--- /dev/null
+// 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 (dhowells@redhat.com)
+ */
+
+#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 <linux/netfs.h>
+#include "internal.h"
+
+MODULE_DESCRIPTION("Network fs support");
+MODULE_AUTHOR("Red Hat, Inc.");
+MODULE_LICENSE("GPL");
+
+unsigned netfs_debug;
+module_param_named(debug, netfs_debug, uint, S_IWUSR | S_IRUGO);
+MODULE_PARM_DESC(netfs_debug, "Netfs support debugging mask");
+
+static void netfs_rreq_work(struct work_struct *);
+static void __netfs_put_subrequest(struct netfs_read_subrequest *, bool);
+
+static void netfs_put_subrequest(struct netfs_read_subrequest *subreq,
+ bool was_async)
+{
+ if (refcount_dec_and_test(&subreq->usage))
+ __netfs_put_subrequest(subreq, was_async);
+}
+
+static struct netfs_read_request *netfs_alloc_read_request(
+ const struct netfs_read_request_ops *ops, void *netfs_priv,
+ struct file *file)
+{
+ static atomic_t debug_ids;
+ struct netfs_read_request *rreq;
+
+ rreq = kzalloc(sizeof(struct netfs_read_request), GFP_KERNEL);
+ if (rreq) {
+ rreq->netfs_ops = ops;
+ rreq->netfs_priv = netfs_priv;
+ rreq->inode = file_inode(file);
+ rreq->i_size = i_size_read(rreq->inode);
+ rreq->debug_id = atomic_inc_return(&debug_ids);
+ INIT_LIST_HEAD(&rreq->subrequests);
+ INIT_WORK(&rreq->work, netfs_rreq_work);
+ refcount_set(&rreq->usage, 1);
+ __set_bit(NETFS_RREQ_IN_PROGRESS, &rreq->flags);
+ ops->init_rreq(rreq, file);
+ }
+
+ return rreq;
+}
+
+static void netfs_get_read_request(struct netfs_read_request *rreq)
+{
+ refcount_inc(&rreq->usage);
+}
+
+static void netfs_rreq_clear_subreqs(struct netfs_read_request *rreq,
+ bool was_async)
+{
+ struct netfs_read_subrequest *subreq;
+
+ while (!list_empty(&rreq->subrequests)) {
+ subreq = list_first_entry(&rreq->subrequests,
+ struct netfs_read_subrequest, rreq_link);
+ list_del(&subreq->rreq_link);
+ netfs_put_subrequest(subreq, was_async);
+ }
+}
+
+static void netfs_free_read_request(struct work_struct *work)
+{
+ struct netfs_read_request *rreq =
+ container_of(work, struct netfs_read_request, work);
+ netfs_rreq_clear_subreqs(rreq, false);
+ if (rreq->netfs_priv)
+ rreq->netfs_ops->cleanup(rreq->mapping, rreq->netfs_priv);
+ kfree(rreq);
+}
+
+static void netfs_put_read_request(struct netfs_read_request *rreq, bool was_async)
+{
+ if (refcount_dec_and_test(&rreq->usage)) {
+ if (was_async) {
+ rreq->work.func = netfs_free_read_request;
+ if (!queue_work(system_unbound_wq, &rreq->work))
+ BUG();
+ } else {
+ netfs_free_read_request(&rreq->work);
+ }
+ }
+}
+
+/*
+ * Allocate and partially initialise an I/O request structure.
+ */
+static struct netfs_read_subrequest *netfs_alloc_subrequest(
+ struct netfs_read_request *rreq)
+{
+ struct netfs_read_subrequest *subreq;
+
+ subreq = kzalloc(sizeof(struct netfs_read_subrequest), GFP_KERNEL);
+ if (subreq) {
+ INIT_LIST_HEAD(&subreq->rreq_link);
+ refcount_set(&subreq->usage, 2);
+ subreq->rreq = rreq;
+ netfs_get_read_request(rreq);
+ }
+
+ return subreq;
+}
+
+static void netfs_get_read_subrequest(struct netfs_read_subrequest *subreq)
+{
+ refcount_inc(&subreq->usage);
+}
+
+static void __netfs_put_subrequest(struct netfs_read_subrequest *subreq,
+ bool was_async)
+{
+ struct netfs_read_request *rreq = subreq->rreq;
+
+ kfree(subreq);
+ netfs_put_read_request(rreq, was_async);
+}
+
+/*
+ * Clear the unread part of an I/O request.
