diff options
Diffstat (limited to 'fs/netfs/buffered_read.c')
| -rw-r--r-- | fs/netfs/buffered_read.c | 834 |
1 files changed, 834 insertions, 0 deletions
diff --git a/fs/netfs/buffered_read.c b/fs/netfs/buffered_read.c new file mode 100644 index 000000000000..37ab6f28b5ad --- /dev/null +++ b/fs/netfs/buffered_read.c @@ -0,0 +1,834 @@ +// 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 (dhowells@redhat.com) + */ + +#include <linux/export.h> +#include <linux/task_io_accounting_ops.h> +#include "internal.h" + +static void netfs_cache_expand_readahead(struct netfs_io_request *rreq, + unsigned long long *_start, + unsigned long long *_len, + unsigned long long 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); + } +} + +/* + * Begin an operation, and fetch the stored zero point value from the cookie if + * available. + */ +static int netfs_begin_cache_read(struct netfs_io_request *rreq, struct netfs_inode *ctx) +{ + return fscache_begin_read_operation(&rreq->cache_resources, netfs_i_cookie(ctx)); +} + +/* + * netfs_prepare_read_iterator - Prepare the subreq iterator for I/O + * @subreq: The subrequest to be set up + * + * Prepare the I/O iterator representing the read buffer on a subrequest for + * the filesystem to use for I/O (it can be passed directly to a socket). This + * is intended to be called from the ->issue_read() method once the filesystem + * has trimmed the request to the size it wants. + * + * Returns the limited size if successful and -ENOMEM if insufficient memory + * available. + * + * [!] NOTE: This must be run in the same thread as ->issue_read() was called + * in as we access the readahead_control struct. + */ +static ssize_t netfs_prepare_read_iterator(struct netfs_io_subrequest *subreq, + struct readahead_control *ractl) +{ + struct netfs_io_request *rreq = subreq->rreq; + size_t rsize = subreq->len; + + if (subreq->source == NETFS_DOWNLOAD_FROM_SERVER) + rsize = umin(rsize, rreq->io_streams[0].sreq_max_len); + + if (ractl) { + /* If we don't have sufficient folios in the rolling buffer, + * extract a folioq's worth from the readahead region at a time + * into the buffer. Note that this acquires a ref on each page + * that we will need to release later - but we don't want to do + * that until after we've started the I/O. + */ + struct folio_batch put_batch; + + folio_batch_init(&put_batch); + while (rreq->submitted < subreq->start + rsize) { + ssize_t added; + + added = rolling_buffer_load_from_ra(&rreq->buffer, ractl, + &put_batch); + if (added < 0) + return added; + rreq->submitted += added; + } + folio_batch_release(&put_batch); + } + + subreq->len = rsize; + if (unlikely(rreq->io_streams[0].sreq_max_segs)) { + size_t limit = netfs_limit_iter(&rreq->buffer.iter, 0, rsize, + rreq->io_streams[0].sreq_max_segs); + + if (limit < rsize) { + subreq->len = limit; + trace_netfs_sreq(subreq, netfs_sreq_trace_limited); + } + } + + subreq->io_iter = rreq->buffer.iter; + + iov_iter_truncate(&subreq->io_iter, subreq->len); + rolling_buffer_advance(&rreq->buffer, subreq->len); + return subreq->len; +} + +static enum netfs_io_source netfs_cache_prepare_read(struct netfs_io_request *rreq, + struct netfs_io_subrequest *subreq, + loff_t i_size) +{ + struct netfs_cache_resources *cres = &rreq->cache_resources; + enum netfs_io_source source; + + if (!cres->ops) + return NETFS_DOWNLOAD_FROM_SERVER; + source = cres->ops->prepare_read(subreq, i_size); + trace_netfs_sreq(subreq, netfs_sreq_trace_prepare); + return source; + +} + +/* + * Issue a read against the cache. + * - Eats the caller's ref on subreq. + */ +static void netfs_read_cache_to_pagecache(struct netfs_io_request *rreq, + struct netfs_io_subrequest *subreq) +{ + struct netfs_cache_resources *cres = &rreq->cache_resources; + + netfs_stat(&netfs_n_rh_read); + cres->ops->read(cres, subreq->start, &subreq->io_iter, NETFS_READ_HOLE_IGNORE, + netfs_cache_read_terminated, subreq); +} + +static void netfs_queue_read(struct netfs_io_request *rreq, + struct netfs_io_subrequest *subreq, + bool last_subreq) +{ + struct netfs_io_stream *stream = &rreq->io_streams[0]; + + __set_bit(NETFS_SREQ_IN_PROGRESS, &subreq->flags); + + /* We add to the end of the list whilst the collector may be walking + * the list. The collector only goes nextwards and uses the lock to + * remove entries off of the front. + */ + spin_lock(&rreq->lock); + list_add_tail(&subreq->rreq_link, &stream->subrequests); + if (list_is_first(&subreq->rreq_link, &stream->subrequests)) { + stream->front = subreq; + if (!stream->active) { + stream->collected_to = stream->front->start; + /* Store list pointers before active flag */ + smp_store_release(&stream->active, true); + } + } + + if (last_subreq) { + smp_wmb(); /* Write lists before ALL_QUEUED. */ + set_bit(NETFS_RREQ_ALL_QUEUED, &rreq->flags); + } + + spin_unlock(&rreq->lock); +} + +static void netfs_issue_read(struct netfs_io_request *rreq, + struct netfs_io_subrequest *subreq) +{ + switch (subreq->source) { + case NETFS_DOWNLOAD_FROM_SERVER: + rreq->netfs_ops->issue_read(subreq); + break; + case NETFS_READ_FROM_CACHE: + netfs_read_cache_to_pagecache(rreq, subreq); + break; + default: + __set_bit(NETFS_SREQ_CLEAR_TAIL, &subreq->flags); + subreq->error = 0; + iov_iter_zero(subreq->len, &subreq->io_iter); + subreq->transferred = subreq->len; + netfs_read_subreq_terminated(subreq); + break; + } +} + +/* + * Perform a read to the pagecache from a series of sources of different types, + * slicing up the region to be read according to available cache blocks and + * network rsize. + */ +static void netfs_read_to_pagecache(struct netfs_io_request *rreq, + struct readahead_control *ractl) +{ + struct netfs_inode *ictx = netfs_inode(rreq->inode); + unsigned long long start = rreq->start; + ssize_t size = rreq->len; + int ret = 0; + + do { + struct netfs_io_subrequest *subreq; + enum netfs_io_source source = NETFS_SOURCE_UNKNOWN; + ssize_t slice; + + subreq = netfs_alloc_subrequest(rreq); + if (!subreq) { + ret = -ENOMEM; + break; + } + + subreq->start = start; + subreq->len = size; + + source = netfs_cache_prepare_read(rreq, subreq, rreq->i_size); + subreq->source = source; + if (source == NETFS_DOWNLOAD_FROM_SERVER) { + unsigned long long zp = umin(ictx->zero_point, rreq->i_size); + size_t len = subreq->len; + + if (unlikely(rreq->origin == NETFS_READ_SINGLE)) + zp = rreq->i_size; + if (subreq->start >= zp) { + subreq->source = source = NETFS_FILL_WITH_ZEROES; + goto fill_with_zeroes; + } + + if (len > zp - subreq->start) + len = zp - subreq->start; + if (len == 0) { + pr_err("ZERO-LEN READ: R=%08x[%x] l=%zx/%zx s=%llx z=%llx i=%llx", + rreq->debug_id, subreq->debug_index, + subreq->len, size, + subreq->start, ictx->zero_point, rreq->i_size); + break; + } + subreq->len = len; + + netfs_stat(&netfs_n_rh_download); + if (rreq->netfs_ops->prepare_read) { + ret = rreq->netfs_ops->prepare_read(subreq); + if (ret < 0) { + subreq->error = ret; + /* Not queued - release both refs. */ + netfs_put_subrequest(subreq, + netfs_sreq_trace_put_cancel); + netfs_put_subrequest(subreq, + netfs_sreq_trace_put_cancel); + break; + } + trace_netfs_sreq(subreq, netfs_sreq_trace_prepare); + } + goto issue; + } + + fill_with_zeroes: + if (source == NETFS_FILL_WITH_ZEROES) { + subreq->source = NETFS_FILL_WITH_ZEROES; + trace_netfs_sreq(subreq, netfs_sreq_trace_submit); + netfs_stat(&netfs_n_rh_zero); + goto issue; + } + + if (source == NETFS_READ_FROM_CACHE) { + trace_netfs_sreq(subreq, netfs_sreq_trace_submit); + goto issue; + } + + pr_err("Unexpected