796a404964
netfslib currently defers dropping the ref on the folios it obtains during
readahead to after it has started I/O on the basis that we can do it whilst
we wait for the I/O to complete, but this runs the risk of the I/O
collection racing with this in future.
Furthermore, Matthew Wilcox strongly suggests that the refs should be
dropped immediately, as readahead_folio() does (netfslib is using
__readahead_batch() which doesn't drop the refs).
Fixes: ee4cdf7ba8
("netfs: Speed up buffered reading")
Suggested-by: Matthew Wilcox <willy@infradead.org>
Signed-off-by: David Howells <dhowells@redhat.com>
Link: https://lore.kernel.org/r/3771538.1728052438@warthog.procyon.org.uk
cc: Jeff Layton <jlayton@kernel.org>
cc: netfs@lists.linux.dev
cc: linux-fsdevel@vger.kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>
898 lines
26 KiB
C
898 lines
26 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
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/* Network filesystem high-level buffered read support.
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*
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* Copyright (C) 2021 Red Hat, Inc. All Rights Reserved.
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* Written by David Howells (dhowells@redhat.com)
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*/
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#include <linux/export.h>
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#include <linux/task_io_accounting_ops.h>
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#include "internal.h"
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static void netfs_cache_expand_readahead(struct netfs_io_request *rreq,
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unsigned long long *_start,
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unsigned long long *_len,
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unsigned long long i_size)
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{
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struct netfs_cache_resources *cres = &rreq->cache_resources;
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if (cres->ops && cres->ops->expand_readahead)
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cres->ops->expand_readahead(cres, _start, _len, i_size);
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}
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static void netfs_rreq_expand(struct netfs_io_request *rreq,
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struct readahead_control *ractl)
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{
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/* Give the cache a chance to change the request parameters. The
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* resultant request must contain the original region.
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*/
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netfs_cache_expand_readahead(rreq, &rreq->start, &rreq->len, rreq->i_size);
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/* Give the netfs a chance to change the request parameters. The
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* resultant request must contain the original region.
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*/
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if (rreq->netfs_ops->expand_readahead)
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rreq->netfs_ops->expand_readahead(rreq);
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/* Expand the request if the cache wants it to start earlier. Note
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* that the expansion may get further extended if the VM wishes to
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* insert THPs and the preferred start and/or end wind up in the middle
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* of THPs.
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*
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* If this is the case, however, the THP size should be an integer
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* multiple of the cache granule size, so we get a whole number of
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* granules to deal with.
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*/
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if (rreq->start != readahead_pos(ractl) ||
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rreq->len != readahead_length(ractl)) {
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readahead_expand(ractl, rreq->start, rreq->len);
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rreq->start = readahead_pos(ractl);
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rreq->len = readahead_length(ractl);
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trace_netfs_read(rreq, readahead_pos(ractl), readahead_length(ractl),
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netfs_read_trace_expanded);
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}
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}
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/*
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* Begin an operation, and fetch the stored zero point value from the cookie if
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* available.
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*/
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static int netfs_begin_cache_read(struct netfs_io_request *rreq, struct netfs_inode *ctx)
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{
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return fscache_begin_read_operation(&rreq->cache_resources, netfs_i_cookie(ctx));
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}
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/*
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* Decant the list of folios to read into a rolling buffer.
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*/
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static size_t netfs_load_buffer_from_ra(struct netfs_io_request *rreq,
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struct folio_queue *folioq,
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struct folio_batch *put_batch)
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{
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unsigned int order, nr;
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size_t size = 0;
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nr = __readahead_batch(rreq->ractl, (struct page **)folioq->vec.folios,
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ARRAY_SIZE(folioq->vec.folios));
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folioq->vec.nr = nr;
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for (int i = 0; i < nr; i++) {
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struct folio *folio = folioq_folio(folioq, i);
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trace_netfs_folio(folio, netfs_folio_trace_read);
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order = folio_order(folio);
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folioq->orders[i] = order;
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size += PAGE_SIZE << order;
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if (!folio_batch_add(put_batch, folio))
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folio_batch_release(put_batch);
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}
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for (int i = nr; i < folioq_nr_slots(folioq); i++)
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folioq_clear(folioq, i);
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return size;
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}
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/*
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* netfs_prepare_read_iterator - Prepare the subreq iterator for I/O
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* @subreq: The subrequest to be set up
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*
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* Prepare the I/O iterator representing the read buffer on a subrequest for
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* the filesystem to use for I/O (it can be passed directly to a socket). This
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* is intended to be called from the ->issue_read() method once the filesystem
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* has trimmed the request to the size it wants.