+ */
+static void netfs_clear_unread(struct netfs_read_subrequest *subreq)
+{
+ struct iov_iter iter;
+
+ iov_iter_xarray(&iter, WRITE, &subreq->rreq->mapping->i_pages,
+ subreq->start + subreq->transferred,
+ subreq->len - subreq->transferred);
+ iov_iter_zero(iov_iter_count(&iter), &iter);
+}
+
+/*
+ * Fill a subrequest region with zeroes.
+ */
+static void netfs_fill_with_zeroes(struct netfs_read_request *rreq,
+ struct netfs_read_subrequest *subreq)
+{
+ __set_bit(NETFS_SREQ_CLEAR_TAIL, &subreq->flags);
+ netfs_subreq_terminated(subreq, 0, false);
+}
+
+/*
+ * 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_read_request *rreq,
+ struct netfs_read_subrequest *subreq)
+{
+ rreq->netfs_ops->issue_op(subreq);
+}
+
+/*
+ * Release those waiting.
+ */
+static void netfs_rreq_completed(struct netfs_read_request *rreq, bool was_async)
+{
+ netfs_rreq_clear_subreqs(rreq, was_async);
+ netfs_put_read_request(rreq, was_async);
+}
+
+/*
+ * Unlock the pages in a read operation. We need to set PG_fscache on any
+ * pages we're going to write back before we unlock them.
+ */
+static void netfs_rreq_unlock(struct netfs_read_request *rreq)
+{
+ struct netfs_read_subrequest *subreq;
+ struct page *page;
+ unsigned int iopos, account = 0;
+ pgoff_t start_page = rreq->start / PAGE_SIZE;
+ pgoff_t last_page = ((rreq->start + rreq->len) / PAGE_SIZE) - 1;
+ bool subreq_failed = false;
+ int i;
+
+ XA_STATE(xas, &rreq->mapping->i_pages, start_page);
+
+ if (test_bit(NETFS_RREQ_FAILED, &rreq->flags)) {
+ __clear_bit(NETFS_RREQ_WRITE_TO_CACHE, &rreq->flags);
+ list_for_each_entry(subreq, &rreq->subrequests, rreq_link) {
+ __clear_bit(NETFS_SREQ_WRITE_TO_CACHE, &subreq->flags);
+ }
+ }
+
+ /* Walk through the pagecache and the I/O request lists simultaneously.
+ * We may have a mixture of cached and uncached sections and we only
+ * really want to write out the uncached sections. This is slightly
+ * complicated by the possibility that we might have huge pages with a
+ * mixture inside.
+ */
+ subreq = list_first_entry(&rreq->subrequests,
+ struct netfs_read_subrequest, rreq_link);
+ iopos = 0;
+ subreq_failed = (subreq->error < 0);
+
+ rcu_read_lock();
+ xas_for_each(&xas, page, last_page) {
+ unsigned int pgpos = (page->index - start_page) * PAGE_SIZE;
+ unsigned int pgend = pgpos + thp_size(page);
+ bool pg_failed = false;
+
+ for (;;) {
+ if (!subreq) {
+ pg_failed = true;
+ break;
+ }
+ if (test_bit(NETFS_SREQ_WRITE_TO_CACHE, &subreq->flags))
+ set_page_fscache(page);
+ pg_failed |= subreq_failed;
+ if (pgend < iopos + subreq->len)
+ break;
+
+ account += subreq->transferred;
+ iopos += subreq->len;
+ if (!list_is_last(&subreq->rreq_link, &rreq->subrequests)) {
+ subreq = list_next_entry(subreq, rreq_link);
+ subreq_failed = (subreq->error < 0);
+ } else {
+ subreq = NULL;
+ subreq_failed = false;
+ }
+ if (pgend == iopos)
+ break;
+ }
+
+ if (!pg_failed) {
+ for (i = 0; i < thp_nr_pages(page); i++)
+ flush_dcache_page(page);
+ SetPageUptodate(page);
+ }
+
+ if (!test_bit(NETFS_RREQ_DONT_UNLOCK_PAGES, &rreq->flags)) {
+ if (page->index == rreq->no_unlock_page &&
+ test_bit(NETFS_RREQ_NO_UNLOCK_PAGE, &rreq->flags))
+ _debug("no unlock");
+ else
+ unlock_page(page);
+ }
+ }
+ rcu_read_unlock();
+
+ task_io_account_read(account);
+ if (rreq->netfs_ops->done)
+ rreq->netfs_ops->done(rreq);
+}
+
+/*
+ * Handle a short read.
