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Message-ID: <20240822164908.4957-1-luca.stefani.ge1@gmail.com>
Date: Thu, 22 Aug 2024 18:48:21 +0200
From: Luca Stefani <luca.stefani.ge1@...il.com>
To: 
Cc: Luca Stefani <luca.stefani.ge1@...il.com>,
	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: [PATCH] btrfs: Don't block system suspend during fstrim

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;
 		}
 
@@ -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;
+
 		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;
+
 		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;
 	}
 	mutex_unlock(&fs_devices->device_list_mutex);
 
-- 
2.46.0


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