| Message ID | 20230406150621.3854298-1-chao@kernel.org |
|---|---|
| State | New |
| Headers | show |
| Series | ext4: fix wrong calculation of minlen in ext4_trim_fs() | expand |
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/20230311031843.GF860405@mit.edu/ > Suggested-by: Theodore Ts'o <tytso@mit.edu> > Signed-off-by: Chao Yu <chao@kernel.org> Looks good to me. Feel free to add: Reviewed-by: Jan Kara <jack@suse.cz> 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 >
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/20230311031843.GF860405@mit.edu/ >> Suggested-by: Theodore Ts'o <tytso@mit.edu> >> Signed-off-by: Chao Yu <chao@kernel.org> > > Looks good to me. Feel free to add: > > Reviewed-by: Jan Kara <jack@suse.cz> > > 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 >>
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 ||
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@mit.edu/ Suggested-by: Theodore Ts'o <tytso@mit.edu> Signed-off-by: Chao Yu <chao@kernel.org> --- fs/ext4/mballoc.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)