// 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 ([email protected])
*/
#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));
}
/*
* Decant the list of folios to read into a rolling buffer.
*/
static size_t netfs_load_buffer_from_ra(struct netfs_io_request *rreq,
struct folio_queue *folioq)
{
unsigned int order, nr;
size_t size = 0;
nr = __readahead_batch(rreq->ractl, (struct page **)folioq->vec.folios,
ARRAY_SIZE(folioq->vec.folios));
folioq->vec.nr = nr;
for (int i = 0; i < nr; i++) {
struct folio *folio = folioq_folio(folioq, i);
trace_netfs_folio(folio, netfs_folio_trace_read);
order = folio_order(folio);
folioq->orders[i] = order;
size += PAGE_SIZE << order;
}
for (int i = nr; i < folioq_nr_slots(folioq); i++)
folioq_clear(folioq, i);
return size;
}
/*
* 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 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 (rreq->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.
*/
while (rreq->submitted < subreq->start + rsize) {
struct folio_queue *tail = rreq->buffer_tail, *new;
size_t added;
new = kmalloc(sizeof(*new), GFP_NOFS);
if (!new)
return -ENOMEM;
netfs_stat(&netfs_n_folioq);
folioq_init(new);
new->prev = tail;
tail->next = new;
rreq->buffer_tail = new;
added = netfs_load_buffer_from_ra(rreq, new);
rreq->iter.count += added;
rreq->submitted += added;
}
}
subreq->len = rsize;
if (unlikely(rreq->io_streams[0].sreq_max_segs)) {
size_t limit = netfs_limit_iter(&rreq->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->iter;
if (iov_iter_is_folioq(&subreq->io_iter)) {
if (subreq->io_iter.folioq_slot >= folioq_nr_slots(subreq->io_iter.folioq)) {
subreq->io_iter.folioq = subreq->io_iter.folioq->next;
subreq->io_iter.folioq_slot = 0;
}
subreq->curr_folioq = (struct folio_queue *)subreq->io_iter.folioq;
subreq->curr_folioq_slot = subreq->io_iter.folioq_slot;
subreq->curr_folio_order = subreq->curr_folioq->orders[subreq->curr_folioq_slot];
}
iov_iter_truncate(&subreq->io_iter, subreq->len);
iov_iter_advance(&rreq->iter, 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;
if (!cres->ops)
return NETFS_DOWNLOAD_FROM_SERVER;
return cres->ops->prepare_read(subreq, i_size);
}
static void netfs_cache_read_terminated(void *priv, ssize_t transferred_or_error,
bool was_async)
{
struct netfs_io_subrequest *subreq = priv;
if (transferred_or_error < 0) {
netfs_read_subreq_terminated(subreq, transferred_or_error, was_async);
return;
}
if (transferred_or_error > 0)
subreq->transferred += transferred_or_error;
netfs_read_subreq_terminated(subreq, 0, was_async);
}
/*
* 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);
}
/*
* 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 netfs_inode *ictx = netfs_inode(rreq->inode);
unsigned long long start = rreq->start;
ssize_t size = rreq->len;
int ret = 0;
atomic_inc(&rreq->nr_outstanding);
do {
struct netfs_io_subrequest *subreq;
enum netfs_io_source source = NETFS_DOWNLOAD_FROM_SERVER;
ssize_t slice;
subreq = netfs_alloc_subrequest(rreq);
if (!subreq) {
ret = -ENOMEM;
break;
}
subreq->start = start;
subreq->len = size;
atomic_inc(&rreq->nr_outstanding);
spin_lock_bh(&rreq->lock);
list_add_tail(&subreq->rreq_link, &rreq->subrequests);
subreq->prev_donated = rreq->prev_donated;
rreq->prev_donated = 0;
trace_netfs_sreq(subreq, netfs_sreq_trace_added);
spin_unlock_bh(&rreq->lock);
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 (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) {
atomic_dec(&rreq->nr_outstanding);
netfs_put_subrequest(subreq, false,
netfs_sreq_trace_put_cancel);
break;
}
trace_netfs_sreq(subreq, netfs_sreq_trace_prepare);
}
slice = netfs_prepare_read_iterator(subreq);
if (slice < 0) {
atomic_dec(&rreq->nr_outstanding);
netfs_put_subrequest(subreq, false, netfs_sreq_trace_put_cancel);
ret = slice;
break;
}
rreq->netfs_ops->issue_read(subreq);
goto done;
}
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);
slice = netfs_prepare_read_iterator(subreq);
__set_bit(NETFS_SREQ_CLEAR_TAIL, &subreq->flags);
netfs_read_subreq_terminated(subreq, 0, false);
goto done;
}
if (source == NETFS_READ_FROM_CACHE) {
trace_netfs_sreq(subreq, netfs_sreq_trace_submit);
slice = netfs_prepare_read_iterator(subreq);
netfs_read_cache_to_pagecache(rreq, subreq);
goto done;
}
pr_err("Unexpected read source %u\n", source);
WARN_ON_ONCE(1);
break;
done:
size -= slice;
start += slice;
cond_resched();
} while (size > 0);
if (atomic_dec_and_test(&rreq->nr_outstanding))
netfs_rreq_terminated(rreq, false);
/* Defer error return as we may need to wait for outstanding I/O. */
cmpxchg(&rreq->error, 0, ret);
}
/*
* Wait for the read operation to complete, successfully or otherwise.
