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Message-ID: <745754f6-0728-4682-95a0-39807675bb18@gmx.com>
Date: Mon, 2 Sep 2024 18:19:43 +0930
From: Qu Wenruo <quwenruo.btrfs@....com>
To: Luca Stefani <luca.stefani.ge1@...il.com>
Cc: Chris Mason <clm@...com>, Josef Bacik <josef@...icpanda.com>,
 David Sterba <dsterba@...e.com>, linux-btrfs@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH] btrfs: Don't block system suspend during fstrim



在 2024/9/2 18:02, Luca Stefani 写道:
> Any update on this? It's not critical but I'd like to know if it's in
> some part proper.
> Thanks, Luca.

Sorry I didn't see your patch in the list, thus sent a different fix for
it later:

https://lore.kernel.org/linux-btrfs/20240830185113.GW25962@twin.jikos.cz/T/#t

>> Sometimes the system isn't able to suspend because
>> the task responsible for trimming the device isn't
>> able to finish in time.
>>
>> Since discard isn't a critical call it can be interrupted
>> at any time, we can simply report the amount of discarded
>> bytes in such cases and stop the trim.
>>
>> Closes: https://bugzilla.kernel.org/show_bug.cgi?id=219180
>> Signed-off-by: Luca Stefani <luca.stefani.ge1@...il.com>
>> ---
>> I have no idea if that's correct, just something I implemented
>> looking at the same solution made in ext4 by 5229a658f645.
>>
>> The patch in itself seems to solve the issue.
>>
>> repro is as follows:
>> sudo /sbin/fstrim --listed-in /etc/fstab:/proc/self/mountinfo
>> --verbose --quiet-unsupported &
>> sudo ./sleepgraph.py -m mem -rtcwake 5
>>
>> [836563.289069] PM: suspend exit
>> [836563.909298] PM: suspend entry (s2idle)
>> [836563.935447] Filesystems sync: 0.026 seconds
>> [836563.951391] Freezing user space processes
>> [836583.958957] Freezing user space processes failed after 20.007
>> seconds (1 tasks refusing to freeze, wq_busy=0):
>> [836583.959582] task:fstrim          state:D stack:0     pid:241865
>> tgid:241865 ppid:241864 flags:0x00004006
>> [836583.959592] Call Trace:
>> [836583.959595]  <TASK>
>> [836583.959600]  __schedule+0x400/0x1720
>> [836583.959612]  ? mod_delayed_work_on+0xa4/0xb0
>> [836583.959622]  ? srso_alias_return_thunk+0x5/0xfbef5
>> [836583.959628]  ? srso_alias_return_thunk+0x5/0xfbef5
>> [836583.959631]  ? blk_mq_flush_plug_list.part.0+0x1e3/0x610
>> [836583.959640]  schedule+0x27/0xf0
>> [836583.959644]  schedule_timeout+0x12f/0x160
>> [836583.959652]  io_schedule_timeout+0x51/0x70
>> [836583.959657]  wait_for_completion_io+0x8a/0x160
>> [836583.959663]  submit_bio_wait+0x60/0x90
>> [836583.959671]  blkdev_issue_discard+0x91/0x100
>> [836583.959680]  btrfs_issue_discard+0xc4/0x140
>> [836583.959689]  btrfs_discard_extent+0x241/0x2a0
>> [836583.959695]  ? srso_alias_return_thunk+0x5/0xfbef5
>> [836583.959702]  do_trimming+0xd2/0x240
>> [836583.959712]  trim_bitmaps+0x350/0x4c0
>> [836583.959723]  btrfs_trim_block_group+0xb8/0x110
>> [836583.959729]  btrfs_trim_fs+0x118/0x440
>> [836583.959734]  ? srso_alias_return_thunk+0x5/0xfbef5
>> [836583.959738]  ? security_capable+0x41/0x70
>> [836583.959746]  btrfs_ioctl_fitrim+0x113/0x180
>> [836583.959752]  btrfs_ioctl+0xdaf/0x2670
>> [836583.959759]  ? srso_alias_return_thunk+0x5/0xfbef5
>> [836583.959763]  ? ioctl_has_perm.constprop.0.isra.0+0xd8/0x130
>> [836583.959774]  __x64_sys_ioctl+0x94/0xd0
>> [836583.959782]  do_syscall_64+0x82/0x160
>> [836583.959790]  ? srso_alias_return_thunk+0x5/0xfbef5
>> [836583.959793]  ? syscall_exit_to_user_mode+0x72/0x220
>> [836583.959799]  ? srso_alias_return_thunk+0x5/0xfbef5
>> [836583.959802]  ? do_syscall_64+0x8e/0x160
>> [836583.959807]  ? srso_alias_return_thunk+0x5/0xfbef5
>> [836583.959811]  ? do_sys_openat2+0x9c/0xe0
>> [836583.959821]  ? srso_alias_return_thunk+0x5/0xfbef5
>> [836583.959825]  ? syscall_exit_to_user_mode+0x72/0x220
>> [836583.959828]  ? srso_alias_return_thunk+0x5/0xfbef5
>> [836583.959832]  ? do_syscall_64+0x8e/0x160
>> [836583.959835]  ? syscall_exit_to_user_mode+0x72/0x220
>> [836583.959838]  ? srso_alias_return_thunk+0x5/0xfbef5
>> [836583.959842]  ? do_syscall_64+0x8e/0x160
>> [836583.959845]  ? srso_alias_return_thunk+0x5/0xfbef5
>> [836583.959849]  ? do_syscall_64+0x8e/0x160
>> [836583.959851]  ? srso_alias_return_thunk+0x5/0xfbef5
>> [836583.959855]  ? do_syscall_64+0x8e/0x160
>> [836583.959858]  ? srso_alias_return_thunk+0x5/0xfbef5
>> [836583.959861]  ? do_syscall_64+0x8e/0x160
>> [836583.959864]  ? srso_alias_return_thunk+0x5/0xfbef5
>> [836583.959868]  ? srso_alias_return_thunk+0x5/0xfbef5
>> [836583.959873]  entry_SYSCALL_64_after_hwframe+0x76/0x7e
>> [836583.959878] RIP: 0033:0x7f3e4261af2d
>> [836583.959944] RSP: 002b:00007ffec002f400 EFLAGS: 00000246 ORIG_RAX:
>> 0000000000000010
>> [836583.959950] RAX: ffffffffffffffda RBX: 00007ffec002f570 RCX:
>> 00007f3e4261af2d
>> [836583.959952] RDX: 00007ffec002f470 RSI: 00000000c0185879 RDI:
>> 0000000000000003
>> [836583.959955] RBP: 00007ffec002f450 R08: 0000562d74da7010 R09:
>> 00007ffec002e7f2
>> [836583.959957] R10: 0000000000000000 R11: 0000000000000246 R12:
>> 0000562d74daafc0
>> [836583.959960] R13: 0000000000000003 R14: 0000562d74daa970 R15:
>> 0000562d74daad40
>> [836583.959967]  </TASK>
>> ---
>>   fs/btrfs/extent-tree.c | 20 ++++++++++++++++----
>>   1 file changed, 16 insertions(+), 4 deletions(-)
>>
>> diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
>> index feec49e6f9c8..7e4c1d4f2f7c 100644
>> --- a/fs/btrfs/extent-tree.c
>> +++ b/fs/btrfs/extent-tree.c
>> @@ -16,6 +16,7 @@
>>   #include <linux/percpu_counter.h>
>>   #include <linux/lockdep.h>
>>   #include <linux/crc32c.h>
>> +#include <linux/freezer.h>
>>   #include "ctree.h"
>>   #include "extent-tree.h"
>>   #include "transaction.h"
>> @@ -6361,6 +6362,11 @@ void btrfs_error_unpin_extent_range(struct
>> btrfs_fs_info *fs_info, u64 start, u6
>>       unpin_extent_range(fs_info, start, end, false);
>>   }
>> +static bool btrfs_trim_interrupted(void)
>> +{
>> +    return fatal_signal_pending(current) || freezing(current);
>> +}
>> +
>>   /*
>>    * It used to be that old block groups would be left around forever.
>>    * Iterating over them would be enough to trim unused space.  Since we
>> @@ -6459,8 +6465,8 @@ static int btrfs_trim_free_extents(struct
>> btrfs_device *device, u64 *trimmed)
>>           start += len;
>>           *trimmed += bytes;
>> -        if (fatal_signal_pending(current)) {
>> -            ret = -ERESTARTSYS;
>> +        if (btrfs_trim_interrupted()) {
>> +            ret = 0;
>>               break;

