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netfs: Provide netfs_file_read_iter()

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Provide a top-level-ish function that can be pointed to directly by
->read_iter file op.

Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
cc: linux-cachefs@redhat.com
cc: linux-fsdevel@vger.kernel.org
cc: linux-mm@kvack.org
This commit is contained in:
David Howells 2023-10-11 09:29:43 +01:00
parent 102a7e2c59
commit 80645bd4aa
2 changed files with 75 additions and 0 deletions
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73
fs/netfs/buffered_read.c
View File

@ -558,3 +558,76 @@ error:
_leave(" = %d", ret);
return ret;
}
/**
* netfs_buffered_read_iter - Filesystem buffered I/O read routine
* @iocb: kernel I/O control block
* @iter: destination for the data read
*
* This is the ->read_iter() routine for all filesystems that can use the page
* cache directly.
*
* The IOCB_NOWAIT flag in iocb->ki_flags indicates that -EAGAIN shall be
* returned when no data can be read without waiting for I/O requests to
* complete; it doesn't prevent readahead.
*
* The IOCB_NOIO flag in iocb->ki_flags indicates that no new I/O requests
* shall be made for the read or for readahead. When no data can be read,
* -EAGAIN shall be returned. When readahead would be triggered, a partial,
* possibly empty read shall be returned.
*
* Return:
* * number of bytes copied, even for partial reads
* * negative error code (or 0 if IOCB_NOIO) if nothing was read
*/
ssize_t netfs_buffered_read_iter(struct kiocb *iocb, struct iov_iter *iter)
{
struct inode *inode = file_inode(iocb->ki_filp);
struct netfs_inode *ictx = netfs_inode(inode);
ssize_t ret;
if (WARN_ON_ONCE((iocb->ki_flags & IOCB_DIRECT) ||
test_bit(NETFS_ICTX_UNBUFFERED, &ictx->flags)))
return -EINVAL;
ret = netfs_start_io_read(inode);
if (ret == 0) {
ret = filemap_read(iocb, iter, 0);
netfs_end_io_read(inode);
}
return ret;
}
EXPORT_SYMBOL(netfs_buffered_read_iter);
/**
* netfs_file_read_iter - Generic filesystem read routine
* @iocb: kernel I/O control block
* @iter: destination for the data read
*
* This is the ->read_iter() routine for all filesystems that can use the page
* cache directly.
*
* The IOCB_NOWAIT flag in iocb->ki_flags indicates that -EAGAIN shall be
* returned when no data can be read without waiting for I/O requests to
* complete; it doesn't prevent readahead.
*
* The IOCB_NOIO flag in iocb->ki_flags indicates that no new I/O requests
* shall be made for the read or for readahead. When no data can be read,
* -EAGAIN shall be returned. When readahead would be triggered, a partial,
* possibly empty read shall be returned.
*
* Return:
* * number of bytes copied, even for partial reads
* * negative error code (or 0 if IOCB_NOIO) if nothing was read
*/
ssize_t netfs_file_read_iter(struct kiocb *iocb, struct iov_iter *iter)
{
struct netfs_inode *ictx = netfs_inode(iocb->ki_filp->f_mapping->host);
if ((iocb->ki_flags & IOCB_DIRECT) ||
test_bit(NETFS_ICTX_UNBUFFERED, &ictx->flags))
return netfs_unbuffered_read_iter(iocb, iter);
return netfs_buffered_read_iter(iocb, iter);
}
EXPORT_SYMBOL(netfs_file_read_iter);

2
include/linux/netfs.h
View File

@ -378,6 +378,8 @@ struct netfs_cache_ops {
/* High-level read API. */
ssize_t netfs_unbuffered_read_iter(struct kiocb *iocb, struct iov_iter *iter);
ssize_t netfs_buffered_read_iter(struct kiocb *iocb, struct iov_iter *iter);
ssize_t netfs_file_read_iter(struct kiocb *iocb, struct iov_iter *iter);
/* High-level write API */
ssize_t netfs_perform_write(struct kiocb *iocb, struct iov_iter *iter,