As Ted pointed out as below: " However the minlen variable in ext4_trim_fs is in units of *clusters*. And so it gets rounded up two places. The first time is when it is converted into units of a cluster: minlen = EXT4_NUM_B2C(EXT4_SB(sb), range->minlen >> sb->s_blocksize_bits); Oh, and by the way, that first conversion is not correct as currently written in ext4_fs_trim(). It should be minlen = (range->minlen + EXT4_CLUSTER_SIZE(sb) - 1) >> (sb->s_blocksize_bits + EXT4_CLUSTER_BITS(sb)); " The reason is if range->minlen is smaller than block size of ext4, original calculation "range->minlen >> sb->s_blocksize_bits" may return zero, but since EXT4_NUM_B2C() expects a non-zero in-parameter, so it needs to round up range->minlen to cluster size directly as above. Link: https://lore.kernel.org/lkml/20230311031843.GF860405@xxxxxxx/ Suggested-by: Theodore Ts'o <tytso@xxxxxxx> Signed-off-by: Chao Yu <chao@xxxxxxxxxx> --- fs/ext4/mballoc.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c index 5b2ae37a8b80..d8b9d6a83d1e 100644 --- a/fs/ext4/mballoc.c +++ b/fs/ext4/mballoc.c @@ -6478,8 +6478,8 @@ int ext4_trim_fs(struct super_block *sb, struct fstrim_range *range) start = range->start >> sb->s_blocksize_bits; end = start + (range->len >> sb->s_blocksize_bits) - 1; - minlen = EXT4_NUM_B2C(EXT4_SB(sb), - range->minlen >> sb->s_blocksize_bits); + minlen = (range->minlen + EXT4_CLUSTER_SIZE(sb) - 1) >> + (sb->s_blocksize_bits + EXT4_CLUSTER_BITS(sb)); if (minlen > EXT4_CLUSTERS_PER_GROUP(sb) || start >= max_blks || -- 2.25.1
