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STATX_DIOALIGN for 6.1

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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
This commit is contained in:
Linus Torvalds 2022-10-03 20:33:41 -07:00
commit 725737e7c2
13 changed files with 188 additions and 83 deletions
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4
include/uapi/linux/stat.h
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@ -124,7 +124,8 @@ struct statx {
__u32 stx_dev_minor;
/* 0x90 */
__u64 stx_mnt_id;
__u64 __spare2;
__u32 stx_dio_mem_align; /* Memory buffer alignment for direct I/O */
__u32 stx_dio_offset_align; /* File offset alignment for direct I/O */
/* 0xa0 */
__u64 __spare3[12]; /* Spare space for future expansion */
/* 0x100 */
@ -152,6 +153,7 @@ struct statx {
#define STATX_BASIC_STATS 0x000007ffU /* The stuff in the normal stat struct */
#define STATX_BTIME 0x00000800U /* Want/got stx_btime */
#define STATX_MNT_ID 0x00001000U /* Got stx_mnt_id */
#define STATX_DIOALIGN 0x00002000U /* Want/got direct I/O alignment info */
#define STATX__RESERVED 0x80000000U /* Reserved for future struct statx expansion */