+ */
+static void netfs_rreq_short_read(struct netfs_read_request *rreq,
+ struct netfs_read_subrequest *subreq)
+{
+ __clear_bit(NETFS_SREQ_SHORT_READ, &subreq->flags);
+ __set_bit(NETFS_SREQ_SEEK_DATA_READ, &subreq->flags);
+
+ netfs_get_read_subrequest(subreq);
+ atomic_inc(&rreq->nr_rd_ops);
+ netfs_read_from_server(rreq, subreq);
+}
+
+/*
+ * Resubmit any short or failed operations. Returns true if we got the rreq
+ * ref back.
+ */
+static bool netfs_rreq_perform_resubmissions(struct netfs_read_request *rreq)
+{
+ struct netfs_read_subrequest *subreq;
+
+ WARN_ON(in_interrupt());
+
+ /* We don't want terminating submissions trying to wake us up whilst
+ * we're still going through the list.
+ */
+ atomic_inc(&rreq->nr_rd_ops);
+
+ __clear_bit(NETFS_RREQ_INCOMPLETE_IO, &rreq->flags);
+ list_for_each_entry(subreq, &rreq->subrequests, rreq_link) {
+ if (subreq->error) {
+ if (subreq->source != NETFS_READ_FROM_CACHE)
+ break;
+ subreq->source = NETFS_DOWNLOAD_FROM_SERVER;
+ subreq->error = 0;
+ netfs_get_read_subrequest(subreq);
+ atomic_inc(&rreq->nr_rd_ops);
+ netfs_read_from_server(rreq, subreq);
+ } else if (test_bit(NETFS_SREQ_SHORT_READ, &subreq->flags)) {
+ netfs_rreq_short_read(rreq, subreq);
+ }
+ }
+
+ /* If we decrement nr_rd_ops to 0, the usage ref belongs to us. */
+ if (atomic_dec_and_test(&rreq->nr_rd_ops))
+ return true;
+
+ wake_up_var(&rreq->nr_rd_ops);
+ return false;
+}
+
+/*
+ * 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_read_request *rreq, bool was_async)
+{
+again:
+ if (!test_bit(NETFS_RREQ_FAILED, &rreq->flags) &&
+ test_bit(NETFS_RREQ_INCOMPLETE_IO, &rreq->flags)) {
+ if (netfs_rreq_perform_resubmissions(rreq))
+ goto again;
+ return;
+ }
+
+ netfs_rreq_unlock(rreq);
+
+ clear_bit_unlock(NETFS_RREQ_IN_PROGRESS, &rreq->flags);
+ wake_up_bit(&rreq->flags, NETFS_RREQ_IN_PROGRESS);
+
+ netfs_rreq_completed(rreq, was_async);
+}
+
+static void netfs_rreq_work(struct work_struct *work)
+{
+ struct netfs_read_request *rreq =
+ container_of(work, struct netfs_read_request, work);
+ netfs_rreq_assess(rreq, false);
+}
+
+/*
+ * 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_read_request *rreq,
+ bool was_async)
+{
+ if (test_bit(NETFS_RREQ_INCOMPLETE_IO, &rreq->flags) &&
+ was_async) {
+ if (!queue_work(system_unbound_wq, &rreq->work))
+ BUG();
+ } else {
+ netfs_rreq_assess(rreq, 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_read_subrequest *subreq,
+ ssize_t transferred_or_error,
+ bool was_async)
+{
+ struct netfs_read_request *rreq = subreq->rreq;
+ int u;
+
+ _enter("[%u]{%llx,%lx},%zd",
+ subreq->debug_index, subreq->start, subreq->flags,
+ transferred_or_error);
+
+ if (IS_ERR_VALUE(transferred_or_error)) {