*/
static int netfs_wait_for_read(struct netfs_io_request *rreq)
{
int ret;
trace_netfs_rreq(rreq, netfs_rreq_trace_wait_ip);
wait_on_bit(&rreq->flags, NETFS_RREQ_IN_PROGRESS, TASK_UNINTERRUPTIBLE);
ret = rreq->error;
if (ret == 0 && rreq->submitted < rreq->len) {
trace_netfs_failure(rreq, NULL, ret, netfs_fail_short_read);
ret = -EIO;
}
return ret;
}
/*
* Set up the initial folioq of buffer folios in the rolling buffer and set the
* iterator to refer to it.
*/
static int netfs_prime_buffer(struct netfs_io_request *rreq)
{
struct folio_queue *folioq;
size_t added;
folioq = kmalloc(sizeof(*folioq), GFP_KERNEL);
if (!folioq)
return -ENOMEM;
netfs_stat(&netfs_n_folioq);
folioq_init(folioq);
rreq->buffer = folioq;
rreq->buffer_tail = folioq;
rreq->submitted = rreq->start;
iov_iter_folio_queue(&rreq->iter, ITER_DEST, folioq, 0, 0, 0);
added = netfs_load_buffer_from_ra(rreq, folioq);
rreq->iter.count += added;
rreq->submitted += added;
return 0;
}
/*
* Drop the ref on each folio that we inherited from the VM readahead code. We
* still have the folio locks to pin the page until we complete the I/O.
*
* Note that we can't just release the batch in each queue struct as we use the
* occupancy count in other places.
*/
static void netfs_put_ra_refs(struct folio_queue *folioq)
{
struct folio_batch fbatch;
folio_batch_init(&fbatch);
while (folioq) {
for (unsigned int slot = 0; slot < folioq_count(folioq); slot++) {
struct folio *folio = folioq_folio(folioq, slot);
if (!folio)
continue;
trace_netfs_folio(folio, netfs_folio_trace_read_put);
if (!folio_batch_add(&fbatch, folio))
folio_batch_release(&fbatch);
}
folioq = folioq->next;
}
folio_batch_release(&fbatch);
}
/**
* 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;
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->ractl = ractl;
if (netfs_prime_buffer(rreq) < 0)
goto cleanup_free;
netfs_read_to_pagecache(rreq);
/* Release the folio refs whilst we're waiting for the I/O. */
netfs_put_ra_refs(rreq->buffer);
netfs_put_request(rreq, true, netfs_rreq_trace_put_return);
return;
cleanup_free:
netfs_put_request(rreq, false, netfs_rreq_trace_put_failed);
return;
}
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)
{
struct folio_queue *folioq;
folioq = kmalloc(sizeof(*folioq), GFP_KERNEL);
if (!folioq)
return -ENOMEM;
netfs_stat(&netfs_n_folioq);
folioq_init(folioq);
folioq_append(folioq, folio);
BUG_ON(folioq_folio(folioq, 0) != folio);
BUG_ON(folioq_folio_order(folioq, 0) != folio_order(folio));
rreq->buffer = folioq;
rreq->buffer_tail = folioq;
rreq->submitted = rreq->start + rreq->len;
iov_iter_folio_queue(&rreq->iter, ITER_DEST, folioq, 0, 0, rreq->len);
rreq->ractl = (struct readahead_control *)1UL;
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->iter, ITER_DEST, bvec, i, rreq->len);
rreq->submitted = rreq->start + flen;
netfs_read_to_pagecache(rreq);
if (sink)
folio_put(sink);
ret = netfs_wait_for_read(rreq);
if (ret == 0) {
flush_dcache_folio(folio);
folio_mark_uptodate(folio);
}
folio_unlock(folio);
netfs_put_request(rreq, false, netfs_rreq_trace_put_return);
return ret < 0 ? ret : 0;
discard:
netfs_put_request(rreq, false, netfs_rreq_trace_put_discard);
alloc_error:
folio_unlock(folio);
return ret;
}
/**
* netfs_read_folio - Helper to manage a read_folio request
* @file: The file to read from
* @folio: The folio to read
*
* Fulfil a read_folio request by drawing data from the cache if
* possible, or the netfs if not. Space beyond the EOF is zero-filled.
