[4.5-rc2] Revert "btrfs: clear PF_NOFREEZE in cleaner_kthread()"
diff mbox

Message ID 1453716126-7282-1-git-send-email-dsterba@suse.com
State New
Headers show

Commit Message

David Sterba Jan. 25, 2016, 10:02 a.m. UTC
This reverts commit 696249132158014d594896df3a81390616069c5c. The
cleaner thread can block freezing when there's a snapshot cleaning in
progress and the other threads get suspended first. From the logs
provided by Martin we're waiting for reading extent pages:

kernel: PM: Syncing filesystems ... done.
kernel: Freezing user space processes ... (elapsed 0.015 seconds) done.
kernel: Freezing remaining freezable tasks ...
kernel: Freezing of tasks failed after 20.003 seconds (1 tasks refusing to freeze, wq_busy=0):
kernel: btrfs-cleaner   D ffff88033dd13bc0     0   152      2 0x00000000
kernel: ffff88032ebc2e00 ffff88032e750000 ffff88032e74fa50 7fffffffffffffff
kernel: ffffffff814a58df 0000000000000002 ffffea000934d580 ffffffff814a5451
kernel: 7fffffffffffffff ffffffff814a6e8f 0000000000000000 0000000000000020
kernel: Call Trace:
kernel: [<ffffffff814a58df>] ? bit_wait+0x2c/0x2c
kernel: [<ffffffff814a5451>] ? schedule+0x6f/0x7c
kernel: [<ffffffff814a6e8f>] ? schedule_timeout+0x2f/0xd8
kernel: [<ffffffff81076f94>] ? timekeeping_get_ns+0xa/0x2e
kernel: [<ffffffff81077603>] ? ktime_get+0x36/0x44
kernel: [<ffffffff814a4f6c>] ? io_schedule_timeout+0x94/0xf2
kernel: [<ffffffff814a4f6c>] ? io_schedule_timeout+0x94/0xf2
kernel: [<ffffffff814a590b>] ? bit_wait_io+0x2c/0x30
kernel: [<ffffffff814a5694>] ? __wait_on_bit+0x41/0x73
kernel: [<ffffffff8109eba8>] ? wait_on_page_bit+0x6d/0x72
kernel: [<ffffffff8105d718>] ? autoremove_wake_function+0x2a/0x2a
kernel: [<ffffffff811a02d7>] ? read_extent_buffer_pages+0x1bd/0x203
kernel: [<ffffffff8117d9e9>] ? free_root_pointers+0x4c/0x4c
kernel: [<ffffffff8117e831>] ? btree_read_extent_buffer_pages.constprop.57+0x5a/0xe9
kernel: [<ffffffff8117f4f3>] ? read_tree_block+0x2d/0x45
kernel: [<ffffffff8116782a>] ? read_block_for_search.isra.34+0x22a/0x26b
kernel: [<ffffffff811656c3>] ? btrfs_set_path_blocking+0x1e/0x4a
kernel: [<ffffffff8116919b>] ? btrfs_search_slot+0x648/0x736
kernel: [<ffffffff81170559>] ? btrfs_lookup_extent_info+0xb7/0x2c7
kernel: [<ffffffff81170ee5>] ? walk_down_proc+0x9c/0x1ae
kernel: [<ffffffff81171c9d>] ? walk_down_tree+0x40/0xa4
kernel: [<ffffffff8117375f>] ? btrfs_drop_snapshot+0x2da/0x664
kernel: [<ffffffff8104ff21>] ? finish_task_switch+0x126/0x167
kernel: [<ffffffff811850f8>] ? btrfs_clean_one_deleted_snapshot+0xa6/0xb0
kernel: [<ffffffff8117eaba>] ? cleaner_kthread+0x13e/0x17b
kernel: [<ffffffff8117e97c>] ? btrfs_item_end+0x33/0x33
kernel: [<ffffffff8104d256>] ? kthread+0x95/0x9d
kernel: [<ffffffff8104d1c1>] ? kthread_parkme+0x16/0x16
kernel: [<ffffffff814a7b5f>] ? ret_from_fork+0x3f/0x70
kernel: [<ffffffff8104d1c1>] ? kthread_parkme+0x16/0x16

As this affects a released kernel (4.4) we need a minimal fix for
stable kernels.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=108361
Reported-by: Martin Ziegler <ziegler@uni-freiburg.de>
CC: stable@vger.kernel.org # 4.4
CC: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: David Sterba <dsterba@suse.com>
---
 fs/btrfs/disk-io.c | 1 -
 1 file changed, 1 deletion(-)

Comments

Jiri Kosina Jan. 25, 2016, 12:28 p.m. UTC | #1
On Mon, 25 Jan 2016, David Sterba wrote:

