linux/fs/netfs/io.c

// SPDX-License-Identifier: GPL-2.0-or-later
/* Network filesystem high-level read support.
 *
 * Copyright (C) 2021 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells ([email protected])
 */

#include <linux/module.h>
#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 "internal.h"

/*
 * Clear the unread part of an I/O request.
 */
static void netfs_clear_unread(struct netfs_io_subrequest *subreq)
{ … }

static void netfs_cache_read_terminated(void *priv, ssize_t transferred_or_error,
					bool was_async)
{ … }

/*
 * Issue a read against the cache.
 * - Eats the caller's ref on subreq.
 */
static void netfs_read_from_cache(struct netfs_io_request *rreq,
				  struct netfs_io_subrequest *subreq,
				  enum netfs_read_from_hole read_hole)
{ … }

/*
 * Fill a subrequest region with zeroes.
 */
static void netfs_fill_with_zeroes(struct netfs_io_request *rreq,
				   struct netfs_io_subrequest *subreq)
{ … }

/*
 * Ask the netfs to issue a read request to the server for us.
 *
 * The netfs is expected to read from subreq->pos + subreq->transferred to
 * subreq->pos + subreq->len - 1.  It may not backtrack and write data into the
 * buffer prior to the transferred point as it might clobber dirty data
 * obtained from the cache.
 *
 * Alternatively, the netfs is allowed to indicate one of two things:
 *
 * - NETFS_SREQ_SHORT_READ: A short read - it will get called again to try and
 *   make progress.
 *
 * - NETFS_SREQ_CLEAR_TAIL: A short read - the rest of the buffer will be
 *   cleared.
 */
static void netfs_read_from_server(struct netfs_io_request *rreq,
				   struct netfs_io_subrequest *subreq)
{ … }

/*
 * Release those waiting.
 */
static void netfs_rreq_completed(struct netfs_io_request *rreq, bool was_async)
{ … }

/*
 * Handle a short read.
 */
static void netfs_rreq_short_read(struct netfs_io_request *rreq,
				  struct netfs_io_subrequest *subreq)
{ … }

/*
 * Reset the subrequest iterator prior to resubmission.
 */
static void netfs_reset_subreq_iter(struct netfs_io_request *rreq,
				    struct netfs_io_subrequest *subreq)
{ … }

/*
 * Resubmit any short or failed operations.  Returns true if we got the rreq
 * ref back.
 */
static bool netfs_rreq_perform_resubmissions(struct netfs_io_request *rreq)
{ … }

/*
 * Check to see if the data read is still valid.
 */
static void netfs_rreq_is_still_valid(struct netfs_io_request *rreq)
{ … }

/*
 * Determine how much we can admit to having read from a DIO read.
 */
static void netfs_rreq_assess_dio(struct netfs_io_request *rreq)
{ … }

/*
 * Assess the state of a read request and decide what to do next.
 *
 * Note that we could be in an ordinary kernel thread, on a workqueue or in
 * softirq context at this point.  We inherit a ref from the caller.
 */
static void netfs_rreq_assess(struct netfs_io_request *rreq, bool was_async)
{ … }

static void netfs_rreq_work(struct work_struct *work)
{ … }

/*
 * Handle the completion of all outstanding I/O operations on a read request.
 * We inherit a ref from the caller.
 */
static void netfs_rreq_terminated(struct netfs_io_request *rreq,
				  bool was_async)
{ … }

/**
 * netfs_subreq_terminated - Note the termination of an I/O operation.
 * @subreq: The I/O request that has terminated.
 * @transferred_or_error: The amount of data transferred or an error code.
 * @was_async: The termination was asynchronous
 *
 * This tells the read helper that a contributory I/O operation has terminated,
 * one way or another, and that it should integrate the results.
 *
 * The caller indicates in @transferred_or_error the outcome of the operation,
 * supplying a positive value to indicate the number of bytes transferred, 0 to
 * indicate a failure to transfer anything that should be retried or a negative
 * error code.  The helper will look after reissuing I/O operations as
 * appropriate and writing downloaded data to the cache.
 *
 * If @was_async is true, the caller might be running in softirq or interrupt
 * context and we can't sleep.
 */
void netfs_subreq_terminated(struct netfs_io_subrequest *subreq,
			     ssize_t transferred_or_error,
			     bool was_async)
{ … }
EXPORT_SYMBOL(…);

static enum netfs_io_source netfs_cache_prepare_read(struct netfs_io_subrequest *subreq,
						       loff_t i_size)
{ … }

/*
 * Work out what sort of subrequest the next one will be.
 */
static enum netfs_io_source
netfs_rreq_prepare_read(struct netfs_io_request *rreq,
			struct netfs_io_subrequest *subreq,
			struct iov_iter *io_iter)
{ … }

/*
 * Slice off a piece of a read request and submit an I/O request for it.
 */
static bool netfs_rreq_submit_slice(struct netfs_io_request *rreq,
				    struct iov_iter *io_iter)
{ … }

/*
 * Begin the process of reading in a chunk of data, where that data may be
 * stitched together from multiple sources, including multiple servers and the
 * local cache.
 */
int netfs_begin_read(struct netfs_io_request *rreq, bool sync)
{ … }