Here we should still return the same error number other than 0, to let
the caller know the operation is interrupted, other than finished normally.

>>           }
>> @@ -6508,6 +6514,9 @@ int btrfs_trim_fs(struct btrfs_fs_info *fs_info,
>> struct fstrim_range *range)
>>       cache = btrfs_lookup_first_block_group(fs_info, range->start);
>>       for (; cache; cache = btrfs_next_block_group(cache)) {
>> +        if (btrfs_trim_interrupted())
>> +            break;
>> +

The same here.

>>           if (cache->start >= range_end) {
>>               btrfs_put_block_group(cache);
>>               break;
>> @@ -6547,17 +6556,20 @@ int btrfs_trim_fs(struct btrfs_fs_info
>> *fs_info, struct fstrim_range *range)
>>       mutex_lock(&fs_devices->device_list_mutex);
>>       list_for_each_entry(device, &fs_devices->devices, dev_list) {
>> +        if (btrfs_trim_interrupted())
>> +            break;
>> +

The same here.

Furthermore, I think we may not need the extra checks.

The fstrim is based on block groups, and a block group is normally 1GiB,
at most 10GiB (for RAID0/5/6/10 only), thus exiting at each block group
boundary should be enough to meet the hibernation/suspension timeout.



>>           if (test_bit(BTRFS_DEV_STATE_MISSING, &device->dev_state))
>>               continue;
>>           ret = btrfs_trim_free_extents(device, &group_trimmed);
>> +
>> +        trimmed += group_trimmed;
>>           if (ret) {
>>               dev_failed++;
>>               dev_ret = ret;
>>               break;
>>           }
>> -
>> -        trimmed += group_trimmed;

Any special reason moving the code here?

Thanks,
Qu

>>       }
>>       mutex_unlock(&fs_devices->device_list_mutex);
>

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