From 2562c322404d81ee5fa82f3cf601a2e27393ab57 Mon Sep 17 00:00:00 2001 From: Dave Chinner Date: Tue, 10 Aug 2021 18:00:41 -0700 Subject: [PATCH] xfs: log head and tail aren't reliable during shutdown I'm seeing assert failures from xlog_space_left() after a shutdown has begun that look like: XFS (dm-0): log I/O error -5 XFS (dm-0): xfs_do_force_shutdown(0x2) called from line 1338 of file fs/xfs/xfs_log.c. Return address = xlog_ioend_work+0x64/0xc0 XFS (dm-0): Log I/O Error Detected. XFS (dm-0): Shutting down filesystem. Please unmount the filesystem and rectify the problem(s) XFS (dm-0): xlog_space_left: head behind tail XFS (dm-0): tail_cycle = 6, tail_bytes = 2706944 XFS (dm-0): GH cycle = 6, GH bytes = 1633867 XFS: Assertion failed: 0, file: fs/xfs/xfs_log.c, line: 1310 ------------[ cut here ]------------ Call Trace: xlog_space_left+0xc3/0x110 xlog_grant_push_threshold+0x3f/0xf0 xlog_grant_push_ail+0x12/0x40 xfs_log_reserve+0xd2/0x270 ? __might_sleep+0x4b/0x80 xfs_trans_reserve+0x18b/0x260 ..... There are two things here. Firstly, after a shutdown, the log head and tail can be out of whack as things abort and release (or don't release) resources, so checking them for sanity doesn't make much sense. Secondly, xfs_log_reserve() can race with shutdown and so it can still fail like this even though it has already checked for a log shutdown before calling xlog_grant_push_ail(). So, before ASSERT failing in xlog_space_left(), make sure we haven't already shut down.... Signed-off-by: Dave Chinner Reviewed-by: Christoph Hellwig Reviewed-by: Darrick J. Wong Signed-off-by: Darrick J. Wong --- fs/xfs/xfs_log.c | 51 +++++++++++++++++++++++++----------------------- 1 file changed, 27 insertions(+), 24 deletions(-) diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c index a4ec23b5c459..a26c7909cbe7 100644 --- a/fs/xfs/xfs_log.c +++ b/fs/xfs/xfs_log.c @@ -1307,16 +1307,18 @@ xlog_assign_tail_lsn( * wrap the tail, we should blow up. Rather than catch this case here, * we depend on other ASSERTions in other parts of the code. XXXmiken * - * This code also handles the case where the reservation head is behind - * the tail. The details of this case are described below, but the end - * result is that we return the size of the log as the amount of space left. + * If reservation head is behind the tail, we have a problem. Warn about it, + * but then treat it as if the log is empty. + * + * If the log is shut down, the head and tail may be invalid or out of whack, so + * shortcut invalidity asserts in this case so that we don't trigger them + * falsely. */ STATIC int xlog_space_left( struct xlog *log, atomic64_t *head) { - int free_bytes; int tail_bytes; int tail_cycle; int head_cycle; @@ -1326,29 +1328,30 @@ xlog_space_left( xlog_crack_atomic_lsn(&log->l_tail_lsn, &tail_cycle, &tail_bytes); tail_bytes = BBTOB(tail_bytes); if (tail_cycle == head_cycle && head_bytes >= tail_bytes) - free_bytes = log->l_logsize - (head_bytes - tail_bytes); - else if (tail_cycle + 1 < head_cycle) + return log->l_logsize - (head_bytes - tail_bytes); + if (tail_cycle + 1 < head_cycle) return 0; - else if (tail_cycle < head_cycle) { + + /* Ignore potential inconsistency when shutdown. */ + if (xlog_is_shutdown(log)) + return log->l_logsize; + + if (tail_cycle < head_cycle) { ASSERT(tail_cycle == (head_cycle - 1)); - free_bytes = tail_bytes - head_bytes; - } else { - /* - * The reservation head is behind the tail. - * In this case we just want to return the size of the - * log as the amount of space left. - */ - xfs_alert(log->l_mp, "xlog_space_left: head behind tail"); - xfs_alert(log->l_mp, - " tail_cycle = %d, tail_bytes = %d", - tail_cycle, tail_bytes); - xfs_alert(log->l_mp, - " GH cycle = %d, GH bytes = %d", - head_cycle, head_bytes); - ASSERT(0); - free_bytes = log->l_logsize; + return tail_bytes - head_bytes; } - return free_bytes; + + /* + * The reservation head is behind the tail. In this case we just want to + * return the size of the log as the amount of space left. + */ + xfs_alert(log->l_mp, "xlog_space_left: head behind tail"); + xfs_alert(log->l_mp, " tail_cycle = %d, tail_bytes = %d", + tail_cycle, tail_bytes); + xfs_alert(log->l_mp, " GH cycle = %d, GH bytes = %d", + head_cycle, head_bytes); + ASSERT(0); + return log->l_logsize; }