> This reverts commit 696249132158014d594896df3a81390616069c5c. The
> cleaner thread can block freezing when there's a snapshot cleaning in
> progress and the other threads get suspended first. From the logs
> provided by Martin we're waiting for reading extent pages:
> 
> kernel: PM: Syncing filesystems ... done.
> kernel: Freezing user space processes ... (elapsed 0.015 seconds) done.
> kernel: Freezing remaining freezable tasks ...
> kernel: Freezing of tasks failed after 20.003 seconds (1 tasks refusing to freeze, wq_busy=0):
> kernel: btrfs-cleaner   D ffff88033dd13bc0     0   152      2 0x00000000
> kernel: ffff88032ebc2e00 ffff88032e750000 ffff88032e74fa50 7fffffffffffffff
> kernel: ffffffff814a58df 0000000000000002 ffffea000934d580 ffffffff814a5451
> kernel: 7fffffffffffffff ffffffff814a6e8f 0000000000000000 0000000000000020
> kernel: Call Trace:
> kernel: [<ffffffff814a58df>] ? bit_wait+0x2c/0x2c
> kernel: [<ffffffff814a5451>] ? schedule+0x6f/0x7c
> kernel: [<ffffffff814a6e8f>] ? schedule_timeout+0x2f/0xd8
> kernel: [<ffffffff81076f94>] ? timekeeping_get_ns+0xa/0x2e
> kernel: [<ffffffff81077603>] ? ktime_get+0x36/0x44
> kernel: [<ffffffff814a4f6c>] ? io_schedule_timeout+0x94/0xf2
> kernel: [<ffffffff814a4f6c>] ? io_schedule_timeout+0x94/0xf2
> kernel: [<ffffffff814a590b>] ? bit_wait_io+0x2c/0x30
> kernel: [<ffffffff814a5694>] ? __wait_on_bit+0x41/0x73
> kernel: [<ffffffff8109eba8>] ? wait_on_page_bit+0x6d/0x72
> kernel: [<ffffffff8105d718>] ? autoremove_wake_function+0x2a/0x2a
> kernel: [<ffffffff811a02d7>] ? read_extent_buffer_pages+0x1bd/0x203
> kernel: [<ffffffff8117d9e9>] ? free_root_pointers+0x4c/0x4c
> kernel: [<ffffffff8117e831>] ? btree_read_extent_buffer_pages.constprop.57+0x5a/0xe9
> kernel: [<ffffffff8117f4f3>] ? read_tree_block+0x2d/0x45
> kernel: [<ffffffff8116782a>] ? read_block_for_search.isra.34+0x22a/0x26b
> kernel: [<ffffffff811656c3>] ? btrfs_set_path_blocking+0x1e/0x4a
> kernel: [<ffffffff8116919b>] ? btrfs_search_slot+0x648/0x736
> kernel: [<ffffffff81170559>] ? btrfs_lookup_extent_info+0xb7/0x2c7
> kernel: [<ffffffff81170ee5>] ? walk_down_proc+0x9c/0x1ae
> kernel: [<ffffffff81171c9d>] ? walk_down_tree+0x40/0xa4
> kernel: [<ffffffff8117375f>] ? btrfs_drop_snapshot+0x2da/0x664
> kernel: [<ffffffff8104ff21>] ? finish_task_switch+0x126/0x167
> kernel: [<ffffffff811850f8>] ? btrfs_clean_one_deleted_snapshot+0xa6/0xb0
> kernel: [<ffffffff8117eaba>] ? cleaner_kthread+0x13e/0x17b
> kernel: [<ffffffff8117e97c>] ? btrfs_item_end+0x33/0x33
> kernel: [<ffffffff8104d256>] ? kthread+0x95/0x9d
> kernel: [<ffffffff8104d1c1>] ? kthread_parkme+0x16/0x16
> kernel: [<ffffffff814a7b5f>] ? ret_from_fork+0x3f/0x70
> kernel: [<ffffffff8104d1c1>] ? kthread_parkme+0x16/0x16

Proper fix should be calling

	freezable_schedule()

instead of

	schedule()

at the end of the main kthread loop.

Calling try_to_freeze() on a non-freezable thread doesn't make any sense, 
so while I agree with the revert for -stable, I don't think the code 
should be kept as-is.
Chris Mason Jan. 26, 2016, 12:34 a.m. UTC | #2
On Mon, Jan 25, 2016 at 11:02:06AM +0100, David Sterba wrote:
> This reverts commit 696249132158014d594896df3a81390616069c5c. The
> cleaner thread can block freezing when there's a snapshot cleaning in
> progress and the other threads get suspended first. From the logs
> provided by Martin we're waiting for reading extent pages:

Sorry, I specifically looked for this kind of interaction when I took
the patch and missed it.

I'll revert for rc2.

