| Message ID | 20250106151607.954940-3-hch@lst.de (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | [1/4] fs: reformat the statx definition | expand |
On Mon 06-01-25 16:15:55, Christoph Hellwig wrote: > Add a separate dio read align field, as many out of place write > file systems can easily do reads aligned to the device sector size, > but require bigger alignment for writes. > > This is usually papered over by falling back to buffered I/O for smaller > writes and doing read-modify-write cycles, but performance for this > sucks, so applications benefit from knowing the actual write alignment. > > Signed-off-by: Christoph Hellwig <hch@lst.de> > Reviewed-by: Darrick J. Wong <djwong@kernel.org> So if I understand right dio_offset_align is guaranteed to work for all DIO (i.e., maximum of all possible alignments), dio_read_offset_align is possibly lower and works only for reads. Looks good to me. Feel free to add: Reviewed-by: Jan Kara <jack@suse.cz> Honza > --- > fs/stat.c | 1 + > include/linux/stat.h | 1 + > include/uapi/linux/stat.h | 4 +++- > 3 files changed, 5 insertions(+), 1 deletion(-) > > diff --git a/fs/stat.c b/fs/stat.c > index 0870e969a8a0..2c0e111a098a 100644 > --- a/fs/stat.c > +++ b/fs/stat.c > @@ -725,6 +725,7 @@ cp_statx(const struct kstat *stat, struct statx __user *buffer) > tmp.stx_mnt_id = stat->mnt_id; > tmp.stx_dio_mem_align = stat->dio_mem_align; > tmp.stx_dio_offset_align = stat->dio_offset_align; > + tmp.stx_dio_read_offset_align = stat->dio_read_offset_align; > tmp.stx_subvol = stat->subvol; > tmp.stx_atomic_write_unit_min = stat->atomic_write_unit_min; > tmp.stx_atomic_write_unit_max = stat->atomic_write_unit_max; > diff --git a/include/linux/stat.h b/include/linux/stat.h > index 3d900c86981c..9d8382e23a9c 100644 > --- a/include/linux/stat.h > +++ b/include/linux/stat.h > @@ -52,6 +52,7 @@ struct kstat { > u64 mnt_id; > u32 dio_mem_align; > u32 dio_offset_align; > + u32 dio_read_offset_align; > u64 change_cookie; > u64 subvol; > u32 atomic_write_unit_min; > diff --git a/include/uapi/linux/stat.h b/include/uapi/linux/stat.h > index 8b35d7d511a2..f78ee3670dd5 100644 > --- a/include/uapi/linux/stat.h > +++ b/include/uapi/linux/stat.h > @@ -179,7 +179,8 @@ struct statx { > /* Max atomic write segment count */ > __u32 stx_atomic_write_segments_max; > > - __u32 __spare1[1]; > + /* File offset alignment for direct I/O reads */ > + __u32 stx_dio_read_offset_align; > > /* 0xb8 */ > __u64 __spare3[9]; /* Spare space for future expansion */ > @@ -213,6 +214,7 @@ struct statx { > #define STATX_MNT_ID_UNIQUE 0x00004000U /* Want/got extended stx_mount_id */ > #define STATX_SUBVOL 0x00008000U /* Want/got stx_subvol */ > #define STATX_WRITE_ATOMIC 0x00010000U /* Want/got atomic_write_* fields */ > +#define STATX_DIO_READ_ALIGN 0x00020000U /* Want/got dio read alignment info */ > > #define STATX__RESERVED 0x80000000U /* Reserved for future struct statx expansion */ > > -- > 2.45.2 >
On Mon, Jan 06, 2025 at 05:32:14PM +0100, Jan Kara wrote: > > Add a separate dio read align field, as many out of place write > > file systems can easily do reads aligned to the device sector size, > > but require bigger alignment for writes. > > > > This is usually papered over by falling back to buffered I/O for smaller > > writes and doing read-modify-write cycles, but performance for this > > sucks, so applications benefit from knowing the actual write alignment. > > > > Signed-off-by: Christoph Hellwig <hch@lst.de> > > Reviewed-by: Darrick J. Wong <djwong@kernel.org> > > So if I understand right dio_offset_align is guaranteed to work for all DIO > (i.e., maximum of all possible alignments), dio_read_offset_align is > possibly lower and works only for reads. Yes. If you think this needs to be made more clear I'm open to suggestions to improve the wording.
diff --git a/fs/stat.c b/fs/stat.c index 0870e969a8a0..2c0e111a098a 100644 --- a/fs/stat.c +++ b/fs/stat.c @@ -725,6 +725,7 @@ cp_statx(const struct kstat *stat, struct statx __user *buffer) tmp.stx_mnt_id = stat->mnt_id; tmp.stx_dio_mem_align = stat->dio_mem_align; tmp.stx_dio_offset_align = stat->dio_offset_align; + tmp.stx_dio_read_offset_align = stat->dio_read_offset_align; tmp.stx_subvol = stat->subvol; tmp.stx_atomic_write_unit_min = stat->atomic_write_unit_min; tmp.stx_atomic_write_unit_max = stat->atomic_write_unit_max; diff --git a/include/linux/stat.h b/include/linux/stat.h index 3d900c86981c..9d8382e23a9c 100644 --- a/include/linux/stat.h +++ b/include/linux/stat.h @@ -52,6 +52,7 @@ struct kstat { u64 mnt_id; u32 dio_mem_align; u32 dio_offset_align; + u32 dio_read_offset_align; u64 change_cookie; u64 subvol; u32 atomic_write_unit_min; diff --git a/include/uapi/linux/stat.h b/include/uapi/linux/stat.h index 8b35d7d511a2..f78ee3670dd5 100644 --- a/include/uapi/linux/stat.h +++ b/include/uapi/linux/stat.h @@ -179,7 +179,8 @@ struct statx { /* Max atomic write segment count */ __u32 stx_atomic_write_segments_max; - __u32 __spare1[1]; + /* File offset alignment for direct I/O reads */ + __u32 stx_dio_read_offset_align; /* 0xb8 */ __u64 __spare3[9]; /* Spare space for future expansion */ @@ -213,6 +214,7 @@ struct statx { #define STATX_MNT_ID_UNIQUE 0x00004000U /* Want/got extended stx_mount_id */ #define STATX_SUBVOL 0x00008000U /* Want/got stx_subvol */ #define STATX_WRITE_ATOMIC 0x00010000U /* Want/got atomic_write_* fields */ +#define STATX_DIO_READ_ALIGN 0x00020000U /* Want/got dio read alignment info */ #define STATX__RESERVED 0x80000000U /* Reserved for future struct statx expansion */