This is a note to let you know that I've just added the patch titled
btrfs: fix lock dep warning move scratch super outside of chunk_mutex
to the 4.5-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:
btrfs-fix-lock-dep-warning-move-scratch-super-outside-of-chunk_mutex.patch
and it can be found in the queue-4.5 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 48b3b9d401ec86899a52003b37331190a35a81a6 Mon Sep 17 00:00:00 2001
From: Anand Jain <anand.jain@xxxxxxxxxx>
Date: Tue, 12 Apr 2016 21:36:16 +0800
Subject: btrfs: fix lock dep warning move scratch super outside of chunk_mutex
From: Anand Jain <anand.jain@xxxxxxxxxx>
commit 48b3b9d401ec86899a52003b37331190a35a81a6 upstream.
Move scratch super outside of the chunk lock to avoid below
lockdep warning. The better place to scratch super is in
the function btrfs_rm_dev_replace_free_srcdev() just before
free_device, which is outside of the chunk lock as well.
To reproduce:
(fresh boot)
mkfs.btrfs -f -draid5 -mraid5 /dev/sdc /dev/sdd /dev/sde
mount /dev/sdc /btrfs
dd if=/dev/zero of=/btrfs/tf1 bs=4096 count=100
(get devmgt from https://github.com/asj/devmgt.git)
devmgt detach /dev/sde
dd if=/dev/zero of=/btrfs/tf1 bs=4096 count=100
sync
btrfs replace start -Brf 3 /dev/sdf /btrfs <--
devmgt attach host7
======================================================
[ INFO: possible circular locking dependency detected ]
4.6.0-rc2asj+ #1 Not tainted
---------------------------------------------------
btrfs/2174 is trying to acquire lock:
(sb_writers){.+.+.+}, at:
[<ffffffff812449b4>] __sb_start_write+0xb4/0xf0
but task is already holding lock:
(&fs_info->chunk_mutex){+.+.+.}, at:
[<ffffffffa05c5f55>] btrfs_dev_replace_finishing+0x145/0x980 [btrfs]
which lock already depends on the new lock.
Chain exists of:
sb_writers --> &fs_devs->device_list_mutex --> &fs_info->chunk_mutex
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock(&fs_info->chunk_mutex);
lock(&fs_devs->device_list_mutex);
lock(&fs_info->chunk_mutex);
lock(sb_writers);
---
fs/btrfs/volumes.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -1971,11 +1971,8 @@ void btrfs_rm_dev_replace_remove_srcdev(
if (srcdev->missing)
fs_devices->missing_devices--;
- if (srcdev->writeable) {
+ if (srcdev->writeable)
fs_devices->rw_devices--;
- /* zero out the old super if it is writable */
- btrfs_scratch_superblocks(srcdev->bdev, srcdev->name->str);
- }
if (srcdev->bdev)
fs_devices->open_devices--;
@@ -1986,6 +1983,10 @@ void btrfs_rm_dev_replace_free_srcdev(st
{
struct btrfs_fs_devices *fs_devices = srcdev->fs_devices;
+ if (srcdev->writeable) {
+ /* zero out the old super if it is writable */
+ btrfs_scratch_superblocks(srcdev->bdev, srcdev->name->str);
+ }
call_rcu(&srcdev->rcu, free_device);
/*
Patches currently in stable-queue which might be from anand.jain@xxxxxxxxxx are
queue-4.5/btrfs-pass-the-right-error-code-to-the-btrfs_std_error.patch
queue-4.5/btrfs-fix-lock-dep-warning-move-scratch-super-outside-of-chunk_mutex.patch
queue-4.5/btrfs-fix-lock-dep-warning-move-scratch-dev-out-of-device_list_mutex-and-uuid_mutex.patch
--
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