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*
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* Returns the limited size if successful and -ENOMEM if insufficient memory
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* available.
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*
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* [!] NOTE: This must be run in the same thread as ->issue_read() was called
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* in as we access the readahead_control struct.
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*/
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static ssize_t netfs_prepare_read_iterator(struct netfs_io_subrequest *subreq)
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{
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struct netfs_io_request *rreq = subreq->rreq;
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size_t rsize = subreq->len;
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if (subreq->source == NETFS_DOWNLOAD_FROM_SERVER)
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rsize = umin(rsize, rreq->io_streams[0].sreq_max_len);
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if (rreq->ractl) {
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/* If we don't have sufficient folios in the rolling buffer,
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* extract a folioq's worth from the readahead region at a time
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* into the buffer. Note that this acquires a ref on each page
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* that we will need to release later - but we don't want to do
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* that until after we've started the I/O.
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*/
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struct folio_batch put_batch;
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folio_batch_init(&put_batch);
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while (rreq->submitted < subreq->start + rsize) {
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struct folio_queue *tail = rreq->buffer_tail, *new;
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size_t added;
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new = kmalloc(sizeof(*new), GFP_NOFS);
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if (!new)
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return -ENOMEM;
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netfs_stat(&netfs_n_folioq);
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folioq_init(new);
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new->prev = tail;
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tail->next = new;
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rreq->buffer_tail = new;
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added = netfs_load_buffer_from_ra(rreq, new, &put_batch);
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rreq->iter.count += added;
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rreq->submitted += added;
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}
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folio_batch_release(&put_batch);
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}
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subreq->len = rsize;
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if (unlikely(rreq->io_streams[0].sreq_max_segs)) {
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size_t limit = netfs_limit_iter(&rreq->iter, 0, rsize,
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rreq->io_streams[0].sreq_max_segs);
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if (limit < rsize) {
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subreq->len = limit;
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trace_netfs_sreq(subreq, netfs_sreq_trace_limited);
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}
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}
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subreq->io_iter = rreq->iter;
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if (iov_iter_is_folioq(&subreq->io_iter)) {
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if (subreq->io_iter.folioq_slot >= folioq_nr_slots(subreq->io_iter.folioq)) {
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subreq->io_iter.folioq = subreq->io_iter.folioq->next;
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subreq->io_iter.folioq_slot = 0;
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}
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subreq->curr_folioq = (struct folio_queue *)subreq->io_iter.folioq;
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subreq->curr_folioq_slot = subreq->io_iter.folioq_slot;
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subreq->curr_folio_order = subreq->curr_folioq->orders[subreq->curr_folioq_slot];
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}
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iov_iter_truncate(&subreq->io_iter, subreq->len);
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iov_iter_advance(&rreq->iter, subreq->len);
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return subreq->len;
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}
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static enum netfs_io_source netfs_cache_prepare_read(struct netfs_io_request *rreq,
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struct netfs_io_subrequest *subreq,
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loff_t i_size)
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{
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struct netfs_cache_resources *cres = &rreq->cache_resources;
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if (!cres->ops)
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return NETFS_DOWNLOAD_FROM_SERVER;
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return cres->ops->prepare_read(subreq, i_size);
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}
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static void netfs_cache_read_terminated(void *priv, ssize_t transferred_or_error,
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bool was_async)
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{
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struct netfs_io_subrequest *subreq = priv;
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if (transferred_or_error < 0) {
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netfs_read_subreq_terminated(subreq, transferred_or_error, was_async);
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return;
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}
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if (transferred_or_error > 0)
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subreq->transferred += transferred_or_error;
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netfs_read_subreq_terminated(subreq, 0, was_async);
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}
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/*
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* Issue a read against the cache.
