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iomap: make buffered writes work with RWF_DONTCACHE

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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: "Darrick J. Wong" <djwong@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Link: https://lore.kernel.org/r/20250204184047.356762-2-axboe@kernel.dk
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christian Brauner <brauner@kernel.org>
This commit is contained in:
Jens Axboe 2025-02-04 11:39:59 -07:00 committed by Christian Brauner
parent 2014c95afe
commit b2cd5ae693
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GPG key ID: 91C61BC06578DCA2
4 changed files with 12 additions and 0 deletions
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5
Documentation/filesystems/iomap/design.rst
View file

@ -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

2
Documentation/filesystems/iomap/operations.rst
View file

@ -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
------------------------

4
fs/iomap/buffered-io.c
View file

@ -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);

1
include/linux/iomap.h
View file

@ -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 {
/*