* Multiple I/O requests from different sources will get munged together.
*
* The calling netfs must initialise a netfs context contiguous to the vfs
* inode before calling this.
*
* This is usable whether or not caching is enabled.
*/
int netfs_read_folio(struct file *file, struct folio *folio)
{
struct address_space *mapping = folio->mapping;
struct netfs_io_request *rreq;
struct netfs_inode *ctx = netfs_inode(mapping->host);
int ret;
if (folio_test_dirty(folio)) {
trace_netfs_folio(folio, netfs_folio_trace_read_gaps);
return netfs_read_gaps(file, folio);
}
_enter("%lx", folio->index);
rreq = netfs_alloc_request(mapping, file,
folio_pos(folio), folio_size(folio),
NETFS_READPAGE);
if (IS_ERR(rreq)) {
ret = PTR_ERR(rreq);
goto alloc_error;
}
ret = netfs_begin_cache_read(rreq, ctx);
if (ret == -ENOMEM || ret == -EINTR || ret == -ERESTARTSYS)
goto discard;
netfs_stat(&netfs_n_rh_read_folio);
trace_netfs_read(rreq, rreq->start, rreq->len, netfs_read_trace_readpage);
/* Set up the output buffer */
ret = netfs_create_singular_buffer(rreq, folio);
if (ret < 0)
goto discard;
netfs_read_to_pagecache(rreq);
ret = netfs_wait_for_read(rreq);
netfs_put_request(rreq, false, netfs_rreq_trace_put_return);
return ret < 0 ? ret : 0;
discard:
netfs_put_request(rreq, false, netfs_rreq_trace_put_discard);
alloc_error:
folio_unlock(folio);
return ret;
}
EXPORT_SYMBOL(netfs_read_folio);
/*
* Prepare a folio for writing without reading first
* @folio: The folio being prepared
* @pos: starting position for the write
* @len: length of write
* @always_fill: T if the folio should always be completely filled/cleared
*
* In some cases, write_begin doesn't need to read at all:
* - full folio write
* - write that lies in a folio that is completely beyond EOF
* - write that covers the folio from start to EOF or beyond it
*
* If any of these criteria are met, then zero out the unwritten parts
* of the folio and return true. Otherwise, return false.
*/
static bool netfs_skip_folio_read(struct folio *folio, loff_t pos, size_t len,
bool always_fill)
{
struct inode *inode = folio_inode(folio);
loff_t i_size = i_size_read(inode);
size_t offset = offset_in_folio(folio, pos);
size_t plen = folio_size(folio);
if (unlikely(always_fill)) {
if (pos - offset + len <= i_size)
return false; /* Page entirely before EOF */
zero_user_segment(&folio->page, 0, plen);
folio_mark_uptodate(folio);
return true;
}
/* Full folio write */
if (offset == 0 && len >= plen)
return true;
/* Page entirely beyond the end of the file */
if (pos - offset >= i_size)
goto zero_out;
/* Write that covers from the start of the folio to EOF or beyond */
if (offset == 0 && (pos + len) >= i_size)
goto zero_out;
return false;
zero_out:
zero_user_segments(&folio->page, 0, offset, offset + len, plen);
return true;
}
/**
* netfs_write_begin - Helper to prepare for writing [DEPRECATED]
* @ctx: The netfs context
* @file: The file to read from
* @mapping: The mapping to read from
* @pos: File position at which the write will begin
* @len: The length of the write (may extend beyond the end of the folio chosen)
* @_folio: Where to put the resultant folio
* @_fsdata: Place for the netfs to store a cookie
*
* Pre-read data for a write-begin request by drawing data from the cache if
* possible, or the netfs if not. Space beyond the EOF is zero-filled.
