Unverified Commit c5690dd0 authored by Christoph Hellwig's avatar Christoph Hellwig Committed by Christian Brauner
Browse files

iomap: add read_folio_range() handler for buffered writes 



Add a read_folio_range() handler for buffered writes that filesystems
may pass in if they wish to provide a custom handler for synchronously
reading in the contents of a folio.

Signed-off-by: default avatarJoanne Koong <joannelkoong@gmail.com>
[hch: renamed to read_folio_range, pass less arguments]
Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/20250710133343.399917-14-hch@lst.de


Reviewed-by: default avatarDarrick J. Wong <djwong@kernel.org>
Signed-off-by: default avatarChristian Brauner <brauner@kernel.org>
parent e6caf01d

Documentation/filesystems/iomap/operations.rst

+6 −0
Original line number Diff line number Diff line
@@ -68,6 +68,8 @@ The following address space operations can be wrapped easily: 
     void (*put_folio)(struct inode *inode, loff_t pos, unsigned copied,

                       struct folio *folio);

     bool (*iomap_valid)(struct inode *inode, const struct iomap *iomap);

     int (*read_folio_range)(const struct iomap_iter *iter,

     			struct folio *folio, loff_t pos, size_t len);

 };



iomap calls these functions:
@@ -123,6 +125,10 @@ iomap calls these functions: 
    ``->iomap_valid``, then the iomap should considered stale and the

    validation failed.



  - ``read_folio_range``: Called to synchronously read in the range that will

    be written to. If this function is not provided, iomap will default to

    submitting a bio read request.



These ``struct kiocb`` flags are significant for buffered I/O with iomap:



 * ``IOCB_NOWAIT``: Turns on ``IOMAP_NOWAIT``.

fs/iomap/buffered-io.c

+9 −4
Original line number Diff line number Diff line
@@ -671,7 +671,8 @@ static int iomap_read_folio_range(const struct iomap_iter *iter, 
	return submit_bio_wait(&bio);

}



static int __iomap_write_begin(const struct iomap_iter *iter, size_t len,

static int __iomap_write_begin(const struct iomap_iter *iter,

		const struct iomap_write_ops *write_ops, size_t len,

		struct folio *folio)

{

	struct iomap_folio_state *ifs;
@@ -722,8 +723,12 @@ static int __iomap_write_begin(const struct iomap_iter *iter, size_t len, 
			if (iter->flags & IOMAP_NOWAIT)

				return -EAGAIN;



			status = iomap_read_folio_range(iter, folio,

					block_start, plen);

			if (write_ops && write_ops->read_folio_range)

				status = write_ops->read_folio_range(iter,

						folio, block_start, plen);

			else

				status = iomap_read_folio_range(iter,

						folio, block_start, plen);

			if (status)

				return status;

		}
@@ -839,7 +844,7 @@ static int iomap_write_begin(struct iomap_iter *iter, 
	else if (srcmap->flags & IOMAP_F_BUFFER_HEAD)

		status = __block_write_begin_int(folio, pos, len, NULL, srcmap);

	else

		status = __iomap_write_begin(iter, len, folio);

		status = __iomap_write_begin(iter, write_ops, len, folio);



	if (unlikely(status))

		goto out_unlock;

include/linux/iomap.h

+10 −0
Original line number Diff line number Diff line
@@ -166,6 +166,16 @@ struct iomap_write_ops { 
	 * locked by the iomap code.

	 */

	bool (*iomap_valid)(struct inode *inode, const struct iomap *iomap);



	/*

	 * Optional if the filesystem wishes to provide a custom handler for

	 * reading in the contents of a folio, otherwise iomap will default to

	 * submitting a bio read request.

	 *

	 * The read must be done synchronously.

	 */

	int (*read_folio_range)(const struct iomap_iter *iter,

			struct folio *folio, loff_t pos, size_t len);

};



/*