xfs: make forced shutdown processing atomic

The running of a forced shutdown is a bit of a mess. It does racy
checks for XFS_MOUNT_SHUTDOWN in xfs_do_force_shutdown(), then
does more racy checks in xfs_log_force_unmount() before finally
setting XFS_MOUNT_SHUTDOWN and XLOG_IO_ERROR under the
log->icloglock.

Move the checking and setting of XFS_MOUNT_SHUTDOWN into
xfs_do_force_shutdown() so we only process a shutdown once and once
only. Serialise this with the mp->m_sb_lock spinlock so that the
state change is atomic and won't race. Move all the mount specific
shutdown state changes from xfs_log_force_unmount() to
xfs_do_force_shutdown() so they are done atomically with setting
XFS_MOUNT_SHUTDOWN.

Then get rid of the racy xlog_is_shutdown() check from
xlog_force_shutdown(), and gate the log shutdown on the
test_and_set_bit(XLOG_IO_ERROR) test under the icloglock. This
means that the log is shutdown once and once only, and code that
needs to prevent races with shutdown can do so by holding the
icloglock and checking the return value of xlog_is_shutdown().

This results in a predictable shutdown execution process - we set the
shutdown flags once and process the shutdown once rather than the
current "as many concurrent shutdowns as can race to the flag
setting" situation we have now.

Also, now that shutdown is atomic, alway emit a stack trace when the
error level for the filesystem is high enough. This means that we
always get a stack trace when trying to diagnose the cause of
shutdowns in the field, rather than just for SHUTDOWN_CORRUPT_INCORE
cases.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>

1 files changed, 1 insertions, 1 deletions

diff --git a/fs/xfs/xfs_log.h b/fs/xfs/xfs_log.h
index d1235f5073fe..8431a2f4bd13 100644
--- a/fs/xfs/xfs_log.h
+++ b/fs/xfs/xfs_log.h
@@ -125,7 +125,6 @@ int	  xfs_log_reserve(struct xfs_mount *mp,
 			  bool		   permanent);
 int	  xfs_log_regrant(struct xfs_mount *mp, struct xlog_ticket *tic);
 void      xfs_log_unmount(struct xfs_mount *mp);
-int	  xfs_log_force_umount(struct xfs_mount *mp, int logerror);
 bool	xfs_log_writable(struct xfs_mount *mp);
 
 struct xlog_ticket *xfs_log_ticket_get(struct xlog_ticket *ticket);
@@ -140,6 +139,7 @@ void	xfs_log_clean(struct xfs_mount *mp);
 bool	xfs_log_check_lsn(struct xfs_mount *, xfs_lsn_t);
 
 xfs_lsn_t xlog_grant_push_threshold(struct xlog *log, int need_bytes);
+bool	  xlog_force_shutdown(struct xlog *log, int shutdown_flags);
 
 void xlog_use_incompat_feat(struct xlog *log);
 void xlog_drop_incompat_feat(struct xlog *log);