* Multiple I/O requests from different sources will get munged together.
*
* The calling netfs must provide a table of operations, only one of which,
* issue_read, is mandatory.
*
* The check_write_begin() operation can be provided to check for and flush
* conflicting writes once the folio is grabbed and locked. It is passed a
* pointer to the fsdata cookie that gets returned to the VM to be passed to
* write_end. It is permitted to sleep. It should return 0 if the request
* should go ahead or it may return an error. It may also unlock and put the
* folio, provided it sets ``*foliop`` to NULL, in which case a return of 0
* will cause the folio to be re-got and the process to be retried.
*
* The calling netfs must initialise a netfs context contiguous to the vfs
* inode before calling this.
*
* This is usable whether or not caching is enabled.
*
* Note that this should be considered deprecated and netfs_perform_write()
* used instead.
*/
int netfs_write_begin(struct netfs_inode *ctx,
struct file *file, struct address_space *mapping,
loff_t pos, unsigned int len, struct folio **_folio,
void **_fsdata)
{
struct netfs_io_request *rreq;
struct folio *folio;
pgoff_t index = pos >> PAGE_SHIFT;
int ret;
retry:
folio = __filemap_get_folio(mapping, index, FGP_WRITEBEGIN,
mapping_gfp_mask(mapping));
if (IS_ERR(folio))
return PTR_ERR(folio);
if (ctx->ops->check_write_begin) {
/* Allow the netfs (eg. ceph) to flush conflicts. */
ret = ctx->ops->check_write_begin(file, pos, len, &folio, _fsdata);
if (ret < 0) {
trace_netfs_failure(NULL, NULL, ret, netfs_fail_check_write_begin);
goto error;
}
if (!folio)
goto retry;
}
if (folio_test_uptodate(folio))
goto have_folio;
/* If the page is beyond the EOF, we want to clear it - unless it's
* within the cache granule containing the EOF, in which case we need
* to preload the granule.
*/
if (!netfs_is_cache_enabled(ctx) &&
netfs_skip_folio_read(folio, pos, len, false)) {
netfs_stat(&netfs_n_rh_write_zskip);
goto have_folio_no_wait;
}
rreq = netfs_alloc_request(mapping, file,
folio_pos(folio), folio_size(folio),
NETFS_READ_FOR_WRITE);
if (IS_ERR(rreq)) {
ret = PTR_ERR(rreq);
goto error;
}
rreq->no_unlock_folio = folio->index;
__set_bit(NETFS_RREQ_NO_UNLOCK_FOLIO, &rreq->flags);
ret = netfs_begin_cache_read(rreq, ctx);
if (ret == -ENOMEM || ret == -EINTR || ret == -ERESTARTSYS)
goto error_put;
netfs_stat(&netfs_n_rh_write_begin);
trace_netfs_read(rreq, pos, len, netfs_read_trace_write_begin);
/* Set up the output buffer */
ret = netfs_create_singular_buffer(rreq, folio);
if (ret < 0)
goto error_put;
netfs_read_to_pagecache(rreq);
ret = netfs_wait_for_read(rreq);
if (ret < 0)
goto error;
netfs_put_request(rreq, false, netfs_rreq_trace_put_return);
have_folio:
ret = folio_wait_private_2_killable(folio);
if (ret < 0)
goto error;
have_folio_no_wait:
*_folio = folio;
_leave(" = 0");
return 0;
error_put:
netfs_put_request(rreq, false, netfs_rreq_trace_put_failed);
error:
if (folio) {
folio_unlock(folio);
folio_put(folio);
}
_leave(" = %d", ret);
return ret;
}
EXPORT_SYMBOL(netfs_write_begin);
/*
* Preload the data into a page we're proposing to write into.
