Commits
Ben Myers committed 1307bbd2af6
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 <tinguely@sgi.com>
Signed-off-by: Ben Myers <bpm@sgi.com>