Btrfs: fix scheduler warning when syncing log
We try to lock a mutex while the current task state is not TASK_RUNNING,
which results in the following warning when CONFIG_DEBUG_LOCK_ALLOC=y:
[30736.772501] ------------[ cut here ]------------
[30736.774545] WARNING: CPU: 9 PID: 19972 at kernel/sched/core.c:7300 __might_sleep+0x8b/0xa8()
[30736.783453] do not call blocking ops when !TASK_RUNNING; state=2 set at [<ffffffff8107499b>] prepare_to_wait+0x43/0x89
[30736.786261] Modules linked in: dm_flakey dm_mod crc32c_generic btrfs xor raid6_pq nfsd auth_rpcgss oid_registry nfs_acl nfs lockd grace fscache sunrpc loop parport_pc psmouse parport pcspkr microcode serio_raw evdev processor thermal_sys i2c_piix4 i2c_core button ext4 crc16 jbd2 mbcache sg sr_mod cdrom sd_mod ata_generic virtio_scsi floppy ata_piix libata virtio_pci virtio_ring e1000 virtio scsi_mod
[30736.794323] CPU: 9 PID: 19972 Comm: fsstress Not tainted 3.19.0-rc7-btrfs-next-5+ #1
[30736.795821] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.7.5-0-ge51488c-20140602_164612-nilsson.home.kraxel.org 04/01/2014
[30736.798788] 0000000000000009 ffff88042743fbd8 ffffffff814248ed ffff88043d32f2d8
[30736.800504] ffff88042743fc28 ffff88042743fc18 ffffffff81045338 0000000000000001
[30736.802131] ffffffff81064514 ffffffff817c52d1 000000000000026d 0000000000000000
[30736.803676] Call Trace:
[30736.804256] [<ffffffff814248ed>] dump_stack+0x4c/0x65
[30736.805245] [<ffffffff81045338>] warn_slowpath_common+0xa1/0xbb
[30736.806360] [<ffffffff81064514>] ? __might_sleep+0x8b/0xa8
[30736.807391] [<ffffffff81045398>] warn_slowpath_fmt+0x46/0x48
[30736.808511] [<ffffffff8107499b>] ? prepare_to_wait+0x43/0x89
[30736.809620] [<ffffffff8107499b>] ? prepare_to_wait+0x43/0x89
[30736.810691] [<ffffffff81064514>] __might_sleep+0x8b/0xa8
[30736.811703] [<ffffffff81426eaf>] mutex_lock_nested+0x2f/0x3a0
[30736.812889] [<ffffffff8107bfa1>] ? trace_hardirqs_on_caller+0x18f/0x1ab
[30736.814138] [<ffffffff8107bfca>] ? trace_hardirqs_on+0xd/0xf
[30736.819878] [<ffffffffa038cfff>] wait_for_writer.isra.12+0x91/0xaa [btrfs]
[30736.821260] [<ffffffff810748bd>] ? signal_pending_state+0x31/0x31
[30736.822410] [<ffffffffa0391f0a>] btrfs_sync_log+0x160/0x947 [btrfs]
[30736.823574] [<ffffffff8107bfa1>] ? trace_hardirqs_on_caller+0x18f/0x1ab
[30736.824847] [<ffffffff8107bfca>] ? trace_hardirqs_on+0xd/0xf
[30736.825972] [<ffffffffa036e555>] btrfs_sync_file+0x2b0/0x319 [btrfs]
[30736.827684] [<ffffffff8117901a>] vfs_fsync_range+0x21/0x23
[30736.828932] [<ffffffff81179038>] vfs_fsync+0x1c/0x1e
[30736.829917] [<ffffffff8117928b>] do_fsync+0x34/0x4e
[30736.830862] [<ffffffff811794b3>] SyS_fsync+0x10/0x14
[30736.831819] [<ffffffff8142a512>] system_call_fastpath+0x12/0x17
[30736.832982] ---[ end trace c0b57df60d32ae5c ]---
Fix this my acquiring the mutex after calling finish_wait(), which sets the
task's state to TASK_RUNNING.
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: Liu Bo <bo.li.liu@oracle.com>
Signed-off-by: Chris Mason <clm@fb.com>
diff --git a/fs/btrfs/tree-log.c b/fs/btrfs/tree-log.c
index 79f05bc..7870bdb 100644
--- a/fs/btrfs/tree-log.c
+++ b/fs/btrfs/tree-log.c
@@ -2448,8 +2448,8 @@
mutex_unlock(&root->log_mutex);
if (atomic_read(&root->log_writers))
schedule();
- mutex_lock(&root->log_mutex);
finish_wait(&root->log_writer_wait, &wait);
+ mutex_lock(&root->log_mutex);
}
}