On Thu 06-04-23 23:06:21, Chao Yu wrote:
> 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/[email protected]/
> Suggested-by: Theodore Ts'o <[email protected]>
> Signed-off-by: Chao Yu <[email protected]>
Looks good to me. Feel free to add:
Reviewed-by: Jan Kara <[email protected]>
Honza
> ---
> 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
>
--
Jan Kara <[email protected]>
SUSE Labs, CR
Ping,
On 2023/4/21 17:35, Jan Kara wrote:
> On Thu 06-04-23 23:06:21, Chao Yu wrote:
>> 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/[email protected]/
>> Suggested-by: Theodore Ts'o <[email protected]>
>> Signed-off-by: Chao Yu <[email protected]>
>
> Looks good to me. Feel free to add:
>
> Reviewed-by: Jan Kara <[email protected]>
>
> Honza
>
>> ---
>> 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
>>