-chris

> 
> kernel: PM: Syncing filesystems ... done.
> kernel: Freezing user space processes ... (elapsed 0.015 seconds) done.
> kernel: Freezing remaining freezable tasks ...
> kernel: Freezing of tasks failed after 20.003 seconds (1 tasks refusing to freeze, wq_busy=0):
> kernel: btrfs-cleaner   D ffff88033dd13bc0     0   152      2 0x00000000
> kernel: ffff88032ebc2e00 ffff88032e750000 ffff88032e74fa50 7fffffffffffffff
> kernel: ffffffff814a58df 0000000000000002 ffffea000934d580 ffffffff814a5451
> kernel: 7fffffffffffffff ffffffff814a6e8f 0000000000000000 0000000000000020
> kernel: Call Trace:
> kernel: [<ffffffff814a58df>] ? bit_wait+0x2c/0x2c
> kernel: [<ffffffff814a5451>] ? schedule+0x6f/0x7c
> kernel: [<ffffffff814a6e8f>] ? schedule_timeout+0x2f/0xd8
> kernel: [<ffffffff81076f94>] ? timekeeping_get_ns+0xa/0x2e
> kernel: [<ffffffff81077603>] ? ktime_get+0x36/0x44
> kernel: [<ffffffff814a4f6c>] ? io_schedule_timeout+0x94/0xf2
> kernel: [<ffffffff814a4f6c>] ? io_schedule_timeout+0x94/0xf2
> kernel: [<ffffffff814a590b>] ? bit_wait_io+0x2c/0x30
> kernel: [<ffffffff814a5694>] ? __wait_on_bit+0x41/0x73
> kernel: [<ffffffff8109eba8>] ? wait_on_page_bit+0x6d/0x72
> kernel: [<ffffffff8105d718>] ? autoremove_wake_function+0x2a/0x2a
> kernel: [<ffffffff811a02d7>] ? read_extent_buffer_pages+0x1bd/0x203
> kernel: [<ffffffff8117d9e9>] ? free_root_pointers+0x4c/0x4c
> kernel: [<ffffffff8117e831>] ? btree_read_extent_buffer_pages.constprop.57+0x5a/0xe9
> kernel: [<ffffffff8117f4f3>] ? read_tree_block+0x2d/0x45
> kernel: [<ffffffff8116782a>] ? read_block_for_search.isra.34+0x22a/0x26b
> kernel: [<ffffffff811656c3>] ? btrfs_set_path_blocking+0x1e/0x4a
> kernel: [<ffffffff8116919b>] ? btrfs_search_slot+0x648/0x736
> kernel: [<ffffffff81170559>] ? btrfs_lookup_extent_info+0xb7/0x2c7
> kernel: [<ffffffff81170ee5>] ? walk_down_proc+0x9c/0x1ae
> kernel: [<ffffffff81171c9d>] ? walk_down_tree+0x40/0xa4
> kernel: [<ffffffff8117375f>] ? btrfs_drop_snapshot+0x2da/0x664
> kernel: [<ffffffff8104ff21>] ? finish_task_switch+0x126/0x167
> kernel: [<ffffffff811850f8>] ? btrfs_clean_one_deleted_snapshot+0xa6/0xb0
> kernel: [<ffffffff8117eaba>] ? cleaner_kthread+0x13e/0x17b
> kernel: [<ffffffff8117e97c>] ? btrfs_item_end+0x33/0x33
> kernel: [<ffffffff8104d256>] ? kthread+0x95/0x9d
> kernel: [<ffffffff8104d1c1>] ? kthread_parkme+0x16/0x16
> kernel: [<ffffffff814a7b5f>] ? ret_from_fork+0x3f/0x70
> kernel: [<ffffffff8104d1c1>] ? kthread_parkme+0x16/0x16
> 
> As this affects a released kernel (4.4) we need a minimal fix for
> stable kernels.
> 
> Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=108361
> Reported-by: Martin Ziegler <ziegler@uni-freiburg.de>
> CC: stable@vger.kernel.org # 4.4
> CC: Jiri Kosina <jkosina@suse.cz>
> Signed-off-by: David Sterba <dsterba@suse.com>
> ---
>  fs/btrfs/disk-io.c | 1 -
>  1 file changed, 1 deletion(-)
> 
> diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
> index 26ef14152093..404e894c33d9 100644
> --- a/fs/btrfs/disk-io.c
> +++ b/fs/btrfs/disk-io.c
> @@ -1787,7 +1787,6 @@ static int cleaner_kthread(void *arg)
>  	int again;
>  	struct btrfs_trans_handle *trans;
>  
> -	set_freezable();
>  	do {
>  		again = 0;
>  
> -- 
> 2.6.3
> 
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Patch
diff mbox

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 26ef14152093..404e894c33d9 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -1787,7 +1787,6 @@  static int cleaner_kthread(void *arg)
 	int again;
 	struct btrfs_trans_handle *trans;
 
-	set_freezable();
 	do {
 		again = 0;