On Mon, Jan 06, 2025 at 11:55:41AM -0800, Darrick J. Wong wrote:
> On Tue, Dec 31, 2024 at 10:34:23AM +0800, Long Li wrote:
> > 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(),
>
> What shuts it down? If xlog_recover_do_primary_sb_buffer trips over
> something like "mp->m_sb.sb_rgcount < orig_rgcount" then we haven't shut
> anything down yet. Am I missing something? <confused>
>
> --D
>
Hi Darrick,
Sorry for being unclear. I was referring to the shutdown in xlog_do_recovery_pass().
Here's the specific flow after the fix:
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 buffer_list
return error
...
if (!list_empty(&buffer_list))
if (error)
xlog_force_shutdown(log, SHUTDOWN_LOG_IO_ERROR); //log shutdown first
xfs_buf_delwri_submit(&buffer_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
It might be clearer to put this process into a commit message.
Thanks,
Long Li
