mon Sep 17 00:00:00 2001
From: Ryusuke Konishi <konishi.ryusuke@xxxxxxxxxxxxx>
Date: Thu, 12 Mar 2015 16:26:00 -0700
Subject: nilfs2: fix deadlock of segment constructor during recovery
From: Ryusuke Konishi <konishi.ryusuke@xxxxxxxxxxxxx>
commit 283ee1482f349d6c0c09dfb725db5880afc56813 upstream.
According to a report from Yuxuan Shui, nilfs2 in kernel 3.19 got stuck
during recovery at mount time. The code path that caused the deadlock was
as follows:
nilfs_fill_super()
load_nilfs()
nilfs_salvage_orphan_logs()
* Do roll-forwarding, attach segment constructor for recovery,
and kick it.
nilfs_segctor_thread()
nilfs_segctor_thread_construct()
* A lock is held with nilfs_transaction_lock()
nilfs_segctor_do_construct()
nilfs_segctor_drop_written_files()
iput()
iput_final()
write_inode_now()
writeback_single_inode()
__writeback_single_inode()
do_writepages()
nilfs_writepage()
nilfs_construct_dsync_segment()
nilfs_transaction_lock() --> deadlock
This can happen if commit 7ef3ff2fea8b ("nilfs2: fix deadlock of segment
constructor over I_SYNC flag") is applied and roll-forward recovery was
performed at mount time. The roll-forward recovery can happen if datasync
write is done and the file system crashes immediately after that. For
instance, we can reproduce the issue with the following steps:
< nilfs2 is mounted on /nilfs (device: /dev/sdb1) >
# dd if=/dev/zero of=/nilfs/test bs=4k count=1 && sync
# dd if=/dev/zero of=/nilfs/test conv=notrunc oflag=dsync bs=4k
count=1 && reboot -nfh
< the system will immediately reboot >
# mount -t nilfs2 /dev/sdb1 /nilfs
The deadlock occurs because iput() can run segment constructor through
writeback_single_inode() if MS_ACTIVE flag is not set on sb->s_flags. The
above commit changed segment constructor so that it calls iput()
asynchronously for inodes with i_nlink == 0, but that change was
imperfect.
This fixes the another deadlock by deferring iput() in segment constructor
even for the case that mount is not finished, that is, for the case that
MS_ACTIVE flag is not set.
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@xxxxxxxxxxxxx>
Reported-by: Yuxuan Shui <yshuiv7@xxxxxxxxx>
Tested-by: Ryusuke Konishi <konishi.ryusuke@xxxxxxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/nilfs2/segment.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
--- a/fs/nilfs2/segment.c
+++ b/fs/nilfs2/segment.c
@@ -1907,6 +1907,7 @@ static void nilfs_segctor_drop_written_f
struct the_nilfs *nilfs)
{
struct nilfs_inode_info *ii, *n;
+ int during_mount = !(sci->sc_super->s_flags & MS_ACTIVE);
int defer_iput = false;
spin_lock(&nilfs->ns_inode_lock);
@@ -1919,10 +1920,10 @@ static void nilfs_segctor_drop_written_f
brelse(ii->i_bh);
ii->i_bh = NULL;
list_del_init(&ii->i_dirty);
- if (!ii->vfs_inode.i_nlink) {
+ if (!ii->vfs_inode.i_nlink || during_mount) {
/*
- * Defer calling iput() to avoid a deadlock
- * over I_SYNC flag for inodes with i_nlink == 0
+ * Defer calling iput() to avoid deadlocks if
+ * i_nlink == 0 or mount is not yet finished.
*/
list_add_tail(&ii->i_dirty, &sci->sc_iput_queue);
defer_iput = true;
Patches currently in stable-queue which might be from konishi.ryusuke@xxxxxxxxxxxxx are
queue-3.19/nilfs2-fix-deadlock-of-segment-constructor-during-recovery.patch
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