From: Dave Chinner <dchinner@xxxxxxxxxx> Upstream commit: 3948659e30808fbaa7673bbe89de2ae9769e20a7 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: Dave Chinner <dchinner@xxxxxxxxxx> Reviewed-by: Christoph Hellwig <hch@xxxxxx> Signed-off-by: Ben Myers <bpm@xxxxxxx> --- fs/xfs/xfs_log.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c index d92b442..653cba8 100644 --- a/fs/xfs/xfs_log.c +++ b/fs/xfs/xfs_log.c @@ -726,8 +726,9 @@ xfs_log_unmount_write(xfs_mount_t *mp) .lv_iovecp = ®, }; - /* 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); /* -- 1.7.10 _______________________________________________ xfs mailing list xfs@xxxxxxxxxxx http://oss.sgi.com/mailman/listinfo/xfs
