Unverified Commit b2cd5ae6 authored by Jens Axboe's avatar Jens Axboe Committed by Christian Brauner
Browse files

iomap: make buffered writes work with RWF_DONTCACHE 



Add iomap buffered write support for RWF_DONTCACHE. If RWF_DONTCACHE is
set for a write, mark the folios being written as uncached. Then
writeback completion will drop the pages. The write_iter handler simply
kicks off writeback for the pages, and writeback completion will take
care of the rest.

Signed-off-by: default avatar"Darrick J. Wong" <djwong@kernel.org>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
Link: https://lore.kernel.org/r/20250204184047.356762-2-axboe@kernel.dk


Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarChristian Brauner <brauner@kernel.org>
parent 2014c95a

Documentation/filesystems/iomap/design.rst

+5 −0
Original line number Diff line number Diff line
@@ -352,6 +352,11 @@ operations: 
   ``IOMAP_NOWAIT`` is often set on behalf of ``IOCB_NOWAIT`` or

   ``RWF_NOWAIT``.



 * ``IOMAP_DONTCACHE`` is set when the caller wishes to perform a

   buffered file I/O and would like the kernel to drop the pagecache

   after the I/O completes, if it isn't already being used by another

   thread.



If it is necessary to read existing file contents from a `different

<https://lore.kernel.org/all/20191008071527.29304-9-hch@lst.de/>`_

device or address range on a device, the filesystem should return that

Documentation/filesystems/iomap/operations.rst

+2 −0
Original line number Diff line number Diff line
@@ -131,6 +131,8 @@ These ``struct kiocb`` flags are significant for buffered I/O with iomap: 


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



 * ``IOCB_DONTCACHE``: Turns on ``IOMAP_DONTCACHE``.



Internal per-Folio State

------------------------

fs/iomap/buffered-io.c

+4 −0
Original line number Diff line number Diff line
@@ -603,6 +603,8 @@ struct folio *iomap_get_folio(struct iomap_iter *iter, loff_t pos, size_t len) 


	if (iter->flags & IOMAP_NOWAIT)

		fgp |= FGP_NOWAIT;

	if (iter->flags & IOMAP_DONTCACHE)

		fgp |= FGP_DONTCACHE;

	fgp |= fgf_set_order(len);



	return __filemap_get_folio(iter->inode->i_mapping, pos >> PAGE_SHIFT,
@@ -1034,6 +1036,8 @@ iomap_file_buffered_write(struct kiocb *iocb, struct iov_iter *i, 


	if (iocb->ki_flags & IOCB_NOWAIT)

		iter.flags |= IOMAP_NOWAIT;

	if (iocb->ki_flags & IOCB_DONTCACHE)

		iter.flags |= IOMAP_DONTCACHE;



	while ((ret = iomap_iter(&iter, ops)) > 0)

		iter.processed = iomap_write_iter(&iter, i);

include/linux/iomap.h

+1 −0
Original line number Diff line number Diff line
@@ -183,6 +183,7 @@ struct iomap_folio_ops { 
#define IOMAP_DAX		0

#endif /* CONFIG_FS_DAX */

#define IOMAP_ATOMIC		(1 << 9)

#define IOMAP_DONTCACHE		(1 << 10)



struct iomap_ops {

	/*