433 lines
13 KiB
C
433 lines
13 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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/*
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* Unlock the folios in a read operation. We need to set PG_fscache on any
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* folios we're going to write back before we unlock them.
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*/
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void netfs_rreq_unlock_folios(struct netfs_io_request *rreq)
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{
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struct netfs_io_subrequest *subreq;
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struct folio *folio;
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pgoff_t start_page = rreq->start / PAGE_SIZE;
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pgoff_t last_page = ((rreq->start + rreq->len) / PAGE_SIZE) - 1;
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size_t account = 0;
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bool subreq_failed = false;
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XA_STATE(xas, &rreq->mapping->i_pages, start_page);
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if (test_bit(NETFS_RREQ_FAILED, &rreq->flags)) {
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__clear_bit(NETFS_RREQ_COPY_TO_CACHE, &rreq->flags);
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list_for_each_entry(subreq, &rreq->subrequests, rreq_link) {
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__clear_bit(NETFS_SREQ_COPY_TO_CACHE, &subreq->flags);
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}
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}
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/* Walk through the pagecache and the I/O request lists simultaneously.
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* We may have a mixture of cached and uncached sections and we only
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* really want to write out the uncached sections. This is slightly
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* complicated by the possibility that we might have huge pages with a
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* mixture inside.
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*/
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subreq = list_first_entry(&rreq->subrequests,
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struct netfs_io_subrequest, rreq_link);
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subreq_failed = (subreq->error < 0);
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trace_netfs_rreq(rreq, netfs_rreq_trace_unlock);
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rcu_read_lock();
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xas_for_each(&xas, folio, last_page) {
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loff_t pg_end;
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bool pg_failed = false;
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if (xas_retry(&xas, folio))
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continue;
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pg_end = folio_pos(folio) + folio_size(folio) - 1;
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for (;;) {
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loff_t sreq_end;
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if (!subreq) {
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pg_failed = true;
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break;
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}
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if (test_bit(NETFS_SREQ_COPY_TO_CACHE, &subreq->flags))
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folio_start_fscache(folio);
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pg_failed |= subreq_failed;
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sreq_end = subreq->start + subreq->len - 1;
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if (pg_end < sreq_end)
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break;
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account += subreq->transferred;
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if (!list_is_last(&subreq->rreq_link, &rreq->subrequests)) {
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subreq = list_next_entry(subreq, rreq_link);
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subreq_failed = (subreq->error < 0);
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} else {
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subreq = NULL;
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subreq_failed = false;
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}
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if (pg_end == sreq_end)
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break;
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}
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if (!pg_failed) {
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flush_dcache_folio(folio);
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folio_mark_uptodate(folio);
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}
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if (!test_bit(NETFS_RREQ_DONT_UNLOCK_FOLIOS, &rreq->flags)) {
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if (folio_index(folio) == rreq->no_unlock_folio &&
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test_bit(NETFS_RREQ_NO_UNLOCK_FOLIO, &rreq->flags))
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_debug("no unlock");
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else
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folio_unlock(folio);
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}
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}
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rcu_read_unlock();
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task_io_account_read(account);
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if (rreq->netfs_ops->done)
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rreq->netfs_ops->done(rreq);
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}
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static void netfs_cache_expand_readahead(struct netfs_io_request *rreq,
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loff_t *_start, size_t *_len, 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 && 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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* 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 *ctx = netfs_inode(ractl->mapping->host);
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int ret;
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_enter("%lx,%x", readahead_index(ractl), readahead_count(ractl));
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if (readahead_count(ractl) == 0)
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return;
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rreq = netfs_alloc_request(ractl->mapping, ractl->file,
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readahead_pos(ractl),
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readahead_length(ractl),
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NETFS_READAHEAD);
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if (IS_ERR(rreq))
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return;
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if (ctx->ops->begin_cache_operation) {
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ret = ctx->ops->begin_cache_operation(rreq);
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if (ret == -ENOMEM || ret == -EINTR || ret == -ERESTARTSYS)
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goto cleanup_free;
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}
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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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/* Drop the refs on the folios here rather than in the cache or
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* filesystem. The locks will be dropped in netfs_rreq_unlock().
