Make statx() support reporting direct I/O (DIO) alignment information.
This provides a generic interface for userspace programs to determine
whether a file supports DIO, and if so with what alignment restrictions.
Specifically, STATX_DIOALIGN works on block devices, and on regular
files when their containing filesystem has implemented support.
An interface like this has been requested for years, since the
conditions for when DIO is supported in Linux have gotten increasingly
complex over time. Today, DIO support and alignment requirements can be
affected by various filesystem features such as multi-device support,
data journalling, inline data, encryption, verity, compression,
checkpoint disabling, log-structured mode, etc. Further complicating
things, Linux v6.0 relaxed the traditional rule of DIO needing to be
aligned to the block device's logical block size; now user buffers (but
not file offsets) only need to be aligned to the DMA alignment.
The approach of uplifting the XFS specific ioctl XFS_IOC_DIOINFO was
discarded in favor of creating a clean new interface with statx().
For more information, see the individual commits and the man page update
https://lore.kernel.org/r/20220722074229.148925-1-ebiggers@kernel.org.
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Merge tag 'statx-dioalign-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiggers/linux
Pull STATX_DIOALIGN support from Eric Biggers:
"Make statx() support reporting direct I/O (DIO) alignment information.
This provides a generic interface for userspace programs to determine
whether a file supports DIO, and if so with what alignment
restrictions. Specifically, STATX_DIOALIGN works on block devices, and
on regular files when their containing filesystem has implemented
support.
An interface like this has been requested for years, since the
conditions for when DIO is supported in Linux have gotten increasingly
complex over time. Today, DIO support and alignment requirements can
be affected by various filesystem features such as multi-device
support, data journalling, inline data, encryption, verity,
compression, checkpoint disabling, log-structured mode, etc.
Further complicating things, Linux v6.0 relaxed the traditional rule
of DIO needing to be aligned to the block device's logical block size;
now user buffers (but not file offsets) only need to be aligned to the
DMA alignment.
The approach of uplifting the XFS specific ioctl XFS_IOC_DIOINFO was
discarded in favor of creating a clean new interface with statx().
For more information, see the individual commits and the man page
update[1]"
Link: https://lore.kernel.org/r/20220722074229.148925-1-ebiggers@kernel.org [1]
* tag 'statx-dioalign-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiggers/linux:
xfs: support STATX_DIOALIGN
f2fs: support STATX_DIOALIGN
f2fs: simplify f2fs_force_buffered_io()
f2fs: move f2fs_force_buffered_io() into file.c
ext4: support STATX_DIOALIGN
fscrypt: change fscrypt_dio_supported() to prepare for STATX_DIOALIGN
vfs: support STATX_DIOALIGN on block devices
statx: add direct I/O alignment information
725737e7c2