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* - Eats the caller's ref on subreq.
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*/
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static void netfs_read_cache_to_pagecache(struct netfs_io_request *rreq,
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struct netfs_io_subrequest *subreq)
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{
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struct netfs_cache_resources *cres = &rreq->cache_resources;
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netfs_stat(&netfs_n_rh_read);
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cres->ops->read(cres, subreq->start, &subreq->io_iter, NETFS_READ_HOLE_IGNORE,
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netfs_cache_read_terminated, subreq);
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}
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/*
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* Perform a read to the pagecache from a series of sources of different types,
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* slicing up the region to be read according to available cache blocks and
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* network rsize.
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*/
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static void netfs_read_to_pagecache(struct netfs_io_request *rreq)
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{
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struct netfs_inode *ictx = netfs_inode(rreq->inode);
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unsigned long long start = rreq->start;
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ssize_t size = rreq->len;
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int ret = 0;
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atomic_inc(&rreq->nr_outstanding);
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do {
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struct netfs_io_subrequest *subreq;
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enum netfs_io_source source = NETFS_DOWNLOAD_FROM_SERVER;
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ssize_t slice;
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subreq = netfs_alloc_subrequest(rreq);
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if (!subreq) {
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ret = -ENOMEM;
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break;
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}
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subreq->start = start;
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subreq->len = size;
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atomic_inc(&rreq->nr_outstanding);
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spin_lock_bh(&rreq->lock);
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list_add_tail(&subreq->rreq_link, &rreq->subrequests);
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subreq->prev_donated = rreq->prev_donated;
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rreq->prev_donated = 0;
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trace_netfs_sreq(subreq, netfs_sreq_trace_added);
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spin_unlock_bh(&rreq->lock);
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source = netfs_cache_prepare_read(rreq, subreq, rreq->i_size);
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subreq->source = source;
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if (source == NETFS_DOWNLOAD_FROM_SERVER) {
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unsigned long long zp = umin(ictx->zero_point, rreq->i_size);
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size_t len = subreq->len;
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if (subreq->start >= zp) {
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subreq->source = source = NETFS_FILL_WITH_ZEROES;
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goto fill_with_zeroes;
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}
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if (len > zp - subreq->start)
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len = zp - subreq->start;
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if (len == 0) {
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pr_err("ZERO-LEN READ: R=%08x[%x] l=%zx/%zx s=%llx z=%llx i=%llx",
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rreq->debug_id, subreq->debug_index,
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subreq->len, size,
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subreq->start, ictx->zero_point, rreq->i_size);
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break;
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}
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subreq->len = len;
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netfs_stat(&netfs_n_rh_download);
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if (rreq->netfs_ops->prepare_read) {
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ret = rreq->netfs_ops->prepare_read(subreq);
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if (ret < 0) {
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atomic_dec(&rreq->nr_outstanding);
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netfs_put_subrequest(subreq, false,
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netfs_sreq_trace_put_cancel);
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break;
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}
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trace_netfs_sreq(subreq, netfs_sreq_trace_prepare);
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}
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slice = netfs_prepare_read_iterator(subreq);
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if (slice < 0) {
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atomic_dec(&rreq->nr_outstanding);
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netfs_put_subrequest(subreq, false, netfs_sreq_trace_put_cancel);
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ret = slice;
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break;
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}
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rreq->netfs_ops->issue_read(subreq);
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goto done;
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}
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fill_with_zeroes:
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if (source == NETFS_FILL_WITH_ZEROES) {
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subreq->source = NETFS_FILL_WITH_ZEROES;
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trace_netfs_sreq(subreq, netfs_sreq_trace_submit);
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netfs_stat(&netfs_n_rh_zero);
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slice = netfs_prepare_read_iterator(subreq);
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__set_bit(NETFS_SREQ_CLEAR_TAIL, &subreq->flags);
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netfs_read_subreq_terminated(subreq, 0, false);
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goto done;
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}
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if (source == NETFS_READ_FROM_CACHE) {
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trace_netfs_sreq(subreq, netfs_sreq_trace_submit);
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slice = netfs_prepare_read_iterator(subreq);
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netfs_read_cache_to_pagecache(rreq, subreq);
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goto done;
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}
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pr_err("Unexpected read source %u\n", source);
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WARN_ON_ONCE(1);
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break;
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done:
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size -= slice;
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start += slice;
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cond_resched();
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} while (size > 0);
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if (atomic_dec_and_test(&rreq->nr_outstanding))
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netfs_rreq_terminated(rreq, false);
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/* Defer error return as we may need to wait for outstanding I/O. */
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cmpxchg(&rreq->error, 0, ret);
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}
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/*
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* Wait for the read operation to complete, successfully or otherwise.