read source %u\n", source); + WARN_ON_ONCE(1); + break; + + issue: + slice = netfs_prepare_read_iterator(subreq, ractl); + if (slice < 0) { + ret = slice; + subreq->error = ret; + trace_netfs_sreq(subreq, netfs_sreq_trace_cancel); + /* Not queued - release both refs. */ + netfs_put_subrequest(subreq, netfs_sreq_trace_put_cancel); + netfs_put_subrequest(subreq, netfs_sreq_trace_put_cancel); + break; + } + size -= slice; + start += slice; + + netfs_queue_read(rreq, subreq, size <= 0); + netfs_issue_read(rreq, subreq); + cond_resched(); + } while (size > 0); + + if (unlikely(size > 0)) { + smp_wmb(); /* Write lists before ALL_QUEUED. */ + set_bit(NETFS_RREQ_ALL_QUEUED, &rreq->flags); + netfs_wake_collector(rreq); + } + + /* Defer error return as we may need to wait for outstanding I/O. */ + cmpxchg(&rreq->error, 0, ret); +} + +/** + * 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_inode *ictx = netfs_inode(ractl->mapping->host); + unsigned long long start = readahead_pos(ractl); + size_t size = readahead_length(ractl); + int ret; + + rreq = netfs_alloc_request(ractl->mapping, ractl->file, start, size, + NETFS_READAHEAD); + if (IS_ERR(rreq)) + return; + + __set_bit(NETFS_RREQ_OFFLOAD_COLLECTION, &rreq->flags); + + ret = netfs_begin_cache_read(rreq, ictx); + 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); + + rreq->submitted = rreq->start; + if (rolling_buffer_init(&rreq->buffer, rreq->debug_id, ITER_DEST) < 0) + goto cleanup_free; + netfs_read_to_pagecache(rreq, ractl); + + return netfs_put_request(rreq, netfs_rreq_trace_put_return); + +cleanup_free: + return netfs_put_failed_request(rreq); +} +EXPORT_SYMBOL(netfs_readahead); + +/* + * Create a rolling buffer with a single occupying folio. + */ +static int netfs_create_singular_buffer(struct netfs_io_request *rreq, struct folio *folio, + unsigned int rollbuf_flags) +{ + ssize_t added; + + if (rolling_buffer_init(&rreq->buffer, rreq->debug_id, ITER_DEST) < 0) + return -ENOMEM; + + added = rolling_buffer_append(&rreq->buffer, folio, rollbuf_flags); + if (added < 0) + return added; + rreq->submitted = rreq->start + added; + return 0; +} + +/* + * Read into gaps in a folio partially filled by a streaming write. + */ +static int netfs_read_gaps(struct file *file, struct folio *folio) +{ + struct netfs_io_request *rreq; + struct address_space *mapping = folio->mapping; + struct netfs_folio *finfo = netfs_folio_info(folio); + struct netfs_inode *ctx = netfs_inode(mapping->host); + struct folio *sink = NULL; + struct bio_vec *bvec; + unsigned int from = finfo->dirty_offset; + unsigned int to = from + finfo->dirty_len; + unsigned int off = 0, i = 0; + size_t flen = folio_size(folio); + size_t nr_bvec = flen / PAGE_SIZE + 2; + size_t part; + int ret; + + _enter("%lx", folio->index); + + rreq = netfs_alloc_request(mapping, file, folio_pos(folio), flen, NETFS_READ_GAPS); + if (IS_ERR(rreq)) { + ret = PTR_ERR(rreq); + goto alloc_error; + } + + ret = netfs_begin_cache_read(rreq, ctx); + if (ret == -ENOMEM || ret == -EINTR || ret == -ERESTARTSYS) + goto discard; + + netfs_stat(&netfs_n_rh_read_folio); + trace_netfs_read(rreq, rreq->start, rreq->len, netfs_read_trace_read_gaps); + + /* Fiddle the buffer so that a gap at the beginning and/or a gap at the + * end get copied to, but the middle is discarded. + */ + ret = -ENOMEM; + bvec = kmalloc_array(nr_bvec, sizeof(*bvec), GFP_KERNEL); + if (!bvec) + goto discard; + + sink = folio_alloc(GFP_KERNEL, 0); + if (!sink) { + kfree(bvec); + goto discard; + } + + trace_netfs_folio(folio, netfs_folio_trace_read_gaps); + + rreq->direct_bv = bvec; + rreq->direct_bv_count = nr_bvec; + if (from > 0) { + bvec_set_folio(&bvec[i++], folio, from, 0); + off = from; + } + while (off < to) { + part = min_t(size_t, to - off, PAGE_SIZE); + bvec_set_folio(&bvec[i++], sink, part, 0); + off += part; + } + if (to < flen) + bvec_set_folio(&bvec[i++], folio, flen - to, to); + iov_iter_bvec(&rreq->buffer.iter, ITER_DEST, bvec, i, rreq->len); + rreq->submitted = rreq->start + flen; + + netfs_read_to_pagecache(rreq, NULL); + + if (sink) + folio_put(sink); + + ret = netfs_wait_for_read(rreq); + if (ret >= 0) { + flush_dcache_folio(folio); + folio_mark_uptodate(folio); + } + folio_unlock(folio); + netfs_put_request(rreq, netfs_rreq_trace_put_return); + return ret < 0 ? ret : 0; + +discard: + netfs_put_failed_request(rreq); +alloc_error: + folio_unlock(folio); + return ret; +} + +/** + * netfs_read_folio - Helper to manage a read_folio request + * @file: The file to read from + * @folio: The folio to read + * + * Fulfil a read_folio request by drawing data from the cache if + * possible, or the netfs if not. Space beyond the EOF is zero-filled. + * Multiple I/O requests from different sources will get munged together. + * + * The calling netfs must initialise a netfs context contiguous to the vfs + * inode before calling this. + * + * This is usable whether or not caching is enabled. + */ +int netfs_read_folio(struct file *file, struct folio *folio) +{ + struct address_space *mapping = folio->mapping; + struct netfs_io_request *rreq; + struct netfs_inode *ctx = netfs_inode(mapping->host); + int ret; + + if (folio_test_dirty(folio)) { + trace_netfs_folio(folio, netfs_folio_trace_read_gaps); + return netfs_read_gaps(file, folio); + } + + _enter("%lx", folio->index); + + rreq = netfs_alloc_request(mapping, file, + folio_pos(folio), folio_size(folio), + NETFS_READPAGE); + if (IS_ERR(rreq)) { + ret = PTR_ERR(rreq); + goto alloc_error; + } + + ret = netfs_begin_cache_read(rreq, ctx); + if (ret == -ENOMEM || ret == -EINTR || ret == -ERESTARTSYS) + goto discard; + + netfs_stat(&netfs_n_rh_read_folio); + trace_netfs_read(rreq, rreq->start, rreq->len, netfs_read_trace_readpage); + + /* Set up the output buffer */ + ret = netfs_create_singular_buffer(rreq, folio, 0); + if (ret < 0) + goto discard; + + netfs_read_to_pagecache(rreq, NULL); + ret = netfs_wait_for_read(rreq); + netfs_put_request(rreq, netfs_rreq_trace_put_return); + return ret < 0 ? ret : 0; + +discard: + netfs_put_failed_request(rreq); +alloc_error: + folio_unlock(folio); + return ret; +} +EXPORT_SYMBOL(netfs_read_folio); + +/* + * Prepare a folio for writing without reading first + * @folio: The folio being prepared + * @pos: starting position for the write + * @len: length of write + * @always_fill: T if the folio should always be completely filled/cleared + * + * In some cases, write_begin doesn't need to read at all: + * - full folio write + * - write that lies in a folio that is completely beyond EOF + * - write that covers the folio from start to EOF or beyond it + * + * If any of these criteria are met, then zero out the unwritten parts + * of the folio and return true. Otherwise, return false. + */ +static bool netfs_skip_folio_read(struct folio *folio, loff_t pos, size_t len, + bool always_fill) +{ + struct inode *inode = folio_inode(folio); + loff_t i_size = i_size_read(inode); + size_t offset = offset_in_folio(folio, pos); + size_t plen = folio_size(folio); + + if (unlikely(always_fill)) { + if (pos - offset + len <= i_size) + return false; /* Page entirely before EOF */ + folio_zero_segment(folio, 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: + folio_zero_segments(folio, 0, offset, offset + len, plen); + return true; +} + +/** + * netfs_write_begin - Helper to prepare for writing [DEPRECATED] + * @ctx: The netfs context + * @file: The file to read from + * @mapping: The mapping to read from + * @pos: File position at which the write will begin + * @len: The