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825cf206ed
Traditionally, the conditions for when DIO (direct I/O) is supported
were fairly simple. For both block devices and regular files, DIO had
to be aligned to the logical block size of the block device.
However, due to filesystem features that have been added over time (e.g.
multi-device support, data journalling, inline data, encryption, verity,
compression, checkpoint disabling, log-structured mode), the conditions
for when DIO is allowed on a regular file have gotten increasingly
complex. Whether a particular regular file supports DIO, and with what
alignment, can depend on various file attributes and filesystem mount
options, as well as which block device(s) the file's data is located on.
Moreover, the general rule of DIO needing to be aligned to the block
device's logical block size was recently relaxed to allow user buffers
(but not file offsets) aligned to the DMA alignment instead. See
commit bf8d08532b ("iomap: add support for dma aligned direct-io").
XFS has an ioctl XFS_IOC_DIOINFO that exposes DIO alignment information.
Uplifting this to the VFS is one possibility. However, as discussed
(https://lore.kernel.org/linux-fsdevel/20220120071215.123274-1-ebiggers@kernel.org/T/#u),
this ioctl is rarely used and not known to be used outside of
XFS-specific code. It was also never intended to indicate when a file
doesn't support DIO at all, nor was it intended for block devices.
Therefore, let's expose this information via statx(). Add the
STATX_DIOALIGN flag and two new statx fields associated with it:
* stx_dio_mem_align: the alignment (in bytes) required for user memory
buffers for DIO, or 0 if DIO is not supported on the file.
* stx_dio_offset_align: the alignment (in bytes) required for file
offsets and I/O segment lengths for DIO, or 0 if DIO is not supported
on the file. This will only be nonzero if stx_dio_mem_align is
nonzero, and vice versa.
Note that as with other statx() extensions, if STATX_DIOALIGN isn't set
in the returned statx struct, then these new fields won't be filled in.
This will happen if the file is neither a regular file nor a block
device, or if the file is a regular file and the filesystem doesn't
support STATX_DIOALIGN. It might also happen if the caller didn't
include STATX_DIOALIGN in the request mask, since statx() isn't required
to return unrequested information.
This commit only adds the VFS-level plumbing for STATX_DIOALIGN. For
regular files, individual filesystems will still need to add code to
support it. For block devices, a separate commit will wire it up too.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Reviewed-by: Christian Brauner (Microsoft) <brauner@kernel.org>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Link: https://lore.kernel.org/r/20220827065851.135710-2-ebiggers@kernel.org
57 lines
1.4 KiB
C
57 lines
1.4 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _LINUX_STAT_H
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#define _LINUX_STAT_H
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#include <asm/stat.h>
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#include <uapi/linux/stat.h>
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#define S_IRWXUGO (S_IRWXU|S_IRWXG|S_IRWXO)
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#define S_IALLUGO (S_ISUID|S_ISGID|S_ISVTX|S_IRWXUGO)
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#define S_IRUGO (S_IRUSR|S_IRGRP|S_IROTH)
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#define S_IWUGO (S_IWUSR|S_IWGRP|S_IWOTH)
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#define S_IXUGO (S_IXUSR|S_IXGRP|S_IXOTH)
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#define UTIME_NOW ((1l << 30) - 1l)
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#define UTIME_OMIT ((1l << 30) - 2l)
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#include <linux/types.h>
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#include <linux/time.h>
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#include <linux/uidgid.h>
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struct kstat {
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u32 result_mask; /* What fields the user got */
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umode_t mode;
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unsigned int nlink;
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uint32_t blksize; /* Preferred I/O size */
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u64 attributes;
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u64 attributes_mask;
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#define KSTAT_ATTR_FS_IOC_FLAGS \
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(STATX_ATTR_COMPRESSED | \
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STATX_ATTR_IMMUTABLE | \
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STATX_ATTR_APPEND | \
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STATX_ATTR_NODUMP | \
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STATX_ATTR_ENCRYPTED | \
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STATX_ATTR_VERITY \
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)/* Attrs corresponding to FS_*_FL flags */
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#define KSTAT_ATTR_VFS_FLAGS \
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(STATX_ATTR_IMMUTABLE | \
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STATX_ATTR_APPEND \
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) /* Attrs corresponding to S_* flags that are enforced by the VFS */
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u64 ino;
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dev_t dev;
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dev_t rdev;
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kuid_t uid;
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kgid_t gid;
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loff_t size;
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struct timespec64 atime;
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struct timespec64 mtime;
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struct timespec64 ctime;
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struct timespec64 btime; /* File creation time */
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u64 blocks;
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u64 mnt_id;
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u32 dio_mem_align;
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u32 dio_offset_align;
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};
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#endif
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