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427 lines
13 KiB
427 lines
13 KiB
// 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 ([email protected]) |
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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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/* |
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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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unsigned int iopos, account = 0; |
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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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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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|
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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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iopos = 0; |
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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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unsigned int pgpos = (folio_index(folio) - start_page) * PAGE_SIZE; |
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unsigned int pgend = pgpos + folio_size(folio); |
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bool pg_failed = false; |
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for (;;) { |
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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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if (pgend < iopos + subreq->len) |
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break; |
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account += subreq->transferred; |
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iopos += subreq->len; |
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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 (pgend == iopos) |
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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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|
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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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unsigned int fgp_flags = FGP_LOCK | FGP_WRITE | FGP_CREAT | FGP_STABLE; |
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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_flags, |
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mapping_gfp_mask(mapping)); |
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if (!folio) |
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return -ENOMEM; |
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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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