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*/
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while (readahead_folio(ractl))
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;
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netfs_begin_read(rreq, false);
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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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* netfs_read_folio - Helper to manage a read_folio request
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* @file: The file to read from
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* @folio: The folio to read
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*
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* Fulfil a read_folio request by drawing data from the cache if
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* possible, or the netfs if not. Space beyond the EOF is zero-filled.
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* Multiple I/O requests from different sources will get munged together.
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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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int netfs_read_folio(struct file *file, struct folio *folio)
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{
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struct address_space *mapping = folio_file_mapping(folio);
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struct netfs_io_request *rreq;
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struct netfs_inode *ctx = netfs_inode(mapping->host);
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int ret;
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_enter("%lx", folio_index(folio));
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rreq = netfs_alloc_request(mapping, file,
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folio_file_pos(folio), folio_size(folio),
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NETFS_READPAGE);
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if (IS_ERR(rreq)) {
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ret = PTR_ERR(rreq);
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goto alloc_error;
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}
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if (ctx->ops->begin_cache_operation) {
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ret = ctx->ops->begin_cache_operation(rreq);
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if (ret == -ENOMEM || ret == -EINTR || ret == -ERESTARTSYS)
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goto discard;
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}
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netfs_stat(&netfs_n_rh_readpage);
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trace_netfs_read(rreq, rreq->start, rreq->len, netfs_read_trace_readpage);
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return netfs_begin_read(rreq, true);
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discard:
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netfs_put_request(rreq, false, netfs_rreq_trace_put_discard);
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alloc_error:
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folio_unlock(folio);
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return ret;
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}
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EXPORT_SYMBOL(netfs_read_folio);
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/*
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* Prepare a folio for writing without reading first
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* @folio: The folio being prepared
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* @pos: starting position for the write
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* @len: length of write
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* @always_fill: T if the folio should always be completely filled/cleared
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*
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* In some cases, write_begin doesn't need to read at all:
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* - full folio write
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* - write that lies in a folio that is completely beyond EOF
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* - write that covers the folio from start to EOF or beyond it
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*
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* If any of these criteria are met, then zero out the unwritten parts
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* of the folio and return true. Otherwise, return false.
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*/
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static bool netfs_skip_folio_read(struct folio *folio, loff_t pos, size_t len,
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bool always_fill)
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{
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struct inode *inode = folio_inode(folio);
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loff_t i_size = i_size_read(inode);
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size_t offset = offset_in_folio(folio, pos);
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size_t plen = folio_size(folio);
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if (unlikely(always_fill)) {
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if (pos - offset + len <= i_size)
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return false; /* Page entirely before EOF */
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zero_user_segment(&folio->page, 0, plen);
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folio_mark_uptodate(folio);
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return true;
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}
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/* Full folio write */
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if (offset == 0 && len >= plen)
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return true;
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/* Page entirely beyond the end of the file */
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if (pos - offset >= i_size)
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goto zero_out;
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/* Write that covers from the start of the folio to EOF or beyond */
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if (offset == 0 && (pos + len) >= i_size)
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goto zero_out;
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return false;
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zero_out:
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zero_user_segments(&folio->page, 0, offset, offset + len, plen);
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return true;
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}
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/**
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* netfs_write_begin - Helper to prepare for writing
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* @ctx: The netfs context
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* @file: The file to read from
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* @mapping: The mapping to read from
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* @pos: File position at which the write will begin
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* @len: The length of the write (may extend beyond the end of the folio chosen)
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* @_folio: Where to put the resultant folio
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* @_fsdata: Place for the netfs to store a cookie
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*
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* Pre-read data for a write-begin request by drawing data from the cache if
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* possible, or the netfs if not. Space beyond the EOF is zero-filled.
