When mounting an image containing a log with sb modifications that require
log replay, the mount process hang all the time and stack as follows:
[root@localhost ~]# cat /proc/557/stack
[<0>] xfs_buftarg_wait+0x31/0x70
[<0>] xfs_buftarg_drain+0x54/0x350
[<0>] xfs_mountfs+0x66e/0xe80
[<0>] xfs_fs_fill_super+0x7f1/0xec0
[<0>] get_tree_bdev_flags+0x186/0x280
[<0>] get_tree_bdev+0x18/0x30
[<0>] xfs_fs_get_tree+0x1d/0x30
[<0>] vfs_get_tree+0x2d/0x110
[<0>] path_mount+0xb59/0xfc0
[<0>] do_mount+0x92/0xc0
[<0>] __x64_sys_mount+0xc2/0x160
[<0>] x64_sys_call+0x2de4/0x45c0
[<0>] do_syscall_64+0xa7/0x240
[<0>] entry_SYSCALL_64_after_hwframe+0x76/0x7e
During log recovery, while updating the in-memory superblock from the
primary SB buffer, if an error is encountered, such as superblock
corruption occurs or some other reasons, we will proceed to out_release
and release the xfs_buf. However, this is insufficient because the
xfs_buf's log item has already been initialized and the xfs_buf is held
by the buffer log item as follows, the xfs_buf will not be released,
causing the mount thread to hang.
xlog_recover_do_primary_sb_buffer
xlog_recover_do_reg_buffer
xlog_recover_validate_buf_type
xfs_buf_item_init(bp, mp)
The solution is straightforward, we simply need to allow it to be
handled by the normal buffer write process. The filesystem will be
shutdown before the submission of buffer_list in xlog_do_recovery_pass(),
ensuring the correct release of the xfs_buf as follows:
xlog_do_recovery_pass
error = xlog_recover_process
xlog_recover_process_data
xlog_recover_process_ophdr
xlog_recovery_process_trans
...
xlog_recover_buf_commit_pass2
error = xlog_recover_do_primary_sb_buffer
//Encounter error and return
if (error)
goto out_writebuf
...
out_writebuf:
xfs_buf_delwri_queue(bp, buffer_list) //add bp to list
return error
...
if (!list_empty(&buffer_list))
if (error)
xlog_force_shutdown(log, SHUTDOWN_LOG_IO_ERROR); //shutdown first
xfs_buf_delwri_submit(&buffer_list); //write buffer in list
__xfs_buf_submit
if (bp->b_mount->m_log && xlog_is_shutdown(bp->b_mount->m_log))
xfs_buf_ioend_fail(bp) //release bp correctly
Fixes: 6a18765b54e2 ("xfs: update the file system geometry after recoverying superblock buffers")
Signed-off-by: Long Li <leo.lilong@xxxxxxxxxx>
---
v1->v2: Add code comments and add the fixed stack description to the
commit message.
fs/xfs/xfs_buf_item_recover.c | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)
diff --git a/fs/xfs/xfs_buf_item_recover.c b/fs/xfs/xfs_buf_item_recover.c
index 3d0c6402cb36..04122bbdd5f3 100644
--- a/fs/xfs/xfs_buf_item_recover.c
+++ b/fs/xfs/xfs_buf_item_recover.c
@@ -1079,7 +1079,7 @@ xlog_recover_buf_commit_pass2(
error = xlog_recover_do_primary_sb_buffer(mp, item, bp, buf_f,
current_lsn);
if (error)
- goto out_release;
+ goto out_writebuf;
/* Update the rt superblock if we have one. */
if (xfs_has_rtsb(mp) && mp->m_rtsb_bp) {
@@ -1096,6 +1096,15 @@ xlog_recover_buf_commit_pass2(
xlog_recover_do_reg_buffer(mp, item, bp, buf_f, current_lsn);
}
+ /*
+ * Buffer held by buf log item during 'normal' buffer recovery must
+ * be committed through buffer I/O submission path to ensure proper
+ * release. When error occurs during do sb buffer recovery, log
+ * shutdown will be done before submitting buffer list so that buffers
+ * can be released correctly through ioend failure path.
+ */
+out_writebuf:
+
/*
* Perform delayed write on the buffer. Asynchronous writes will be
* slower when taking into account all the buffers to be flushed.
--
2.39.2
