From 1307bbd2af67283131728637e9489002adb26f10 Mon Sep 17 00:00:00 2001 From: Ben Myers Date: Tue, 15 May 2012 14:26:55 -0500 Subject: [PATCH] xfs: protect xfs_sync_worker with s_umount semaphore xfs_sync_worker checks the MS_ACTIVE flag in s_flags to avoid doing work during mount and unmount. This flag can be cleared by unmount after the xfs_sync_worker checks it but before the work is completed. The has caused crashes in the completion handler for the dummy transaction commited by xfs_sync_worker: PID: 27544 TASK: ffff88013544e040 CPU: 3 COMMAND: "kworker/3:0" #0 [ffff88016fdff930] machine_kexec at ffffffff810244e9 #1 [ffff88016fdff9a0] crash_kexec at ffffffff8108d053 #2 [ffff88016fdffa70] oops_end at ffffffff813ad1b8 #3 [ffff88016fdffaa0] no_context at ffffffff8102bd48 #4 [ffff88016fdffaf0] __bad_area_nosemaphore at ffffffff8102c04d #5 [ffff88016fdffb40] bad_area_nosemaphore at ffffffff8102c12e #6 [ffff88016fdffb50] do_page_fault at ffffffff813afaee #7 [ffff88016fdffc60] page_fault at ffffffff813ac635 [exception RIP: xlog_get_lowest_lsn+0x30] RIP: ffffffffa04a9910 RSP: ffff88016fdffd10 RFLAGS: 00010246 RAX: ffffc90014e48000 RBX: ffff88014d879980 RCX: ffff88014d879980 RDX: ffff8802214ee4c0 RSI: 0000000000000000 RDI: 0000000000000000 RBP: ffff88016fdffd10 R8: ffff88014d879a80 R9: 0000000000000000 R10: 0000000000000001 R11: 0000000000000000 R12: ffff8802214ee400 R13: ffff88014d879980 R14: 0000000000000000 R15: ffff88022fd96605 ORIG_RAX: ffffffffffffffff CS: 0010 SS: 0018 #8 [ffff88016fdffd18] xlog_state_do_callback at ffffffffa04aa186 [xfs] #9 [ffff88016fdffd98] xlog_state_done_syncing at ffffffffa04aa568 [xfs] Protect xfs_sync_worker by using the s_umount semaphore at the read level to provide exclusion with unmount while work is progressing. Reviewed-by: Mark Tinguely Signed-off-by: Ben Myers --- fs/xfs/xfs_sync.c | 29 ++++++++++++++++------------- 1 file changed, 16 insertions(+), 13 deletions(-) diff --git a/fs/xfs/xfs_sync.c b/fs/xfs/xfs_sync.c index d2422683ed76..c9d3409c5ca3 100644 --- a/fs/xfs/xfs_sync.c +++ b/fs/xfs/xfs_sync.c @@ -386,20 +386,23 @@ xfs_sync_worker( * We shouldn't write/force the log if we are in the mount/unmount * process or on a read only filesystem. The workqueue still needs to be * active in both cases, however, because it is used for inode reclaim - * during these times. hence use the MS_ACTIVE flag to avoid doing - * anything in these periods. + * during these times. Use the s_umount semaphore to provide exclusion + * with unmount. */ - if (!(mp->m_super->s_flags & MS_ACTIVE) && - !(mp->m_flags & XFS_MOUNT_RDONLY)) { - /* dgc: errors ignored here */ - if (mp->m_super->s_frozen == SB_UNFROZEN && - xfs_log_need_covered(mp)) - error = xfs_fs_log_dummy(mp); - else - xfs_log_force(mp, 0); - - /* start pushing all the metadata that is currently dirty */ - xfs_ail_push_all(mp->m_ail); + if (down_read_trylock(&mp->m_super->s_umount)) { + if (!(mp->m_flags & XFS_MOUNT_RDONLY)) { + /* dgc: errors ignored here */ + if (mp->m_super->s_frozen == SB_UNFROZEN && + xfs_log_need_covered(mp)) + error = xfs_fs_log_dummy(mp); + else + xfs_log_force(mp, 0); + + /* start pushing all the metadata that is currently + * dirty */ + xfs_ail_push_all(mp->m_ail); + } + up_read(&mp->m_super->s_umount); } /* queue us up again */