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iomap: add a IOMAP_DIO_OVERWRITE_ONLY flag 

Add a flag to signal that only pure overwrites are allowed.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
This commit is contained in:
Christoph Hellwig 2021-01-23 10:06:10 -08:00 committed by Darrick J. Wong
parent 2f63296578
commit 213f627104
2 changed files with 15 additions and 0 deletions
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7
fs/iomap/direct-io.c
View File

@ -485,6 +485,13 @@ __iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
iomap_flags |= IOMAP_NOWAIT;
}
if (dio_flags & IOMAP_DIO_OVERWRITE_ONLY) {
ret = -EAGAIN;
if (pos >= dio->i_size || pos + count > dio->i_size)
goto out_free_dio;
iomap_flags |= IOMAP_OVERWRITE_ONLY;
}
ret = filemap_write_and_wait_range(mapping, pos, end);
if (ret)
goto out_free_dio;

8
include/linux/iomap.h
View File

@ -122,6 +122,7 @@ struct iomap_page_ops {
#define IOMAP_FAULT (1 << 3) /* mapping for page fault */
#define IOMAP_DIRECT (1 << 4) /* direct I/O */
#define IOMAP_NOWAIT (1 << 5) /* do not block */
#define IOMAP_OVERWRITE_ONLY (1 << 6) /* only pure overwrites allowed */
struct iomap_ops {
/*
@ -262,6 +263,13 @@ struct iomap_dio_ops {
*/
#define IOMAP_DIO_FORCE_WAIT (1 << 0)
/*
* Do not allocate blocks or zero partial blocks, but instead fall back to
* the caller by returning -EAGAIN. Used to optimize direct I/O writes that
* are not aligned to the file system block size.
*/
#define IOMAP_DIO_OVERWRITE_ONLY (1 << 1)
ssize_t iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
const struct iomap_ops *ops, const struct iomap_dio_ops *dops,
unsigned int dio_flags);