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iomap: add a IOMAP_F_ANON_WRITE flag

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Add a IOMAP_F_ANON_WRITE flag that indicates that the write I/O does not
have a target block assigned to it yet at iomap time and the file system
will do that in the bio submission handler, splitting the I/O as needed.

This is used to implement Zone Append based I/O for zoned XFS, where
splitting writes to the hardware limits and assigning a zone to them
happens just before sending the I/O off to the block layer, but could
also be useful for other things like compressed I/O.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20250206064035.2323428-4-hch@lst.de
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>
This commit is contained in:
Christoph Hellwig
2025-02-06 07:40:01 +01:00
committed by Christian Brauner
parent 7102733306
commit 034c29fb3e
4 changed files with 24 additions and 6 deletions
Download Patch File Download Diff File Expand all files Collapse all files

4
Documentation/filesystems/iomap/design.rst
View File

@@ -246,6 +246,10 @@ The fields are as follows:
* **IOMAP_F_PRIVATE**: Starting with this value, the upper bits can
be set by the filesystem for its own purposes.
* **IOMAP_F_ANON_WRITE**: Indicates that (write) I/O does not have a target
block assigned to it yet and the file system will do that in the bio
submission handler, splitting the I/O as needed.
These flags can be set by iomap itself during file operations.
The filesystem should supply an ``->iomap_end`` function if it needs
to observe these flags:

13
fs/iomap/buffered-io.c
View File

@@ -1691,10 +1691,14 @@ static int iomap_submit_ioend(struct iomap_writepage_ctx *wpc, int error)
* failure happened so that the file system end I/O handler gets called
* to clean up.
*/
if (wpc->ops->submit_ioend)
if (wpc->ops->submit_ioend) {
error = wpc->ops->submit_ioend(wpc, error);
else if (!error)
submit_bio(&wpc->ioend->io_bio);
} else {
if (WARN_ON_ONCE(wpc->iomap.flags & IOMAP_F_ANON_WRITE))
error = -EIO;
if (!error)
submit_bio(&wpc->ioend->io_bio);
}
if (error) {
wpc->ioend->io_bio.bi_status = errno_to_blk_status(error);
@@ -1744,7 +1748,8 @@ static bool iomap_can_add_to_ioend(struct iomap_writepage_ctx *wpc, loff_t pos,
return false;
if (pos != wpc->ioend->io_offset + wpc->ioend->io_size)
return false;
if (iomap_sector(&wpc->iomap, pos) !=
if (!(wpc->iomap.flags & IOMAP_F_ANON_WRITE) &&
iomap_sector(&wpc->iomap, pos) !=
bio_end_sector(&wpc->ioend->io_bio))
return false;
/*

6
fs/iomap/direct-io.c
View File

@@ -81,10 +81,12 @@ static void iomap_dio_submit_bio(const struct iomap_iter *iter,
WRITE_ONCE(iocb->private, bio);
}
if (dio->dops && dio->dops->submit_io)
if (dio->dops && dio->dops->submit_io) {
dio->dops->submit_io(iter, bio, pos);
else
} else {
WARN_ON_ONCE(iter->iomap.flags & IOMAP_F_ANON_WRITE);
submit_bio(bio);
}
}
ssize_t iomap_dio_complete(struct iomap_dio *dio)

7
include/linux/iomap.h
View File

@@ -56,6 +56,10 @@ struct vm_fault;
*
* IOMAP_F_BOUNDARY indicates that I/O and I/O completions for this iomap must
* never be merged with the mapping before it.
*
* IOMAP_F_ANON_WRITE indicates that (write) I/O does not have a target block
* assigned to it yet and the file system will do that in the bio submission
* handler, splitting the I/O as needed.
*/
#define IOMAP_F_NEW (1U << 0)
#define IOMAP_F_DIRTY (1U << 1)
@@ -68,6 +72,7 @@ struct vm_fault;
#endif /* CONFIG_BUFFER_HEAD */
#define IOMAP_F_XATTR (1U << 5)
#define IOMAP_F_BOUNDARY (1U << 6)
#define IOMAP_F_ANON_WRITE (1U << 7)
/*
* Flags set by the core iomap code during operations:
@@ -111,6 +116,8 @@ struct iomap {
static inline sector_t iomap_sector(const struct iomap *iomap, loff_t pos)
{
if (iomap->flags & IOMAP_F_ANON_WRITE)
return U64_MAX; /* invalid */
return (iomap->addr + pos - iomap->offset) >> SECTOR_SHIFT;
}