Commit 3948659e authored by Dave Chinner's avatar Dave Chinner Committed by Ben Myers

xfs: Account log unmount transaction correctly

There have been a few reports of this warning appearing recently:

XFS (dm-4): xlog_space_left: head behind tail
 tail_cycle = 129, tail_bytes = 20163072
 GH   cycle = 129, GH   bytes = 20162880

The common cause appears to be lots of freeze and unfreeze cycles,
and the output from the warnings indicates that we are leaking
around 8 bytes of log space per freeze/unfreeze cycle.

When we freeze the filesystem, we write an unmount record and that
uses xlog_write directly - a special type of transaction,
effectively. What it doesn't do, however, is correctly account for
the log space it uses. The unmount record writes an 8 byte structure
with a special magic number into the log, and the space this
consumes is not accounted for in the log ticket tracking the
operation. Hence we leak 8 bytes every unmount record that is
written.
Signed-off-by: default avatarDave Chinner <dchinner@redhat.com>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarBen Myers <bpm@sgi.com>
parent 5132ba8f
......@@ -726,8 +726,9 @@ xfs_log_unmount_write(xfs_mount_t *mp)
.lv_iovecp = &reg,
};
/* remove inited flag */
/* remove inited flag, and account for space used */
tic->t_flags = 0;
tic->t_curr_res -= sizeof(magic);
error = xlog_write(log, &vec, tic, &lsn,
NULL, XLOG_UNMOUNT_TRANS);
/*
......
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