+ subreq->error = transferred_or_error;
+ goto failed;
+ }
+
+ if (WARN(transferred_or_error > subreq->len - subreq->transferred,
+ "Subreq overread: R%x[%x] %zd > %zu - %zu",
+ rreq->debug_id, subreq->debug_index,
+ transferred_or_error, subreq->len, subreq->transferred))
+ transferred_or_error = subreq->len - subreq->transferred;
+
+ subreq->error = 0;
+ subreq->transferred += transferred_or_error;
+ if (subreq->transferred < subreq->len)
+ goto incomplete;
+
+complete:
+ __clear_bit(NETFS_SREQ_NO_PROGRESS, &subreq->flags);
+ if (test_bit(NETFS_SREQ_WRITE_TO_CACHE, &subreq->flags))
+ set_bit(NETFS_RREQ_WRITE_TO_CACHE, &rreq->flags);
+
+out:
+ /* If we decrement nr_rd_ops to 0, the ref belongs to us. */
+ u = atomic_dec_return(&rreq->nr_rd_ops);
+ if (u == 0)
+ netfs_rreq_terminated(rreq, was_async);
+ else if (u == 1)
+ wake_up_var(&rreq->nr_rd_ops);
+
+ netfs_put_subrequest(subreq, was_async);
+ return;
+
+incomplete:
+ if (test_bit(NETFS_SREQ_CLEAR_TAIL, &subreq->flags)) {
+ netfs_clear_unread(subreq);
+ subreq->transferred = subreq->len;
+ goto complete;
+ }
+
+ if (transferred_or_error == 0) {
+ if (__test_and_set_bit(NETFS_SREQ_NO_PROGRESS, &subreq->flags)) {
+ subreq->error = -ENODATA;
+ goto failed;
+ }
+ } else {
+ __clear_bit(NETFS_SREQ_NO_PROGRESS, &subreq->flags);
+ }
+
+ __set_bit(NETFS_SREQ_SHORT_READ, &subreq->flags);
+ set_bit(NETFS_RREQ_INCOMPLETE_IO, &rreq->flags);
+ goto out;
+
+failed:
+ if (subreq->source == NETFS_READ_FROM_CACHE) {
+ set_bit(NETFS_RREQ_INCOMPLETE_IO, &rreq->flags);
+ } else {
+ set_bit(NETFS_RREQ_FAILED, &rreq->flags);
+ rreq->error = subreq->error;
+ }
+ goto out;
+}
+EXPORT_SYMBOL(netfs_subreq_terminated);
+
+static enum netfs_read_source netfs_cache_prepare_read(struct netfs_read_subrequest *subreq,
+ loff_t i_size)
+{
+ struct netfs_read_request *rreq = subreq->rreq;
+
+ if (subreq->start >= rreq->i_size)
+ return NETFS_FILL_WITH_ZEROES;
+ return NETFS_DOWNLOAD_FROM_SERVER;
+}
+
+/*
+ * Work out what sort of subrequest the next one will be.
+ */
+static enum netfs_read_source
+netfs_rreq_prepare_read(struct netfs_read_request *rreq,
+ struct netfs_read_subrequest *subreq)
+{
+ enum netfs_read_source source;
+
+ _enter("%llx-%llx,%llx", subreq->start, subreq->start + subreq->len, rreq->i_size);
+
+ source = netfs_cache_prepare_read(subreq, rreq->i_size);
+ if (source == NETFS_INVALID_READ)
+ goto out;
+
+ if (source == NETFS_DOWNLOAD_FROM_SERVER) {
+ /* Call out to the netfs to let it shrink the request to fit
+ * its own I/O sizes and boundaries. If it shinks it here, it
+ * will be called again to make simultaneous calls; if it wants
+ * to make serial calls, it can indicate a short read and then
+ * we will call it again.