length of the write (may extend beyond the end of the folio chosen) + * @_folio: Where to put the resultant folio + * @_fsdata: Place for the netfs to store a cookie + * + * Pre-read data for a write-begin request by drawing data from the cache if + * possible, or the netfs if not. Space beyond the EOF is zero-filled. + * Multiple I/O requests from different sources will get munged together. + * + * The calling netfs must provide a table of operations, only one of which, + * issue_read, is mandatory. + * + * The check_write_begin() operation can be provided to check for and flush + * conflicting writes once the folio is grabbed and locked. It is passed a + * pointer to the fsdata cookie that gets returned to the VM to be passed to + * write_end. It is permitted to sleep. It should return 0 if the request + * should go ahead or it may return an error. It may also unlock and put the + * folio, provided it sets ``*foliop`` to NULL, in which case a return of 0 + * will cause the folio to be re-got and the process to be retried. + * + * The calling netfs must initialise a netfs context contiguous to the vfs + * inode before calling this. + * + * This is usable whether or not caching is enabled. + * + * Note that this should be considered deprecated and netfs_perform_write() + * used instead. + */ +int netfs_write_begin(struct netfs_inode *ctx, + struct file *file, struct address_space *mapping, + loff_t pos, unsigned int len, struct folio **_folio, + void **_fsdata) +{ + struct netfs_io_request *rreq; + struct folio *folio; + pgoff_t index = pos >> PAGE_SHIFT; + int ret; + +retry: + folio = __filemap_get_folio(mapping, index, FGP_WRITEBEGIN, + mapping_gfp_mask(mapping)); + if (IS_ERR(folio)) + return PTR_ERR(folio); + + if (ctx->ops->check_write_begin) { + /* Allow the netfs (eg. ceph) to flush conflicts. */ + ret = ctx->ops->check_write_begin(file, pos, len, &folio, _fsdata); + if (ret < 0) { + trace_netfs_failure(NULL, NULL, ret, netfs_fail_check_write_begin); + goto error; + } + if (!folio) + goto retry; + } + + if (folio_test_uptodate(folio)) + goto have_folio; + + /* If the folio is beyond the EOF, we want to clear it - unless it's + * within the cache granule containing the EOF, in which case we need + * to preload the granule. + */ + if (!netfs_is_cache_enabled(ctx) && + netfs_skip_folio_read(folio, pos, len, false)) { + netfs_stat(&netfs_n_rh_write_zskip); + goto have_folio_no_wait; + } + + rreq = netfs_alloc_request(mapping, file, + folio_pos(folio), folio_size(folio), + NETFS_READ_FOR_WRITE); + if (IS_ERR(rreq)) { + ret = PTR_ERR(rreq); + goto error; + } + rreq->no_unlock_folio = folio->index; + __set_bit(NETFS_RREQ_NO_UNLOCK_FOLIO, &rreq->flags); + + ret = netfs_begin_cache_read(rreq, ctx); + if (ret == -ENOMEM || ret == -EINTR || ret == -ERESTARTSYS) + goto error_put; + + netfs_stat(&netfs_n_rh_write_begin); + trace_netfs_read(rreq, pos, len, netfs_read_trace_write_begin); + + /* Set up the output buffer */ + ret = netfs_create_singular_buffer(rreq, folio, 0); + if (ret < 0) + goto error_put; + + netfs_read_to_pagecache(rreq, NULL); + ret = netfs_wait_for_read(rreq); + if (ret < 0) + goto error; + netfs_put_request(rreq, netfs_rreq_trace_put_return); + +have_folio: + ret = folio_wait_private_2_killable(folio); + if (ret < 0) + goto error; +have_folio_no_wait: + *_folio = folio; + _leave(" = 0"); + return 0; + +error_put: + netfs_put_failed_request(rreq); +error: + if (folio) { + folio_unlock(folio); + folio_put(folio); + } + _leave(" = %d", ret); + return ret; +} +EXPORT_SYMBOL(netfs_write_begin); + +/* + * Preload the data into a folio we're proposing to write into. + */ +int netfs_prefetch_for_write(struct file *file, struct folio *folio, + size_t offset, size_t len) +{ + struct netfs_io_request *rreq; + struct address_space *mapping = folio->mapping; + struct netfs_inode *ctx = netfs_inode(mapping->host); + unsigned long long start = folio_pos(folio); + size_t flen = folio_size(folio); + int ret; + + _enter("%zx @%llx", flen, start); + + ret = -ENOMEM; + + rreq = netfs_alloc_request(mapping, file, start, flen, + NETFS_READ_FOR_WRITE); + if (IS_ERR(rreq)) { + ret = PTR_ERR(rreq); + goto error; + } + + rreq->no_unlock_folio = folio->index; + __set_bit(NETFS_RREQ_NO_UNLOCK_FOLIO, &rreq->flags); + ret = netfs_begin_cache_read(rreq, ctx); + if (ret == -ENOMEM || ret == -EINTR || ret == -ERESTARTSYS) + goto error_put; + + netfs_stat(&netfs_n_rh_write_begin); + trace_netfs_read(rreq, start, flen, netfs_read_trace_prefetch_for_write); + + /* Set up the output buffer */ + ret = netfs_create_singular_buffer(rreq, folio, NETFS_ROLLBUF_PAGECACHE_MARK); + if (ret < 0) + goto error_put; + + netfs_read_to_pagecache(rreq, NULL); + ret = netfs_wait_for_read(rreq); + netfs_put_request(rreq, netfs_rreq_trace_put_return); + return ret < 0 ? ret : 0; + +error_put: + netfs_put_failed_request(rreq); +error: + _leave(" = %d", ret); + return ret; +} + +/** + * netfs_buffered_read_iter - Filesystem buffered I/O read routine + * @iocb: kernel I/O control block + * @iter: destination for the data read + * + * This is the ->read_iter() routine for all filesystems that can use the page + * cache directly. + * + * The IOCB_NOWAIT flag in iocb->ki_flags indicates that -EAGAIN shall be + * returned when no data can be read without waiting for I/O requests to + * complete; it doesn't prevent readahead. + * + * The IOCB_NOIO flag in iocb->ki_flags indicates that no new I/O requests + * shall be made for the read or for readahead. When no data can be read, + * -EAGAIN shall be returned. When readahead would be triggered, a partial, + * possibly empty read shall be returned. + * + * Return: + * * number of bytes copied, even for partial reads + * * negative error code (or 0 if IOCB_NOIO) if nothing was read + */ +ssize_t netfs_buffered_read_iter(struct kiocb *iocb, struct iov_iter *iter) +{ + struct inode *inode = file_inode(iocb->ki_filp); + struct netfs_inode *ictx = netfs_inode(inode); + ssize_t ret; + + if (WARN_ON_ONCE((iocb->ki_flags & IOCB_DIRECT) || + test_bit(NETFS_ICTX_UNBUFFERED, &ictx->flags))) + return -EINVAL; + + ret = netfs_start_io_read(inode); + if (ret == 0) { + ret = filemap_read(iocb, iter, 0); + netfs_end_io_read(inode); + } + return ret; +} +EXPORT_SYMBOL(netfs_buffered_read_iter); + +/** + * netfs_file_read_iter - Generic filesystem read routine + * @iocb: kernel I/O control block + * @iter: destination for the data read + * + * This is the ->read_iter() routine for all filesystems that can use the page + * cache directly. + * + * The IOCB_NOWAIT flag in iocb->ki_flags indicates that -EAGAIN shall be + * returned when no data can be read without waiting for I/O requests to + * complete; it doesn't prevent readahead. + * + * The IOCB_NOIO flag in iocb->ki_flags indicates that no new I/O requests + * shall be made for the read or for readahead. When no data can be read, + * -EAGAIN shall be returned. When readahead would be triggered, a partial, + * possibly empty read shall be returned. + * + * Return: + * * number of bytes copied, even for partial reads + * * negative error code (or 0 if IOCB_NOIO) if nothing was read + */ +ssize_t netfs_file_read_iter(struct kiocb *iocb, struct iov_iter *iter) +{ + struct netfs_inode *ictx = netfs_inode(iocb->ki_filp->f_mapping->host); + + if ((iocb->ki_flags & IOCB_DIRECT) || + test_bit(NETFS_ICTX_UNBUFFERED, &ictx->flags)) + return netfs_unbuffered_read_iter(iocb, iter); + + return netfs_buffered_read_iter(iocb, iter); +} +EXPORT_SYMBOL(netfs_file_read_iter); |