// 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 ([email protected])
*/
#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"
static void netfs_prepare_dio_read_iterator(struct netfs_io_subrequest *subreq)
{
struct netfs_io_request *rreq = subreq->rreq;
size_t rsize;
rsize = umin(subreq->len, rreq->io_streams[0].sreq_max_len);
subreq->len = rsize;
if (unlikely(rreq->io_streams[0].sreq_max_segs)) {
size_t limit = netfs_limit_iter(&rreq->iter, 0, rsize,
rreq->io_streams[0].sreq_max_segs);
if (limit < rsize) {
subreq->len = limit;
trace_netfs_sreq(subreq, netfs_sreq_trace_limited);
}
}
trace_netfs_sreq(subreq, netfs_sreq_trace_prepare);
subreq->io_iter = rreq->iter;
iov_iter_truncate(&subreq->io_iter, subreq->len);
iov_iter_advance(&rreq->iter, subreq->len);
}
/*
* Perform a read to a buffer from the server, slicing up the region to be read
* according to the network rsize.
*/
static int netfs_dispatch_unbuffered_reads(struct netfs_io_request *rreq)
{
unsigned long long start = rreq->start;
ssize_t size = rreq->len;
int ret = 0;
atomic_set(&rreq->nr_outstanding, 1);
do {
struct netfs_io_subrequest *subreq;
ssize_t slice;
subreq = netfs_alloc_subrequest(rreq);
if (!subreq) {
ret = -ENOMEM;
break;
}
subreq->source = NETFS_DOWNLOAD_FROM_SERVER;
subreq->start = start;
subreq->len = size;
atomic_inc(&rreq->nr_outstanding);
spin_lock_bh(&rreq->lock);
list_add_tail(&subreq->rreq_link, &rreq->subrequests);
subreq->prev_donated = rreq->prev_donated;
rreq->prev_donated = 0;
trace_netfs_sreq(subreq, netfs_sreq_trace_added);
spin_unlock_bh(&rreq->lock);
netfs_stat(&netfs_n_rh_download);
if (rreq->netfs_ops->prepare_read) {
ret = rreq->netfs_ops->prepare_read(subreq);
if (ret < 0) {
atomic_dec(&rreq->nr_outstanding);
netfs_put_subrequest(subreq, false, netfs_sreq_trace_put_cancel);
break;
}
}
netfs_prepare_dio_read_iterator(subreq);
slice = subreq->len;
rreq->netfs_ops->issue_read(subreq);
size -= slice;
start += slice;
rreq->submitted += slice;
if (test_bit(NETFS_RREQ_BLOCKED, &rreq->flags) &&
test_bit(NETFS_RREQ_NONBLOCK, &rreq->flags))
break;
cond_resched();
} while (size > 0);
if (atomic_dec_and_test(&rreq->nr_outstanding))
netfs_rreq_terminated(rreq, false);
return ret;
}
/*
* Perform a read to an application buffer, bypassing the pagecache and the
* local disk cache.
*/
static int netfs_unbuffered_read(struct netfs_io_request *rreq, bool sync)
{
int ret;
_enter("R=%x %llx-%llx",
rreq->debug_id, rreq->start, rreq->start + rreq->len - 1);
if (rreq->len == 0) {
pr_err("Zero-sized read [R=%x]\n", rreq->debug_id);
return -EIO;
}
// TODO: Use bounce buffer if requested
inode_dio_begin(rreq->inode);
ret = netfs_dispatch_unbuffered_reads(rreq);
if (!rreq->submitted) {
netfs_put_request(rreq, false, netfs_rreq_trace_put_no_submit);
inode_dio_end(rreq->inode);
ret = 0;
goto out;
}
if (sync) {
trace_netfs_rreq(rreq, netfs_rreq_trace_wait_ip);
wait_on_bit(&rreq->flags, NETFS_RREQ_IN_PROGRESS,
TASK_UNINTERRUPTIBLE);
ret = rreq->error;
if (ret == 0 && rreq->submitted < rreq->len &&
rreq->origin != NETFS_DIO_READ) {
trace_netfs_failure(rreq, NULL, ret, netfs_fail_short_read);
ret = -EIO;
}
} else {
ret = -EIOCBQUEUED;
}
out:
_leave(" = %d", ret);
return ret;
}
/**
* 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.
*/
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 sync = 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 (!sync)
rreq->iocb = iocb;
ret = netfs_unbuffered_read(rreq, sync);
if (ret < 0)
goto out; /* May be -EIOCBQUEUED */
if (sync) {
// 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;
return ret;
}
EXPORT_SYMBOL(netfs_unbuffered_read_iter_locked);
/**
* 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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