[PATCH v4 0/9] make statx() return DIO alignment information

Eric Biggers
2022-07-22T07:15:04Z

This patchset makes the statx() system call return direct I/O (DIO)
alignment information. This allows userspace to easily determine
whether a file supports DIO, and if so with what alignment restrictions.

Patch 1 adds the basic VFS support for STATX_DIOALIGN. Patch 2 wires it
up for all block device files. The remaining patches wire it up for
regular files on ext4, f2fs, and xfs. Support for regular files on
other filesystems can be added later.

I've also written a man-pages patch, which I'm sending separately.

Note, f2fs has one corner case where DIO reads are allowed but not DIO
writes. The proposed statx fields can't represent this. My proposal
(patch 6) is to just eliminate this case, as it seems much too weird.
But I'd appreciate any feedback on that part.

This patchset applies to v5.19-rc7.

Changed v3 => v4:
- Added xfs support.

- Moved the helper function for block devices into block/bdev.c.

- Adjusted the ext4 patch to not introduce a bug where misaligned DIO
starts being allowed on encrypted files when it gets combined with
the patch "iomap: add support for dma aligned direct-io" that is
queued in the block tree for 5.20.

- Made a simplification in fscrypt_dio_supported().

Changed v2 => v3:
- Dropped the stx_offset_align_optimal field, since its purpose
wasn't clearly distinguished from the existing stx_blksize.

- Renamed STATX_IOALIGN to STATX_DIOALIGN, to reflect the new focus
on DIO only.

- Similarly, renamed stx_{mem,offset}_align_dio to
stx_dio_{mem,offset}_align, to reflect the new focus on DIO only.

- Wired up STATX_DIOALIGN on block device files.

Changed v1 => v2:
- No changes.

Eric Biggers (9):
statx: add direct I/O alignment information
vfs: support STATX_DIOALIGN on block devices
fscrypt: change fscrypt_dio_supported() to prepare for STATX_DIOALIGN
ext4: support STATX_DIOALIGN
f2fs: move f2fs_force_buffered_io() into file.c
f2fs: don't allow DIO reads but not DIO writes
f2fs: simplify f2fs_force_buffered_io()
f2fs: support STATX_DIOALIGN
xfs: support STATX_DIOALIGN

block/bdev.c | 25 ++++++++++++++++++++
fs/crypto/inline_crypt.c | 49 +++++++++++++++++++--------------------
fs/ext4/ext4.h | 1 +
fs/ext4/file.c | 37 ++++++++++++++++++++---------
fs/ext4/inode.c | 36 ++++++++++++++++++++++++++++
fs/f2fs/f2fs.h | 45 -----------------------------------
fs/f2fs/file.c | 45 ++++++++++++++++++++++++++++++++++-
fs/stat.c | 14 +++++++++++
fs/xfs/xfs_iops.c | 9 +++++++
include/linux/blkdev.h | 4 ++++
include/linux/fscrypt.h | 7 ++----
include/linux/stat.h | 2 ++
include/uapi/linux/stat.h | 4 +++-
13 files changed, 190 insertions(+), 88 deletions(-)

base-commit: ff6992735ade75aae3e35d16b17da1008d753d28
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2.37.0