On Nov 3, 2021, at 8:51 AM, Lukas Czerner <lczerner@xxxxxxxxxx> wrote:
>
> There is no good reason for the s_last_trim_minblks to be atomic. There is
> no data integrity needed and there is no real danger in setting and
> reading it in a racy manner. Change it to be unsigned long, the same type
> as s_clusters_per_group which is the maximum that's allowed.
>
> Signed-off-by: Lukas Czerner <lczerner@xxxxxxxxxx>
> Suggested-by: Andreas Dilger <adilger@xxxxxxxxx>
Reviewed-by: Andreas Dilger <adilger@xxxxxxxxx>
Could also add for reference:
Fixes: 3d56b8d2c74c ("ext4: Speed up FITRIM by recording flags in ext4_group_info")
> ---
> fs/ext4/ext4.h | 2 +-
> fs/ext4/mballoc.c | 4 ++--
> 2 files changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
> index 3825195539d7..92a155401f61 100644
> --- a/fs/ext4/ext4.h
> +++ b/fs/ext4/ext4.h
> @@ -1660,7 +1660,7 @@ struct ext4_sb_info {
> struct task_struct *s_mmp_tsk;
>
> /* record the last minlen when FITRIM is called. */
> - atomic_t s_last_trim_minblks;
> + unsigned long s_last_trim_minblks;
>
> /* Reference to checksum algorithm driver via cryptoapi */
> struct crypto_shash *s_chksum_driver;
> diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
> index 72bfac2d6dce..eda550ec3956 100644
> --- a/fs/ext4/mballoc.c
> +++ b/fs/ext4/mballoc.c
> @@ -6374,7 +6374,7 @@ ext4_trim_all_free(struct super_block *sb, ext4_group_t group,
> ext4_lock_group(sb, group);
>
> if (!EXT4_MB_GRP_WAS_TRIMMED(e4b.bd_info) ||
> - minblocks < atomic_read(&EXT4_SB(sb)->s_last_trim_minblks)) {
> + minblocks < EXT4_SB(sb)->s_last_trim_minblks) {
> ret = ext4_try_to_trim_range(sb, &e4b, start, max, minblocks);
> if (ret >= 0)
> EXT4_MB_GRP_SET_TRIMMED(e4b.bd_info);
> @@ -6475,7 +6475,7 @@ int ext4_trim_fs(struct super_block *sb, struct fstrim_range *range)
> }
>
> if (!ret)
> - atomic_set(&EXT4_SB(sb)->s_last_trim_minblks, minlen);
> + EXT4_SB(sb)->s_last_trim_minblks = minlen;
>
> out:
> range->len = EXT4_C2B(EXT4_SB(sb), trimmed) << sb->s_blocksize_bits;
> --
> 2.31.1
>
Cheers, Andreas
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