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*/
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static int netfs_wait_for_read(struct netfs_io_request *rreq)
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{
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int ret;
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trace_netfs_rreq(rreq, netfs_rreq_trace_wait_ip);
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wait_on_bit(&rreq->flags, NETFS_RREQ_IN_PROGRESS, TASK_UNINTERRUPTIBLE);
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ret = rreq->error;
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if (ret == 0 && rreq->submitted < rreq->len) {
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trace_netfs_failure(rreq, NULL, ret, netfs_fail_short_read);
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ret = -EIO;
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}
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return ret;
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}
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/*
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* Set up the initial folioq of buffer folios in the rolling buffer and set the
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* iterator to refer to it.
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*/
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static int netfs_prime_buffer(struct netfs_io_request *rreq)
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{
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struct folio_queue *folioq;
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struct folio_batch put_batch;
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size_t added;
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folioq = kmalloc(sizeof(*folioq), GFP_KERNEL);
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if (!folioq)
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return -ENOMEM;
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netfs_stat(&netfs_n_folioq);
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folioq_init(folioq);
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rreq->buffer = folioq;
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rreq->buffer_tail = folioq;
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rreq->submitted = rreq->start;
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iov_iter_folio_queue(&rreq->iter, ITER_DEST, folioq, 0, 0, 0);
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folio_batch_init(&put_batch);
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added = netfs_load_buffer_from_ra(rreq, folioq, &put_batch);
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folio_batch_release(&put_batch);
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rreq->iter.count += added;
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rreq->submitted += added;
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return 0;
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}
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/**
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* netfs_readahead - Helper to manage a read request
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* @ractl: The description of the readahead request
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*
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* Fulfil a readahead request by drawing data from the cache if possible, or
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* the netfs if not. Space beyond the EOF is zero-filled. Multiple I/O
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* requests from different sources will get munged together. If necessary, the
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* readahead window can be expanded in either direction to a more convenient
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* alighment for RPC efficiency or to make storage in the cache feasible.
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*
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* The calling netfs must initialise a netfs context contiguous to the vfs
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* inode before calling this.
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*
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* This is usable whether or not caching is enabled.
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*/
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void netfs_readahead(struct readahead_control *ractl)
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{
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struct netfs_io_request *rreq;
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struct netfs_inode *ictx = netfs_inode(ractl->mapping->host);
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unsigned long long start = readahead_pos(ractl);
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size_t size = readahead_length(ractl);
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int ret;
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rreq = netfs_alloc_request(ractl->mapping, ractl->file, start, size,
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NETFS_READAHEAD);
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if (IS_ERR(rreq))
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return;
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ret = netfs_begin_cache_read(rreq, ictx);
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if (ret == -ENOMEM || ret == -EINTR || ret == -ERESTARTSYS)
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goto cleanup_free;
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netfs_stat(&netfs_n_rh_readahead);
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trace_netfs_read(rreq, readahead_pos(ractl), readahead_length(ractl),
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netfs_read_trace_readahead);
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netfs_rreq_expand(rreq, ractl);
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rreq->ractl = ractl;
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if (netfs_prime_buffer(rreq) < 0)
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goto cleanup_free;
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netfs_read_to_pagecache(rreq);
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netfs_put_request(rreq, true, netfs_rreq_trace_put_return);
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return;
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cleanup_free:
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netfs_put_request(rreq, false, netfs_rreq_trace_put_failed);
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return;
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}
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EXPORT_SYMBOL(netfs_readahead);
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/*
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* Create a rolling buffer with a single occupying folio.
