Split fs/netfs/read_helper.c into two pieces, one to deal with buffered writes and one to deal with the I/O mechanism.
Changes ======= ver #2) - Add kdoc reference to new file. Signed-off-by: David Howells <dhowe...@redhat.com> Reviewed-by: Jeff Layton <jlay...@kernel.org> cc: linux-cachefs@redhat.com Link: https://lore.kernel.org/r/164623005586.3564931.6149556072728481767.st...@warthog.procyon.org.uk/ # v1 Link: https://lore.kernel.org/r/164678217075.1200972.5101072043126828757.st...@warthog.procyon.org.uk/ # v2 --- fs/netfs/Makefile | 1 fs/netfs/buffered_read.c | 428 ++++++++++++++++++++++++++++++++++++++++++++++ fs/netfs/io.c | 418 --------------------------------------------- 3 files changed, 429 insertions(+), 418 deletions(-) create mode 100644 fs/netfs/buffered_read.c diff --git a/fs/netfs/Makefile b/fs/netfs/Makefile index 51ece4f7bc77..88b904532bc7 100644 --- a/fs/netfs/Makefile +++ b/fs/netfs/Makefile @@ -1,6 +1,7 @@ # SPDX-License-Identifier: GPL-2.0 netfs-y := \ + buffered_read.o \ io.o \ objects.o diff --git a/fs/netfs/buffered_read.c b/fs/netfs/buffered_read.c new file mode 100644 index 000000000000..09ba7097a970 --- /dev/null +++ b/fs/netfs/buffered_read.c @@ -0,0 +1,428 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* Network filesystem high-level buffered read support. + * + * Copyright (C) 2021 Red Hat, Inc. All Rights Reserved. + * Written by David Howells (dhowe...@redhat.com) + */ + +#include <linux/export.h> +#include <linux/task_io_accounting_ops.h> +#include "internal.h" + +/* + * Unlock the folios in a read operation. We need to set PG_fscache on any + * folios we're going to write back before we unlock them. + */ +void netfs_rreq_unlock_folios(struct netfs_io_request *rreq) +{ + struct netfs_io_subrequest *subreq; + struct folio *folio; + unsigned int iopos, account = 0; + pgoff_t start_page = rreq->start / PAGE_SIZE; + pgoff_t last_page = ((rreq->start + rreq->len) / PAGE_SIZE) - 1; + bool subreq_failed = false; + + XA_STATE(xas, &rreq->mapping->i_pages, start_page); + + if (test_bit(NETFS_RREQ_FAILED, &rreq->flags)) { + __clear_bit(NETFS_RREQ_COPY_TO_CACHE, &rreq->flags); + list_for_each_entry(subreq, &rreq->subrequests, rreq_link) { + __clear_bit(NETFS_SREQ_COPY_TO_CACHE, &subreq->flags); + } + } + + /* Walk through the pagecache and the I/O request lists simultaneously. + * We may have a mixture of cached and uncached sections and we only + * really want to write out the uncached sections. This is slightly + * complicated by the possibility that we might have huge pages with a + * mixture inside. + */ + subreq = list_first_entry(&rreq->subrequests, + struct netfs_io_subrequest, rreq_link); + iopos = 0; + subreq_failed = (subreq->error < 0); + + trace_netfs_rreq(rreq, netfs_rreq_trace_unlock); + + rcu_read_lock(); + xas_for_each(&xas, folio, last_page) { + unsigned int pgpos = (folio_index(folio) - start_page) * PAGE_SIZE; + unsigned int pgend = pgpos + folio_size(folio); + bool pg_failed = false; + + for (;;) { + if (!subreq) { + pg_failed = true; + break; + } + if (test_bit(NETFS_SREQ_COPY_TO_CACHE, &subreq->flags)) + folio_start_fscache(folio); + pg_failed |= subreq_failed; + if (pgend < iopos + subreq->len) + break; + + account += subreq->transferred; + iopos += subreq->len; + if (!list_is_last(&subreq->rreq_link, &rreq->subrequests)) { + subreq = list_next_entry(subreq, rreq_link); + subreq_failed = (subreq->error < 0); + } else { + subreq = NULL; + subreq_failed = false; + } + if (pgend == iopos) + break; + } + + if (!pg_failed) { + flush_dcache_folio(folio); + folio_mark_uptodate(folio); + } + + if (!test_bit(NETFS_RREQ_DONT_UNLOCK_FOLIOS, &rreq->flags)) { + if (folio_index(folio) == rreq->no_unlock_folio && + test_bit(NETFS_RREQ_NO_UNLOCK_FOLIO, &rreq->flags)) + _debug("no unlock"); + else + folio_unlock(folio); + } + } + rcu_read_unlock(); + + task_io_account_read(account); + if (rreq->netfs_ops->done) + rreq->netfs_ops->done(rreq); +} + +static void netfs_cache_expand_readahead(struct netfs_io_request *rreq, + loff_t *_start, size_t *_len, loff_t i_size) +{ + struct netfs_cache_resources *cres = &rreq->cache_resources; + + if (cres->ops && cres->ops->expand_readahead) + cres->ops->expand_readahead(cres, _start, _len, i_size); +} + +static void netfs_rreq_expand(struct netfs_io_request *rreq, + struct readahead_control *ractl) +{ + /* Give the cache a chance to change the request parameters. The + * resultant request must contain the original region. + */ + netfs_cache_expand_readahead(rreq, &rreq->start, &rreq->len, rreq->i_size); + + /* Give the netfs a chance to change the request parameters. The + * resultant request must contain the original region. + */ + if (rreq->netfs_ops->expand_readahead) + rreq->netfs_ops->expand_readahead(rreq); + + /* Expand the request if the cache wants it to start earlier. Note + * that the expansion may get further extended if the VM wishes to + * insert THPs and the preferred start and/or end wind up in the middle + * of THPs. + * + * If this is the case, however, the THP size should be an integer + * multiple of the cache granule size, so we get a whole number of + * granules to deal with. + */ + if (rreq->start != readahead_pos(ractl) || + rreq->len != readahead_length(ractl)) { + readahead_expand(ractl, rreq->start, rreq->len); + rreq->start = readahead_pos(ractl); + rreq->len = readahead_length(ractl); + + trace_netfs_read(rreq, readahead_pos(ractl), readahead_length(ractl), + netfs_read_trace_expanded); + } +} + +/** + * netfs_readahead - Helper to manage a read request + * @ractl: The description of the readahead request + * + * Fulfil a readahead request by drawing data from the cache if possible, or + * the netfs if not. Space beyond the EOF is zero-filled. Multiple I/O + * requests from different sources will get munged together. If necessary, the + * readahead window can be expanded in either direction to a more convenient + * alighment for RPC efficiency or to make storage in the cache feasible. + * + * The calling netfs must initialise a netfs context contiguous to the vfs + * inode before calling this. + * + * This is usable whether or not caching is enabled. + */ +void netfs_readahead(struct readahead_control *ractl) +{ + struct netfs_io_request *rreq; + struct netfs_i_context *ctx = netfs_i_context(ractl->mapping->host); + int ret; + + _enter("%lx,%x", readahead_index(ractl), readahead_count(ractl)); + + if (readahead_count(ractl) == 0) + return; + + rreq = netfs_alloc_request(ractl->mapping, ractl->file, + readahead_pos(ractl), + readahead_length(ractl), + NETFS_READAHEAD); + if (IS_ERR(rreq)) + return; + + if (ctx->ops->begin_cache_operation) { + ret = ctx->ops->begin_cache_operation(rreq); + if (ret == -ENOMEM || ret == -EINTR || ret == -ERESTARTSYS) + goto cleanup_free; + } + + netfs_stat(&netfs_n_rh_readahead); + trace_netfs_read(rreq, readahead_pos(ractl), readahead_length(ractl), + netfs_read_trace_readahead); + + netfs_rreq_expand(rreq, ractl); + + /* Drop the refs on the folios here rather than in the cache or + * filesystem. The locks will be dropped in netfs_rreq_unlock(). + */ + while (readahead_folio(ractl)) + ; + + netfs_begin_read(rreq, false); + return; + +cleanup_free: + netfs_put_request(rreq, false, netfs_rreq_trace_put_failed); + return; +} +EXPORT_SYMBOL(netfs_readahead); + +/** + * netfs_readpage - Helper to manage a readpage request + * @file: The file to read from + * @subpage: A subpage of the folio to read + * + * Fulfil a readpage request by drawing data from the cache if possible, or the + * netfs if not. Space beyond the EOF is zero-filled. Multiple I/O requests + * from different sources will get munged together. + * + * The calling netfs must initialise a netfs context contiguous to the vfs + * inode before calling this. + * + * This is usable whether or not caching is enabled. + */ +int netfs_readpage(struct file *file, struct page *subpage) +{ + struct folio *folio = page_folio(subpage); + struct address_space *mapping = folio_file_mapping(folio); + struct netfs_io_request *rreq; + struct netfs_i_context *ctx = netfs_i_context(mapping->host); + int ret; + + _enter("%lx", folio_index(folio)); + + rreq = netfs_alloc_request(mapping, file, + folio_file_pos(folio), folio_size(folio), + NETFS_READPAGE); + if (IS_ERR(rreq)) { + ret = PTR_ERR(rreq); + goto alloc_error; + } + + if (ctx->ops->begin_cache_operation) { + ret = ctx->ops->begin_cache_operation(rreq); + if (ret == -ENOMEM || ret == -EINTR || ret == -ERESTARTSYS) + goto discard; + } + + netfs_stat(&netfs_n_rh_readpage); + trace_netfs_read(rreq, rreq->start, rreq->len, netfs_read_trace_readpage); + return netfs_begin_read(rreq, true); + +discard: + netfs_put_request(rreq, false, netfs_rreq_trace_put_discard); +alloc_error: + folio_unlock(folio); + return ret; +} +EXPORT_SYMBOL(netfs_readpage); + +/* + * 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, len); + return true; +} + +/** + * netfs_write_begin - Helper to prepare for writing + * @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) + * @aop_flags: AOP_* flags + * @_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. If + * necessary, the readahead window can be expanded in either direction to a + * more convenient alighment for RPC efficiency or to make storage in the cache + * feasible. + * + * The calling netfs must provide a table of operations, only one of which, + * issue_op, is mandatory. + * + * 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; unlock the folio and return -EAGAIN to cause the folio to + * be regot; or return an error. + * + * 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_write_begin(struct file *file, struct address_space *mapping, + loff_t pos, unsigned int len, unsigned int aop_flags, + struct folio **_folio, void **_fsdata) +{ + struct netfs_io_request *rreq; + struct netfs_i_context *ctx = netfs_i_context(file_inode(file )); + struct folio *folio; + unsigned int fgp_flags; + pgoff_t index = pos >> PAGE_SHIFT; + int ret; + + DEFINE_READAHEAD(ractl, file, NULL, mapping, index); + +retry: + fgp_flags = FGP_LOCK | FGP_WRITE | FGP_CREAT | FGP_STABLE; + if (aop_flags & AOP_FLAG_NOFS) + fgp_flags |= FGP_NOFS; + folio = __filemap_get_folio(mapping, index, fgp_flags, + mapping_gfp_mask(mapping)); + if (!folio) + return -ENOMEM; + + 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); + if (ret == -EAGAIN) + goto retry; + goto error; + } + } + + 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_file_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(folio); + __set_bit(NETFS_RREQ_NO_UNLOCK_FOLIO, &rreq->flags); + + if (ctx->ops->begin_cache_operation) { + ret = ctx->ops->begin_cache_operation(rreq); + 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); + + /* Expand the request to meet caching