Re: Re: [PATCH] [PATCH] Stop periodic syncing if filesystem is already shutdown.

Raghavendra D Prabhu
2012-05-09T20:07:56Z

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Hi,

* On Tue, May 08, 2012 at 09:53:21AM +1000, Dave Chinner <david@fromorbit.com> wrote:
>On Mon, May 07, 2012 at 02:44:07PM +0530, raghu.prabhu13@gmail.com wrote:
>> From: Raghavendra D Prabhu <rprabhu@wnohang.net>
>>
>> This is to prevent syncing from running ad-infinitum till umount if the disk has been forcefully unplugged.
>>
>> This is to prevent messages like these from being displayed.
>.....
>> ---
>> fs/xfs/xfs_sync.c | 12 ++++++++++++
>> 1 file changed, 12 insertions(+)
>>
>> diff --git a/fs/xfs/xfs_sync.c b/fs/xfs/xfs_sync.c
>> index 205ebcb..7ec412c 100644
>> --- a/fs/xfs/xfs_sync.c
>> +++ b/fs/xfs/xfs_sync.c
>> @@ -460,6 +460,12 @@ xfs_sync_worker(
>> struct xfs_mount, m_sync_work);
>> int error;
>>
>> + if (!xfs_fs_writable(mp)) {
>> + xfs_err(mp, "Filesystem not writable / already shutdown.");
>> + xfs_syncd_stop(mp);
>> + return;
>> + }
>> +
>
>That is going to kill the xfssyncd on read only and frozen
>filesystems as well as shutdowns, so this is certainly not correct.
>The xfs_sync_worker should continue to run until the filesystem is
>unmounted, even if it does nothing when it runs.

Yes, in the next patch I had sent --
http://article.gmane.org/gmane.comp.file-systems.xfs.general/45568
-- I removed xfs_syncd_stop from there and added it under
xfs_bwrite.

(PS: Adding xfs_syncd_stop in xfs_sync_worker was a very
bad decision - it sent few of my kworkers to 'D' state and nearly
corrupted that fs)

>
>Indeed, all that is needed in xfs_sync_worker() is this:
>
>- if (!(mp->m_flags & XFS_MOUNT_RDONLY)) {
>+ if (!xfs_fs_writable(mp)) {
>
>and the error message won't appear. It fixes the problem for the
>shutdown case, as well as handles frozen and read-only filesystems
>correctly.

I realized from your earlier comment that, calling
xfs_syncd_stop under xfs_bwrite won't be good either;
so I was thinking of just checking for

XFS_FORCED_SHUTDOWN(mp) in xfs_log_force and bailing out
if already shutdown.

which should take care of xfs_sync_worker,
xfs_flush_worker, xfs_iflush and xfs_unmountfs

Does this sound good?

>
>> /* dgc: errors ignored here */
>> if (mp->m_super->s_frozen == SB_UNFROZEN &&
>> @@ -551,6 +557,12 @@ xfs_flush_worker(
>> struct xfs_mount *mp = container_of(work,
>> struct xfs_mount, m_flush_work);
>>
>> + if (!xfs_fs_writable(mp)) {
>> + xfs_err(mp, "Filesystem not writable / already shutdown.");
>> + xfs_syncd_stop(mp);
>> + return;
>> + }
>> +
>> xfs_sync_data(mp, SYNC_TRYLOCK);
>> xfs_sync_data(mp, SYNC_TRYLOCK | SYNC_WAIT);
>
>This is not necessary, either, because xfs_sync_data() has shutdown
>checks and xfs_flush_worker() should never be called on a shutdown
>filesystem....
Yeah, I realized that (sent a patch after this
http://article.gmane.org/gmane.comp.file-systems.xfs.general/45568).
>
>Cheers,
>
>Dave.
>--
>Dave Chinner
>david@fromorbit.com