+ */
+ if (subreq->len > rreq->i_size - subreq->start)
+ subreq->len = rreq->i_size - subreq->start;
+
+ if (rreq->netfs_ops->clamp_length &&
+ !rreq->netfs_ops->clamp_length(subreq)) {
+ source = NETFS_INVALID_READ;
+ goto out;
+ }
+ }
+
+ if (WARN_ON(subreq->len == 0))
+ source = NETFS_INVALID_READ;
+
+out:
+ subreq->source = source;
+ return source;
+}
+
+/*
+ * Slice off a piece of a read request and submit an I/O request for it.
+ */
+static bool netfs_rreq_submit_slice(struct netfs_read_request *rreq,
+ unsigned int *_debug_index)
+{
+ struct netfs_read_subrequest *subreq;
+ enum netfs_read_source source;
+
+ subreq = netfs_alloc_subrequest(rreq);
+ if (!subreq)
+ return false;
+
+ subreq->debug_index = (*_debug_index)++;
+ subreq->start = rreq->start + rreq->submitted;
+ subreq->len = rreq->len - rreq->submitted;
+
+ _debug("slice %llx,%zx,%zx", subreq->start, subreq->len, rreq->submitted);
+ list_add_tail(&subreq->rreq_link, &rreq->subrequests);
+
+ /* Call out to the cache to find out what it can do with the remaining
+ * subset. It tells us in subreq->flags what it decided should be done
+ * and adjusts subreq->len down if the subset crosses a cache boundary.
+ *
+ * Then when we hand the subset, it can choose to take a subset of that
+ * (the starts must coincide), in which case, we go around the loop
+ * again and ask it to download the next piece.
+ */
+ source = netfs_rreq_prepare_read(rreq, subreq);
+ if (source == NETFS_INVALID_READ)
+ goto subreq_failed;
+
+ atomic_inc(&rreq->nr_rd_ops);
+
+ rreq->submitted += subreq->len;
+
+ switch (source) {
+ case NETFS_FILL_WITH_ZEROES:
+ netfs_fill_with_zeroes(rreq, subreq);
+ break;
+ case NETFS_DOWNLOAD_FROM_SERVER:
+ netfs_read_from_server(rreq, subreq);
+ break;
+ default:
+ BUG();
+ }
+
+ return true;
+
+subreq_failed:
+ rreq->error = subreq->error;
+ netfs_put_subrequest(subreq, false);
+ return false;
+}
+
+static void netfs_rreq_expand(struct netfs_read_request *rreq,
+ struct readahead_control *ractl)
+{
+ /* Give the netfs a chance to change the request parameters. The
+ * resultant request must contain the original region.
+ */
+ if (rreq->netfs_ops->expand_readahead)
+ rreq->netfs_ops->expand_readahead(rreq);
+
+ /* Expand the request if the cache wants it to start earlier. Note
+ * that the expansion may get further extended if the VM wishes to
+ * insert THPs and the preferred start and/or end wind up in the middle
+ * of THPs.
+ *
+ * If this is the case, however, the THP size should be an integer
+ * multiple of the cache granule size, so we get a whole number of
+ * granules to deal with.
+ */
+ if (rreq->start != readahead_pos(ractl) ||
+ rreq->len != readahead_length(ractl)) {
+ readahead_expand(ractl, rreq->start, rreq->len);
+ rreq->start = readahead_pos(ractl);
+ rreq->len = readahead_length(ractl);
+ }
+}
+
+/**
+ * netfs_readahead - Helper to manage a read request
+ * @ractl: The description of the readahead request
+ * @ops: The network filesystem's operations for the helper to use
+ * @netfs_priv: Private netfs data to be retained in the request
+ *
+ * Fulfil a readahead request by drawing data from the cache if possible, or
+ * the netfs if not. Space beyond the EOF is zero-filled. Multiple I/O
+ * requests from different sources will get munged together. If necessary, the
+ * readahead window can be expanded in either direction to a more convenient
+ * alighment for RPC efficiency or to make storage in the cache feasible.
+ *
+ * The calling netfs must provide a table of operations, only one of which,
+ * issue_op, is mandatory. It may also be passed a private token, which will
+ * be retained in rreq->netfs_priv and will be cleaned up by ops->cleanup().
+ *
+ * This is usable whether or not caching is enabled.