*/
int netfs_prefetch_for_write(struct file *file, struct folio *folio,
size_t offset, size_t len)
{
struct netfs_io_request *rreq;
struct address_space *mapping = folio->mapping;
struct netfs_inode *ctx = netfs_inode(mapping->host);
unsigned long long start = folio_pos(folio);
size_t flen = folio_size(folio);
int ret;
_enter("%zx @%llx", flen, start);
ret = -ENOMEM;
rreq = netfs_alloc_request(mapping, file, start, flen,
NETFS_READ_FOR_WRITE);
if (IS_ERR(rreq)) {
ret = PTR_ERR(rreq);
goto error;
}
rreq->no_unlock_folio = folio->index;
__set_bit(NETFS_RREQ_NO_UNLOCK_FOLIO, &rreq->flags);
ret = netfs_begin_cache_read(rreq, ctx);
if (ret == -ENOMEM || ret == -EINTR || ret == -ERESTARTSYS)
goto error_put;
netfs_stat(&netfs_n_rh_write_begin);
trace_netfs_read(rreq, start, flen, netfs_read_trace_prefetch_for_write);
/* Set up the output buffer */
ret = netfs_create_singular_buffer(rreq, folio);
if (ret < 0)
goto error_put;
folioq_mark2(rreq->buffer, 0);
netfs_read_to_pagecache(rreq);
ret = netfs_wait_for_read(rreq);
netfs_put_request(rreq, false, netfs_rreq_trace_put_return);
return ret;
error_put:
netfs_put_request(rreq, false, netfs_rreq_trace_put_discard);
error:
_leave(" = %d", ret);
return ret;
}
/**
* netfs_buffered_read_iter - Filesystem buffered I/O read routine
* @iocb: kernel I/O control block
* @iter: destination for the data read
*
* This is the ->read_iter() routine for all filesystems that can use the page
* cache directly.
*
* The IOCB_NOWAIT flag in iocb->ki_flags indicates that -EAGAIN shall be
* returned when no data can be read without waiting for I/O requests to
* complete; it doesn't prevent readahead.
*
* The IOCB_NOIO flag in iocb->ki_flags indicates that no new I/O requests
* shall be made for the read or for readahead. When no data can be read,
* -EAGAIN shall be returned. When readahead would be triggered, a partial,
* possibly empty read shall be returned.
*
* Return:
* * number of bytes copied, even for partial reads
* * negative error code (or 0 if IOCB_NOIO) if nothing was read
*/
ssize_t netfs_buffered_read_iter(struct kiocb *iocb, struct iov_iter *iter)
{
struct inode *inode = file_inode(iocb->ki_filp);
struct netfs_inode *ictx = netfs_inode(inode);
ssize_t ret;
if (WARN_ON_ONCE((iocb->ki_flags & IOCB_DIRECT) ||
test_bit(NETFS_ICTX_UNBUFFERED, &ictx->flags)))
return -EINVAL;
ret = netfs_start_io_read(inode);
if (ret == 0) {
ret = filemap_read(iocb, iter, 0);
netfs_end_io_read(inode);
}
return ret;
}
EXPORT_SYMBOL(netfs_buffered_read_iter);
/**
* netfs_file_read_iter - Generic filesystem read routine
* @iocb: kernel I/O control block
* @iter: destination for the data read
*
* This is the ->read_iter() routine for all filesystems that can use the page
* cache directly.
*
* The IOCB_NOWAIT flag in iocb->ki_flags indicates that -EAGAIN shall be
* returned when no data can be read without waiting for I/O requests to
* complete; it doesn't prevent readahead.
*
* The IOCB_NOIO flag in iocb->ki_flags indicates that no new I/O requests
* shall be made for the read or for readahead. When no data can be read,
* -EAGAIN shall be returned. When readahead would be triggered, a partial,
* possibly empty read shall be returned.
*
* Return:
* * number of bytes copied, even for partial reads
* * negative error code (or 0 if IOCB_NOIO) if nothing was read
*/
ssize_t netfs_file_read_iter(struct kiocb *iocb, struct iov_iter *iter)
{
struct netfs_inode *ictx = netfs_inode(iocb->ki_filp->f_mapping->host);
if ((iocb->ki_flags & IOCB_DIRECT) ||
test_bit(NETFS_ICTX_UNBUFFERED, &ictx->flags))
return netfs_unbuffered_read_iter(iocb, iter);
return netfs_buffered_read_iter(iocb, iter);
}
EXPORT_SYMBOL(netfs_file_read_iter);
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