requirements and download + * preferences. + */ + ractl._nr_pages = folio_nr_pages(folio); + netfs_rreq_expand(rreq, &ractl); + + /* We hold the folio locks, so we can drop the references */ + folio_get(folio); + while (readahead_folio(&ractl)) + ; + + ret = netfs_begin_read(rreq, true); + if (ret < 0) + goto error; + +have_folio: + ret = folio_wait_fscache_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: + folio_unlock(folio); + folio_put(folio); + _leave(" = %d", ret); + return ret; +} +EXPORT_SYMBOL(netfs_write_begin); diff --git a/fs/netfs/io.c b/fs/netfs/io.c index d448dc4f1010..6d43f9ea1b5a 100644 --- a/fs/netfs/io.c +++ b/fs/netfs/io.c @@ -246,91 +246,6 @@ static void netfs_rreq_write_to_cache(struct netfs_io_request *rreq) BUG(); } -/* - * Unlock the folios in a read operation. We need to set PG_fscache on any - * folios we're going to write back before we unlock them. - */ -void netfs_rreq_unlock_folios(struct netfs_io_request *rreq) -{ - struct netfs_io_subrequest *subreq; - struct folio *folio; - unsigned int iopos, account = 0; - pgoff_t start_page = rreq->start / PAGE_SIZE; - pgoff_t last_page = ((rreq->start + rreq->len) / PAGE_SIZE) - 1; - bool subreq_failed = false; - - XA_STATE(xas, &rreq->mapping->i_pages, start_page); - - if (test_bit(NETFS_RREQ_FAILED, &rreq->flags)) { - __clear_bit(NETFS_RREQ_COPY_TO_CACHE, &rreq->flags); - list_for_each_entry(subreq, &rreq->subrequests, rreq_link) { - __clear_bit(NETFS_SREQ_COPY_TO_CACHE, &subreq->flags); - } - } - - /* Walk through the pagecache and the I/O request lists simultaneously. - * We may have a mixture of cached and uncached sections and we only - * really want to write out the uncached sections. This is slightly - * complicated by the possibility that we might have huge pages with a - * mixture inside. - */ - subreq = list_first_entry(&rreq->subrequests, - struct netfs_io_subrequest, rreq_link); - iopos = 0; - subreq_failed = (subreq->error < 0); - - trace_netfs_rreq(rreq, netfs_rreq_trace_unlock); - - rcu_read_lock(); - xas_for_each(&xas, folio, last_page) { - unsigned int pgpos = (folio_index(folio) - start_page) * PAGE_SIZE; - unsigned int pgend = pgpos + folio_size(folio); - bool pg_failed = false; - - for (;;) { - if (!subreq) { - pg_failed = true; - break; - } - if (test_bit(NETFS_SREQ_COPY_TO_CACHE, &subreq->flags)) - folio_start_fscache(folio); - pg_failed |= subreq_failed; - if (pgend < iopos + subreq->len) - break; - - account += subreq->transferred; - iopos += subreq->len; - if (!list_is_last(&subreq->rreq_link, &rreq->subrequests)) { - subreq = list_next_entry(subreq, rreq_link); - subreq_failed = (subreq->error < 0); - } else { - subreq = NULL; - subreq_failed = false; - } - if (pgend == iopos) - break; - } - - if (!pg_failed) { - flush_dcache_folio(folio); - folio_mark_uptodate(folio); - } - - if (!test_bit(NETFS_RREQ_DONT_UNLOCK_FOLIOS, &rreq->flags)) { - if (folio_index(folio) == rreq->no_unlock_folio && - test_bit(NETFS_RREQ_NO_UNLOCK_FOLIO, &rreq->flags)) - _debug("no unlock"); - else - folio_unlock(folio); - } - } - rcu_read_unlock(); - - task_io_account_read(account); - if (rreq->netfs_ops->done) - rreq->netfs_ops->done(rreq); -} - /* * Handle a short read. */ @@ -750,336 +665,3 @@ int netfs_begin_read(struct netfs_io_request *rreq, bool sync) } return ret; } - -static void netfs_cache_expand_readahead(struct netfs_io_request *rreq, - loff_t *_start, size_t *_len, loff_t i_size) -{ - struct netfs_cache_resources *cres = &rreq->cache_resources; - - if (cres->ops && cres->ops->expand_readahead) - cres->ops->expand_readahead(cres, _start, _len, i_size); -} - -static