+ */
+void netfs_readahead(struct readahead_control *ractl,
+ const struct netfs_read_request_ops *ops,
+ void *netfs_priv)
+{
+ struct netfs_read_request *rreq;
+ struct page *page;
+ unsigned int debug_index = 0;
+
+ _enter("%lx,%x", readahead_index(ractl), readahead_count(ractl));
+
+ if (readahead_count(ractl) == 0)
+ goto cleanup;
+
+ rreq = netfs_alloc_read_request(ops, netfs_priv, ractl->file);
+ if (!rreq)
+ goto cleanup;
+ rreq->mapping = ractl->mapping;
+ rreq->start = readahead_pos(ractl);
+ rreq->len = readahead_length(ractl);
+
+ netfs_rreq_expand(rreq, ractl);
+
+ atomic_set(&rreq->nr_rd_ops, 1);
+ do {
+ if (!netfs_rreq_submit_slice(rreq, &debug_index))
+ break;
+
+ } while (rreq->submitted < rreq->len);
+
+ /* Drop the refs on the pages here rather than in the cache or
+ * filesystem. The locks will be dropped in netfs_rreq_unlock().
+ */
+ while ((page = readahead_page(ractl)))
+ put_page(page);
+
+ /* If we decrement nr_rd_ops to 0, the ref belongs to us. */
+ if (atomic_dec_and_test(&rreq->nr_rd_ops))
+ netfs_rreq_assess(rreq, false);
+ return;
+
+cleanup:
+ if (netfs_priv)
+ ops->cleanup(ractl->mapping, netfs_priv);
+ return;
+}
+EXPORT_SYMBOL(netfs_readahead);
+
+/**
+ * netfs_page - Helper to manage a readpage request
+ * @file: The file to read from
+ * @page: The page to read
+ * @ops: The network filesystem's operations for the helper to use
+ * @netfs_priv: Private netfs data to be retained in the request
+ *
+ * Fulfil a readpage request by drawing data from the cache if possible, or the
+ * netfs if not. Space beyond the EOF is zero-filled. Multiple I/O requests
+ * from different sources will get munged together.
+ *
+ * The calling netfs must provide a table of operations, only one of which,
+ * issue_op, is mandatory. It may also be passed a private token, which will
+ * be retained in rreq->netfs_priv and will be cleaned up by ops->cleanup().
+ *
+ * This is usable whether or not caching is enabled.
+ */
+int netfs_readpage(struct file *file,
+ struct page *page,
+ const struct netfs_read_request_ops *ops,
+ void *netfs_priv)
+{
+ struct netfs_read_request *rreq;
+ unsigned int debug_index = 0;
+ int ret;
+
+ _enter("%lx", page_index(page));
+
+ rreq = netfs_alloc_read_request(ops, netfs_priv, file);
+ if (!rreq) {
+ if (netfs_priv)
+ ops->cleanup(netfs_priv, page_file_mapping(page));
+ unlock_page(page);
+ return -ENOMEM;
+ }
+ rreq->mapping = page_file_mapping(page);
+ rreq->start = page_index(page) * PAGE_SIZE;
+ rreq->len = thp_size(page);
+
+ netfs_get_read_request(rreq);
+
+ atomic_set(&rreq->nr_rd_ops, 1);
+ do {
+ if (!netfs_rreq_submit_slice(rreq, &debug_index))
+ break;
+
+ } while (rreq->submitted < rreq->len);
+
+ /* Keep nr_rd_ops incremented so that the ref always belongs to us, and
+ * the service code isn't punted off to a random thread pool to
+ * process.
+ */
+ do {
+ wait_var_event(&rreq->nr_rd_ops, atomic_read(&rreq->nr_rd_ops) == 1);
+ netfs_rreq_assess(rreq, false);
+ } while (test_bit(NETFS_RREQ_IN_PROGRESS, &rreq->flags));
+
+ ret = rreq->error;
+ if (ret == 0 && rreq->submitted < rreq->len)
+ ret = -EIO;
+ netfs_put_read_request(rreq, false);
+ return ret;
+}
+EXPORT_SYMBOL(netfs_readpage);
projects / users / jedix / linux-maple.git / commitdiff