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*/
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static int netfs_create_singular_buffer(struct netfs_io_request *rreq, struct folio *folio)
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{
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struct folio_queue *folioq;
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folioq = kmalloc(sizeof(*folioq), GFP_KERNEL);
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if (!folioq)
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return -ENOMEM;
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netfs_stat(&netfs_n_folioq);
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folioq_init(folioq);
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folioq_append(folioq, folio);
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BUG_ON(folioq_folio(folioq, 0) != folio);
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BUG_ON(folioq_folio_order(folioq, 0) != folio_order(folio));
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rreq->buffer = folioq;
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rreq->buffer_tail = folioq;
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rreq->submitted = rreq->start + rreq->len;
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iov_iter_folio_queue(&rreq->iter, ITER_DEST, folioq, 0, 0, rreq->len);
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rreq->ractl = (struct readahead_control *)1UL;
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return 0;
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}
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/*
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* Read into gaps in a folio partially filled by a streaming write.
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*/
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static int netfs_read_gaps(struct file *file, struct folio *folio)
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{
|
|
struct netfs_io_request *rreq;
|
|
struct address_space *mapping = folio->mapping;
|
|
struct netfs_folio *finfo = netfs_folio_info(folio);
|
|
struct netfs_inode *ctx = netfs_inode(mapping->host);
|
|
struct folio *sink = NULL;
|
|
struct bio_vec *bvec;
|
|
unsigned int from = finfo->dirty_offset;
|
|
unsigned int to = from + finfo->dirty_len;
|
|
unsigned int off = 0, i = 0;
|
|
size_t flen = folio_size(folio);
|
|
size_t nr_bvec = flen / PAGE_SIZE + 2;
|
|
size_t part;
|
|
int ret;
|
|
|
|
_enter("%lx", folio->index);
|
|
|
|
rreq = netfs_alloc_request(mapping, file, folio_pos(folio), flen, NETFS_READ_GAPS);
|
|
if (IS_ERR(rreq)) {
|
|
ret = PTR_ERR(rreq);
|
|
goto alloc_error;
|
|
}
|
|
|
|
ret = netfs_begin_cache_read(rreq, ctx);
|
|
if (ret == -ENOMEM || ret == -EINTR || ret == -ERESTARTSYS)
|
|
goto discard;
|
|
|
|
netfs_stat(&netfs_n_rh_read_folio);
|
|
trace_netfs_read(rreq, rreq->start, rreq->len, netfs_read_trace_read_gaps);
|
|
|
|
/* Fiddle the buffer so that a gap at the beginning and/or a gap at the
|
|
* end get copied to, but the middle is discarded.
|
|
*/
|
|
ret = -ENOMEM;
|
|
bvec = kmalloc_array(nr_bvec, sizeof(*bvec), GFP_KERNEL);
|
|
if (!bvec)
|
|
goto discard;
|
|
|
|
sink = folio_alloc(GFP_KERNEL, 0);
|
|
if (!sink) {
|
|
kfree(bvec);
|
|
goto discard;
|
|
}
|
|
|
|
trace_netfs_folio(folio, netfs_folio_trace_read_gaps);
|
|
|
|
rreq->direct_bv = bvec;
|
|
rreq->direct_bv_count = nr_bvec;
|
|
if (from > 0) {
|
|
bvec_set_folio(&bvec[i++], folio, from, 0);
|
|
off = from;
|
|
}
|
|
while (off < to) {
|
|
part = min_t(size_t, to - off, PAGE_SIZE);
|
|
bvec_set_folio(&bvec[i++], sink, part, 0);
|
|
off += part;
|
|
}
|
|
if (to < flen)
|
|
bvec_set_folio(&bvec[i++], folio, flen - to, to);
|
|
iov_iter_bvec(&rreq->iter, ITER_DEST, bvec, i, rreq->len);
|
|
rreq->submitted = rreq->start + flen;
|
|
|
|
netfs_read_to_pagecache(rreq);
|
|
|
|
if (sink)
|
|
folio_put(sink);
|
|
|
|
ret = netfs_wait_for_read(rreq);
|
|
if (ret == 0) {
|
|
flush_dcache_folio(folio);
|
|
folio_mark_uptodate(folio);
|
|
}
|
|
folio_unlock(folio);
|
|
netfs_put_request(rreq, false, netfs_rreq_trace_put_return);
|
|
return ret < 0 ? ret : 0;
|
|
|
|
discard:
|
|
netfs_put_request(rreq, false, netfs_rreq_trace_put_discard);
|
|
alloc_error:
|
|
folio_unlock(folio);
|
|
return ret;
|
|
}
|
|
|
|
/**
|
|
* netfs_read_folio - Helper to manage a read_folio request
|
|
* @file: The file to read from
|
|
* @folio: The folio to read
|
|
*
|
|
* Fulfil a read_folio 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 initialise a netfs context contiguous to the vfs
|
|
* inode before calling this.
