From 02ee654d3a04563c67bfe658a05384548b9bb105 Mon Sep 17 00:00:00 2001 From: Anand Jain Date: Thu, 17 May 2018 15:16:51 +0800 Subject: btrfs: fix crash when trying to resume balance without the resume flag We set the BTRFS_BALANCE_RESUME flag in the btrfs_recover_balance() only, which isn't called during the remount. So when resuming from the paused balance we hit the bug: kernel: kernel BUG at fs/btrfs/volumes.c:3890! :: kernel: balance_kthread+0x51/0x60 [btrfs] kernel: kthread+0x111/0x130 :: kernel: RIP: btrfs_balance+0x12e1/0x1570 [btrfs] RSP: ffffba7d0090bde8 Reproducer: On a mounted filesystem: btrfs balance start --full-balance /btrfs btrfs balance pause /btrfs mount -o remount,ro /dev/sdb /btrfs mount -o remount,rw /dev/sdb /btrfs To fix this set the BTRFS_BALANCE_RESUME flag in btrfs_resume_balance_async(). CC: stable@vger.kernel.org # 4.4+ Signed-off-by: Anand Jain Reviewed-by: David Sterba Signed-off-by: David Sterba --- fs/btrfs/volumes.c | 9 +++++++++ 1 file changed, 9 insertions(+) (limited to 'fs') diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c index 292266f6ab9c..be3fc701f389 100644 --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -4052,6 +4052,15 @@ int btrfs_resume_balance_async(struct btrfs_fs_info *fs_info) return 0; } + /* + * A ro->rw remount sequence should continue with the paused balance + * regardless of who pauses it, system or the user as of now, so set + * the resume flag. + */ + spin_lock(&fs_info->balance_lock); + fs_info->balance_ctl->flags |= BTRFS_BALANCE_RESUME; + spin_unlock(&fs_info->balance_lock); + tsk = kthread_run(balance_kthread, fs_info, "btrfs-balance"); return PTR_ERR_OR_ZERO(tsk); } -- cgit v1.2.3-59-g8ed1b