Unverified Commit 034c29fb authored by Christoph Hellwig's avatar Christoph Hellwig Committed by Christian Brauner
Browse files

iomap: add a IOMAP_F_ANON_WRITE flag 



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: default avatarChristoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20250206064035.2323428-4-hch@lst.de


Reviewed-by: default avatar"Darrick J. Wong" <djwong@kernel.org>
Signed-off-by: default avatarChristian Brauner <brauner@kernel.org>
parent 71027333

Documentation/filesystems/iomap/design.rst

+4 −0
Original line number Diff line number Diff line
@@ -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:

fs/iomap/buffered-io.c

+9 −4
Original line number Diff line number Diff line
@@ -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)

	} 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;

	/*

fs/iomap/direct-io.c

+4 −2
Original line number Diff line number Diff line
@@ -81,11 +81,13 @@ 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)

{

include/linux/iomap.h

+7 −0
Original line number Diff line number Diff line
@@ -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;

}