Btrfs

Hi Linus,

We have two more fixes in my for-linus branch:

git://git.kernel.org/pub/scm/linux/kernel/git/mason/linux-btrfs.git for-linus

I was hoping to also include a fix for a btrfs deadlock with compression enabled, but we're still nailing that one down.

Liu Bo (1) commits (+11/-0):
Btrfs: fix abnormal long waiting in fsync

Eric Sandeen (1) commits (+4/-4):
btrfs: test for valid bdev before kobj removal in btrfs_rm_device

Total: (2) commits (+15/-4)

 fs/btrfs/ordered-data.c | 11 +++++++++++
 fs/btrfs/volumes.c      |  8 ++++----
 2 files changed, 15 insertions(+), 4 deletions(-)

Chris Mason posted on Sun, 20 Jul 2014 10:33:24 -0400 as excerpted:

FWIW, I might be (rarely but twice, now) hitting that one myself, compress=lzo, but /not/ with the rsync that has been your current primary trigger.

The last time I hit it, it was trying to start firefox shortly after a fresh boot. Firefox didn't come up, and when I tried starting it again, I got the dialog saying it was already running, quit the running instance and try again, or reboot.

But the running firefox instance was stuck unkillable in D state, with a zombie child. Three of my six cores were stuck in 100% IO-wait.

I finished what I was doing and shut down X, but of course the D-state and zombie firefox reparented to systemd. The time before when that happened with firefox, I ended up losing several of the firefox state files and it forgot my extensions, which I had to restore from backup. So this time I mounted a reiserfs I use for other things and did a backup of the entire ~/.mozilla/ subdir before finishing the shutdown and reboot. That backup went fine (surprised me, I thought it might hang too), and I umounted the reiserfs. But when I went to finish the shutdown of course the affected btrfs wouldn't umount due to the stuck firefox. So I did the magic-SRQ REISUB thing, and saw the emergency sync and the remount-read-only complete.

After that I force-rebooted. Luckily, this time I didn't need that backup of the ~/.mozilla subfolder I had made -- firefox came up fine after the reboot. But I did lose the read state on a few messages in my feed (rss/atom) and news (nntp) readers, so I think btrfs did lose the log from after the last root-tree commit point.

Duncan - List replies preferred.   No HTML msgs.
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