void netfs_rreq_expand(struct netfs_io_request *rreq, - struct readahead_control *ractl) -{ - /* Give the cache a chance to change the request parameters. The - * resultant request must contain the original region. - */ - netfs_cache_expand_readahead(rreq, &rreq->start, &rreq->len, rreq->i_size); - - /* Give the netfs a chance to change the request parameters. The - * resultant request must contain the original region. - */ - if (rreq->netfs_ops->expand_readahead) - rreq->netfs_ops->expand_readahead(rreq); - - /* Expand the request if the cache wants it to start earlier. Note - * that the expansion may get further extended if the VM wishes to - * insert THPs and the preferred start and/or end wind up in the middle - * of THPs. - * - * If this is the case, however, the THP size should be an integer - * multiple of the cache granule size, so we get a whole number of - * granules to deal with. - */ - if (rreq->start != readahead_pos(ractl) || - rreq->len != readahead_length(ractl)) { - readahead_expand(ractl, rreq->start, rreq->len); - rreq->start = readahead_pos(ractl); - rreq->len = readahead_length(ractl); - - trace_netfs_read(rreq, readahead_pos(ractl), readahead_length(ractl), - netfs_read_trace_expanded); - } -} - -/** - * netfs_readahead - Helper to manage a read request - * @ractl: The description of the readahead request - * - * Fulfil a readahead request by drawing data from the cache if possible, or - * the netfs if not. Space beyond the EOF is zero-filled. Multiple I/O - * requests from different sources will get munged together. If necessary, the - * readahead window can be expanded in either direction to a more convenient - * alighment for RPC efficiency or to make storage in the cache feasible. - * - * The calling netfs must initialise a netfs context contiguous to the vfs - * inode before calling this. - * - * This is usable whether or not caching is enabled. - */ -void netfs_readahead(struct readahead_control *ractl) -{ - struct netfs_io_request *rreq; - struct netfs_i_context *ctx = netfs_i_context(ractl->mapping->host); - int ret; - - _enter("%lx,%x", readahead_index(ractl), readahead_count(ractl)); - - if (readahead_count(ractl) == 0) - return; - - rreq = netfs_alloc_request(ractl->mapping, ractl->file, - readahead_pos(ractl), - readahead_length(ractl), - NETFS_READAHEAD); - if (IS_ERR(rreq)) - return; - - if (ctx->ops->begin_cache_operation) { - ret = ctx->ops->begin_cache_operation(rreq); - if (ret == -ENOMEM || ret == -EINTR || ret == -ERESTARTSYS) - goto cleanup_free; - } - - netfs_stat(&netfs_n_rh_readahead); - trace_netfs_read(rreq, readahead_pos(ractl), readahead_length(ractl), - netfs_read_trace_readahead); - - netfs_rreq_expand(rreq, ractl); - - /* Drop the refs on the folios here rather than in the cache or - * filesystem. The locks will be dropped in netfs_rreq_unlock(). - */ - while (readahead_folio(ractl)) - ; - - netfs_begin_read(rreq, false); - return; - -cleanup_free: - netfs_put_request(rreq, false, netfs_rreq_trace_put_failed); - return; -} -EXPORT_SYMBOL(netfs_readahead); - -/** - * netfs_readpage - Helper to manage a readpage request - * @file: The file to read from - * @subpage: A subpage of the folio to read - * - * Fulfil a readpage request by drawing data from the cache if possible, or the - * netfs if not. Space beyond the EOF is zero-filled. Multiple I/O requests - * from different sources will get munged together. - * - * The calling netfs must initialise a netfs context contiguous to the vfs - * inode before calling this. - * - * This is usable whether or not