|
|
*
|
|
* This is usable whether or not caching is enabled.
|
|
*/
|
|
int netfs_read_folio(struct file *file, struct folio *folio)
|
|
{
|
|
struct address_space *mapping = folio->mapping;
|
|
struct netfs_io_request *rreq;
|
|
struct netfs_inode *ctx = netfs_inode(mapping->host);
|
|
int ret;
|
|
|
|
if (folio_test_dirty(folio)) {
|
|
trace_netfs_folio(folio, netfs_folio_trace_read_gaps);
|
|
return netfs_read_gaps(file, folio);
|
|
}
|
|
|
|
_enter("%lx", folio->index);
|
|
|
|
rreq = netfs_alloc_request(mapping, file,
|
|
folio_pos(folio), folio_size(folio),
|
|
NETFS_READPAGE);
|
|
if (IS_ERR(rreq)) {
|
|
ret = PTR_ERR(rreq);
|
|
goto alloc_error;
|
|
}
|
|
|
|
ret = netfs_begin_cache_read(rreq, ctx);
|
|
if (ret == -ENOMEM || ret == -EINTR || ret == -ERESTARTSYS)
|
|
goto discard;
|
|
|
|
netfs_stat(&netfs_n_rh_read_folio);
|
|
trace_netfs_read(rreq, rreq->start, rreq->len, netfs_read_trace_readpage);
|
|
|
|
/* Set up the output buffer */
|
|
ret = netfs_create_singular_buffer(rreq, folio);
|
|
if (ret < 0)
|
|
goto discard;
|
|
|
|
netfs_read_to_pagecache(rreq);
|
|
ret = netfs_wait_for_read(rreq);
|
|
netfs_put_request(rreq, false, netfs_rreq_trace_put_return);
|
|
return ret < 0 ? ret : 0;
|
|
|
|
discard:
|
|
netfs_put_request(rreq, false, netfs_rreq_trace_put_discard);
|
|
alloc_error:
|
|
folio_unlock(folio);
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL(netfs_read_folio);
|
|
|
|
/*
|
|
* Prepare a folio for writing without reading first
|
|
* @folio: The folio being prepared
|
|
* @pos: starting position for the write
|
|
* @len: length of write
|
|
* @always_fill: T if the folio should always be completely filled/cleared
|
|
*
|
|
* In some cases, write_begin doesn't need to read at all:
|
|
* - full folio write
|
|
* - write that lies in a folio that is completely beyond EOF
|
|
* - write that covers the folio from start to EOF or beyond it
|
|
*
|
|
* If any of these criteria are met, then zero out the unwritten parts
|
|
* of the folio and return true. Otherwise, return false.
