linux-kernel - Re: [PATCH v2 3/3] btrfs: Don't block system suspend during fstrim

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Message-ID: <6416ac73-0a2a-4568-b407-62fbeb6d5540@suse.com>
Date: Tue, 3 Sep 2024 08:06:18 +0930
From: Qu Wenruo <wqu@...e.com>
To: Luca Stefani <luca.stefani.ge1@...il.com>
Cc: Jens Axboe <axboe@...nel.dk>, Chris Mason <clm@...com>,
 Josef Bacik <josef@...icpanda.com>, David Sterba <dsterba@...e.com>,
 linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-btrfs@...r.kernel.org
Subject: Re: [PATCH v2 3/3] btrfs: Don't block system suspend during fstrim



在 2024/9/3 06:26, Luca Stefani 写道:
> Sometimes the system isn't able to suspend because the task
> responsible for trimming the device isn't able to finish in
> time, especially since we have a free extent discarding phase,
> which can trim a lot of unallocated space, and there is no
> limits on the trim size (unlike the block group part).
> 
> Since discard isn't a critical call it can be interrupted
> at any time, in such cases we stop the trim, report the amount
> of discarded bytes and return failure.
> 
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=219180
> Link: https://bugzilla.suse.com/show_bug.cgi?id=1229737
> Signed-off-by: Luca Stefani <luca.stefani.ge1@...il.com>
> ---
>   fs/btrfs/extent-tree.c | 17 ++++++++++++++++-
>   1 file changed, 16 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
> index 894684f4f497..7c78ed4044db 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"
> @@ -1235,6 +1236,11 @@ static int remove_extent_backref(struct btrfs_trans_handle *trans,
>   	return ret;
>   }
>   
> +static bool btrfs_trim_interrupted(void)
> +{
> +	return fatal_signal_pending(current) || freezing(current);
> +}
> +
>   static int btrfs_issue_discard(struct block_device *bdev, u64 start, u64 len,
>   			       u64 *discarded_bytes)
>   {
> @@ -1302,6 +1308,9 @@ static int btrfs_issue_discard(struct block_device *bdev, u64 start, u64 len,
>   	}
>   
>   	while (bytes_left) {
> +		if (btrfs_trim_interrupted())
> +			break;
> +

Although with this change, the check should be more than enough to cover 
everything, better than the existing per-block-group check and the 
possibly large discard for the free extents.

Thus just this check would be enough.

The other thing is the old return value, I guess you can just add "ret = 
-EERESTARTSYS;" before the break.

Thanks,
Qu
>   		sector = start >> SECTOR_SHIFT;
>   		nr_sects = bytes_left >> SECTOR_SHIFT;
>   		bio_sects = min(nr_sects, bio_discard_limit(bdev, sector));
> @@ -6470,7 +6479,7 @@ static int btrfs_trim_free_extents(struct btrfs_device *device, u64 *trimmed)
>   		start += len;
>   		*trimmed += bytes;
>   
> -		if (fatal_signal_pending(current)) {
> +		if (btrfs_trim_interrupted()) {
>   			ret = -ERESTARTSYS;
>   			break;
>   		}
> @@ -6519,6 +6528,9 @@ 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;
> @@ -6558,6 +6570,9 @@ 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;
>