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* Multiple I/O requests from different sources will get munged together. If
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* necessary, the readahead window can be expanded in either direction to a
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* more convenient alighment for RPC efficiency or to make storage in the cache
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* feasible.
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*
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* The calling netfs must provide a table of operations, only one of which,
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* issue_op, is mandatory.
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*
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* The check_write_begin() operation can be provided to check for and flush
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* conflicting writes once the folio is grabbed and locked. It is passed a
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* pointer to the fsdata cookie that gets returned to the VM to be passed to
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* write_end. It is permitted to sleep. It should return 0 if the request
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* should go ahead or it may return an error. It may also unlock and put the
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* folio, provided it sets ``*foliop`` to NULL, in which case a return of 0
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* will cause the folio to be re-got and the process to be retried.
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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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int netfs_write_begin(struct netfs_inode *ctx,
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struct file *file, struct address_space *mapping,
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loff_t pos, unsigned int len, struct folio **_folio,
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void **_fsdata)
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{
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struct netfs_io_request *rreq;
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struct folio *folio;
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pgoff_t index = pos >> PAGE_SHIFT;
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int ret;
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DEFINE_READAHEAD(ractl, file, NULL, mapping, index);
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retry:
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folio = __filemap_get_folio(mapping, index, FGP_WRITEBEGIN,
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mapping_gfp_mask(mapping));
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if (IS_ERR(folio))
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return PTR_ERR(folio);
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if (ctx->ops->check_write_begin) {
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/* Allow the netfs (eg. ceph) to flush conflicts. */
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ret = ctx->ops->check_write_begin(file, pos, len, &folio, _fsdata);
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if (ret < 0) {
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trace_netfs_failure(NULL, NULL, ret, netfs_fail_check_write_begin);
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goto error;
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}
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if (!folio)
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goto retry;
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}
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if (folio_test_uptodate(folio))
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goto have_folio;
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/* If the page is beyond the EOF, we want to clear it - unless it's
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* within the cache granule containing the EOF, in which case we need
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* to preload the granule.
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*/
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if (!netfs_is_cache_enabled(ctx) &&
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netfs_skip_folio_read(folio, pos, len, false)) {
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netfs_stat(&netfs_n_rh_write_zskip);
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goto have_folio_no_wait;
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}
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rreq = netfs_alloc_request(mapping, file,
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folio_file_pos(folio), folio_size(folio),
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NETFS_READ_FOR_WRITE);
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if (IS_ERR(rreq)) {
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ret = PTR_ERR(rreq);
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goto error;
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}
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rreq->no_unlock_folio = folio_index(folio);
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__set_bit(NETFS_RREQ_NO_UNLOCK_FOLIO, &rreq->flags);
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if (ctx->ops->begin_cache_operation) {
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ret = ctx->ops->begin_cache_operation(rreq);
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if (ret == -ENOMEM || ret == -EINTR || ret == -ERESTARTSYS)
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goto error_put;
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}
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netfs_stat(&netfs_n_rh_write_begin);
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trace_netfs_read(rreq, pos, len, netfs_read_trace_write_begin);
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/* Expand the request to meet caching requirements and download
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* preferences.
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*/
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ractl._nr_pages = folio_nr_pages(folio);
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netfs_rreq_expand(rreq, &ractl);
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/* We hold the folio locks, so we can drop the references */
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folio_get(folio);
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while (readahead_folio(&ractl))
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;
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ret = netfs_begin_read(rreq, true);
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if (ret < 0)
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goto error;
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have_folio:
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ret = folio_wait_fscache_killable(folio);
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if (ret < 0)
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goto error;
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have_folio_no_wait:
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*_folio = folio;
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_leave(" = 0");
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return 0;
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error_put:
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netfs_put_request(rreq, false, netfs_rreq_trace_put_failed);
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error:
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if (folio) {
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folio_unlock(folio);
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folio_put(folio);
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}
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_leave(" = %d", ret);
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return ret;
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}
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EXPORT_SYMBOL(netfs_write_begin);
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