|
|
*/
|
|
static bool netfs_skip_folio_read(struct folio *folio, loff_t pos, size_t len,
|
|
bool always_fill)
|
|
{
|
|
struct inode *inode = folio_inode(folio);
|
|
loff_t i_size = i_size_read(inode);
|
|
size_t offset = offset_in_folio(folio, pos);
|
|
size_t plen = folio_size(folio);
|
|
|
|
if (unlikely(always_fill)) {
|
|
if (pos - offset + len <= i_size)
|
|
return false; /* Page entirely before EOF */
|
|
zero_user_segment(&folio->page, 0, plen);
|
|
folio_mark_uptodate(folio);
|
|
return true;
|
|
}
|
|
|
|
/* Full folio write */
|
|
if (offset == 0 && len >= plen)
|
|
return true;
|
|
|
|
/* Page entirely beyond the end of the file */
|
|
if (pos - offset >= i_size)
|
|
goto zero_out;
|
|
|
|
/* Write that covers from the start of the folio to EOF or beyond */
|
|
if (offset == 0 && (pos + len) >= i_size)
|
|
goto zero_out;
|
|
|
|
return false;
|
|
zero_out:
|
|
zero_user_segments(&folio->page, 0, offset, offset + len, plen);
|
|
return true;
|
|
}
|
|
|
|
/**
|
|
* netfs_write_begin - Helper to prepare for writing [DEPRECATED]
|
|
* @ctx: The netfs context
|
|
* @file: The file to read from
|
|
* @mapping: The mapping to read from
|
|
* @pos: File position at which the write will begin
|
|
* @len: The length of the write (may extend beyond the end of the folio chosen)
|
|
* @_folio: Where to put the resultant folio
|
|
* @_fsdata: Place for the netfs to store a cookie
|
|
*
|
|
* Pre-read data for a write-begin 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_read, is mandatory.
|
|
*
|
|
* The check_write_begin() operation can be provided to check for and flush
|
|
* conflicting writes once the folio is grabbed and locked. It is passed a
|
|
* pointer to the fsdata cookie that gets returned to the VM to be passed to
|
|
* write_end. It is permitted to sleep. It should return 0 if the request
|
|
* should go ahead or it may return an error. It may also unlock and put the
|
|
* folio, provided it sets ``*foliop`` to NULL, in which case a return of 0
|
|
* will cause the folio to be re-got and the process to be retried.
|
|
*
|
|
* The calling netfs must initialise a netfs context contiguous to the vfs
|
|
* inode before calling this.
|
|
*
|
|
* This is usable whether or not caching is enabled.
|
|
*
|
|
* Note that this should be considered deprecated and netfs_perform_write()
|
|
* used instead.
|
|
*/
|
|
int netfs_write_begin(struct netfs_inode *ctx,
|
|
struct file *file, struct address_space *mapping,
|
|
loff_t pos, unsigned int len, struct folio **_folio,
|
|
void **_fsdata)
|
|
{
|
|
struct netfs_io_request *rreq;
|
|
struct folio *folio;
|
|
pgoff_t index = pos >> PAGE_SHIFT;
|
|
int ret;
|
|
|
|
retry:
|
|
folio = __filemap_get_folio(mapping, index, FGP_WRITEBEGIN,
|
|
mapping_gfp_mask(mapping));
|
|
if (IS_ERR(folio))
|
|
return PTR_ERR(folio);
|
|
|
|
if (ctx->ops->check_write_begin) {
|
|
/* Allow the netfs (eg. ceph) to flush conflicts. */
|
|
ret = ctx->ops->check_write_begin(file, pos, len, &folio, _fsdata);
|
|
if (ret < 0) {
|
|
trace_netfs_failure(NULL, NULL, ret, netfs_fail_check_write_begin);
|
|
goto error;
|
|
}
|
|
if (!folio)
|
|
goto retry;
|
|
}
|
|
|
|
if (folio_test_uptodate(folio))
|
|
goto have_folio;
|
|
|
|
/* If the page is beyond the EOF, we want to clear it - unless it's
|
|
* within the cache granule containing the EOF, in which case we need
|
|
* to preload the granule.
