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// SPDX-License-Identifier: GPL-2.0-or-later
/* Direct I/O support.
*
* Copyright (C) 2023 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.com)
*/
#include <linux/export.h>
#include <linux/fs.h>
#include <linux/mm.h>
#include <linux/pagemap.h>
#include <linux/slab.h>
#include <linux/uio.h>
#include <linux/sched/mm.h>
#include <linux/task_io_accounting_ops.h>
#include <linux/netfs.h>
#include "internal.h"
/**
* netfs_unbuffered_read_iter_locked - Perform an unbuffered or direct I/O read
* @iocb: The I/O control descriptor describing the read
* @iter: The output buffer (also specifies read length)
*
* Perform an unbuffered I/O or direct I/O from the file in @iocb to the
* output buffer. No use is made of the pagecache.
*
* The caller must hold any appropriate locks.
*/
static ssize_t netfs_unbuffered_read_iter_locked(struct kiocb *iocb, struct iov_iter *iter)
{
struct netfs_io_request *rreq;
ssize_t ret;
size_t orig_count = iov_iter_count(iter);
bool async = !is_sync_kiocb(iocb);
_enter("");
if (!orig_count)
return 0; /* Don't update atime */
ret = kiocb_write_and_wait(iocb, orig_count);
if (ret < 0)
return ret;
file_accessed(iocb->ki_filp);
rreq = netfs_alloc_request(iocb->ki_filp->f_mapping, iocb->ki_filp,
iocb->ki_pos, orig_count,
NETFS_DIO_READ);
if (IS_ERR(rreq))
return PTR_ERR(rreq);
netfs_stat(&netfs_n_rh_dio_read);
trace_netfs_read(rreq, rreq->start, rreq->len, netfs_read_trace_dio_read);
/* If this is an async op, we have to keep track of the destination
* buffer for ourselves as the caller's iterator will be trashed when
* we return.
*
* In such a case, extract an iterator to represent as much of the the
* output buffer as we can manage. Note that the extraction might not
* be able to allocate a sufficiently large bvec array and may shorten
* the request.
*/
if (user_backed_iter(iter)) {
ret = netfs_extract_user_iter(iter, rreq->len, &rreq->iter, 0);
if (ret < 0)
goto out;
rreq->direct_bv = (struct bio_vec *)rreq->iter.bvec;
rreq->direct_bv_count = ret;
rreq->direct_bv_unpin = iov_iter_extract_will_pin(iter);
rreq->len = iov_iter_count(&rreq->iter);
} else {
rreq->iter = *iter;
rreq->len = orig_count;
rreq->direct_bv_unpin = false;
iov_iter_advance(iter, orig_count);
}
// TODO: Set up bounce buffer if needed
if (async)
rreq->iocb = iocb;
ret = netfs_begin_read(rreq, is_sync_kiocb(iocb));
if (ret < 0)
goto out; /* May be -EIOCBQUEUED */
if (!async) {
// TODO: Copy from bounce buffer
iocb->ki_pos += rreq->transferred;
ret = rreq->transferred;
}
out:
netfs_put_request(rreq, false, netfs_rreq_trace_put_return);
if (ret > 0)
orig_count -= ret;
if (ret != -EIOCBQUEUED)
iov_iter_revert(iter, orig_count - iov_iter_count(iter));
return ret;
}
/**
* netfs_unbuffered_read_iter - Perform an unbuffered or direct I/O read
* @iocb: The I/O control descriptor describing the read
* @iter: The output buffer (also specifies read length)
*
* Perform an unbuffered I/O or direct I/O from the file in @iocb to the
* output buffer. No use is made of the pagecache.
*/
ssize_t netfs_unbuffered_read_iter(struct kiocb *iocb, struct iov_iter *iter)
{
struct inode *inode = file_inode(iocb->ki_filp);
ssize_t ret;
if (!iter->count)
return 0; /* Don't update atime */
ret = netfs_start_io_direct(inode);
if (ret == 0) {
ret = netfs_unbuffered_read_iter_locked(iocb, iter);
netfs_end_io_direct(inode);
}
return ret;
}
EXPORT_SYMBOL(netfs_unbuffered_read_iter);
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