caching is enabled. - */ -int netfs_readpage(struct file *file, struct page *subpage) -{ - struct folio *folio = page_folio(subpage); - struct address_space *mapping = folio->mapping; - struct netfs_io_request *rreq; - struct netfs_i_context *ctx = netfs_i_context(mapping->host); - int ret; - - _enter("%lx", folio_index(folio)); - - rreq = netfs_alloc_request(mapping, file, - folio_file_pos(folio), folio_size(folio), - NETFS_READPAGE); - if (IS_ERR(rreq)) { - ret = PTR_ERR(rreq); - goto alloc_error; - } - - if (ctx->ops->begin_cache_operation) { - ret = ctx->ops->begin_cache_operation(rreq); - if (ret == -ENOMEM || ret == -EINTR || ret == -ERESTARTSYS) - goto discard; - } - - netfs_stat(&netfs_n_rh_readpage); - trace_netfs_read(rreq, rreq->start, rreq->len, netfs_read_trace_readpage); - return netfs_begin_read(rreq, true); - -discard: - netfs_put_request(rreq, false, netfs_rreq_trace_put_discard); -alloc_error: - folio_unlock(folio); - return ret; -} -EXPORT_SYMBOL(netfs_readpage); - -/* - * 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, len); - return true; -} - -/** - * netfs_write_begin - Helper to prepare for writing - * @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) - * @aop_flags: AOP_* flags - * @_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. If - * necessary, the readahead window can be expanded in either direction to a - * more convenient alighment for RPC efficiency or to make storage in the cache - * feasible. - * - * The calling netfs must provide a table of operations, only one of which, - * issue_op, is mandatory. - * - * 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; unlock the folio and return -EAGAIN to cause the folio to - * be regot; or return an error. - * - * 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_write_begin(struct file *file, struct address_space *mapping, - loff_t pos, unsigned int len, unsigned int aop_flags, - struct folio **_folio, void **_fsdata) -{ - struct netfs_io_request *rreq; - struct netfs_i_context *ctx = netfs_i_context(file_inode(file )); - struct folio *folio; - unsigned int fgp_flags; - pgoff_t index = pos >> PAGE_SHIFT; - int ret; - - DEFINE_READAHEAD(ractl, file, NULL, mapping, index); - -retry: - fgp_flags = FGP_LOCK | FGP_WRITE | FGP_CREAT | FGP_STABLE; - if (aop_flags & AOP_FLAG_NOFS) - fgp_flags |= FGP_NOFS; - folio = __filemap_get_folio(mapping, index, fgp_flags, - mapping_gfp_mask(mapping)); - if (!folio) - return -ENOMEM; - - 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); - if (ret == -EAGAIN) - goto retry; - goto error; - } - } - - 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_file_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(folio); - __set_bit(NETFS_RREQ_NO_UNLOCK_FOLIO, &rreq->flags); - - if (ctx->ops->begin_cache_operation) { - ret = ctx->ops->begin_cache_operation(rreq); - 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); - - /* Expand the request to meet caching requirements and download - * preferences. - */ - ractl._nr_pages = folio_nr_pages(folio); - netfs_rreq_expand(rreq, &ractl); - - /* We hold the folio locks, so we can drop the references */ - folio_get(folio); - while (readahead_folio(&ractl)) - ; - - ret = netfs_begin_read(rreq, true); - if (ret < 0) - goto error; - -have_folio: - ret = folio_wait_fscache_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: - folio_unlock(folio); - folio_put(folio); - _leave(" = %d", ret); - return ret; -} -EXPORT_SYMBOL(netfs_write_begin); -- Linux-cachefs mailing list Linux-cachefs@redhat.com https://listman.redhat.com/mailman/listinfo/linux-cachefs