|
|
*/
|
|
if (!netfs_is_cache_enabled(ctx) &&
|
|
netfs_skip_folio_read(folio, pos, len, false)) {
|
|
netfs_stat(&netfs_n_rh_write_zskip);
|
|
goto have_folio_no_wait;
|
|
}
|
|
|
|
rreq = netfs_alloc_request(mapping, file,
|
|
folio_pos(folio), folio_size(folio),
|
|
NETFS_READ_FOR_WRITE);
|
|
if (IS_ERR(rreq)) {
|
|
ret = PTR_ERR(rreq);
|
|
goto error;
|
|
}
|
|
rreq->no_unlock_folio = folio->index;
|
|
__set_bit(NETFS_RREQ_NO_UNLOCK_FOLIO, &rreq->flags);
|
|
|
|
ret = netfs_begin_cache_read(rreq, ctx);
|
|
if (ret == -ENOMEM || ret == -EINTR || ret == -ERESTARTSYS)
|
|
goto error_put;
|
|
|
|
netfs_stat(&netfs_n_rh_write_begin);
|
|
trace_netfs_read(rreq, pos, len, netfs_read_trace_write_begin);
|
|
|
|
/* Set up the output buffer */
|
|
ret = netfs_create_singular_buffer(rreq, folio);
|
|
if (ret < 0)
|
|
goto error_put;
|
|
|
|
netfs_read_to_pagecache(rreq);
|
|
ret = netfs_wait_for_read(rreq);
|
|
if (ret < 0)
|
|
goto error;
|
|
netfs_put_request(rreq, false, netfs_rreq_trace_put_return);
|
|
|
|
have_folio:
|
|
ret = folio_wait_private_2_killable(folio);
|
|
if (ret < 0)
|
|
goto error;
|
|
have_folio_no_wait:
|
|
*_folio = folio;
|
|
_leave(" = 0");
|
|
return 0;
|
|
|
|
error_put:
|
|
netfs_put_request(rreq, false, netfs_rreq_trace_put_failed);
|
|
error:
|
|
if (folio) {
|
|
folio_unlock(folio);
|
|
folio_put(folio);
|
|
}
|
|
_leave(" = %d", ret);
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL(netfs_write_begin);
|
|
|
|
/*
|
|
* Preload the data into a page we're proposing to write into.
|
|
*/
|
|
int netfs_prefetch_for_write(struct file *file, struct folio *folio,
|
|
size_t offset, size_t len)
|
|
{
|
|
struct netfs_io_request *rreq;
|
|
struct address_space *mapping = folio->mapping;
|
|
struct netfs_inode *ctx = netfs_inode(mapping->host);
|
|
unsigned long long start = folio_pos(folio);
|
|
size_t flen = folio_size(folio);
|
|
int ret;
|
|
|
|
_enter("%zx @%llx", flen, start);
|
|
|
|
ret = -ENOMEM;
|
|
|
|
rreq = netfs_alloc_request(mapping, file, start, flen,
|
|
NETFS_READ_FOR_WRITE);
|
|
if (IS_ERR(rreq)) {
|
|
ret = PTR_ERR(rreq);
|
|
goto error;
|
|
}
|
|
|
|
rreq->no_unlock_folio = folio->index;
|
|
__set_bit(NETFS_RREQ_NO_UNLOCK_FOLIO, &rreq->flags);
|
|
ret = netfs_begin_cache_read(rreq, ctx);
|
|
if (ret == -ENOMEM || ret == -EINTR || ret == -ERESTARTSYS)
|
|
goto error_put;
|
|
|
|
netfs_stat(&netfs_n_rh_write_begin);
|
|
trace_netfs_read(rreq, start, flen, netfs_read_trace_prefetch_for_write);
|
|
|
|
/* Set up the output buffer */
|
|
ret = netfs_create_singular_buffer(rreq, folio);
|
|
if (ret < 0)
|
|
goto error_put;
|
|
|
|
folioq_mark2(rreq->buffer, 0);
|
|
netfs_read_to_pagecache(rreq);
|
|
ret = netfs_wait_for_read(rreq);
|
|
netfs_put_request(rreq, false, netfs_rreq_trace_put_return);
|
|
return ret;
|
|
|
|
error_put:
|
|
netfs_put_request(rreq, false, netfs_rreq_trace_put_discard);
|
|
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);
|