blob: 994ec22d40402b7a7c3c5206e434d114ca81298a [file] [log] [blame]
// SPDX-License-Identifier: GPL-2.0-or-later
/* Network filesystem high-level read support.
*
* Copyright (C) 2021 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.com)
*/
#include <linux/module.h>
#include <linux/export.h>
#include <linux/fs.h>
#include <linux/mm.h>
#include <linux/pagemap.h>
#include <linux/slab.h>
#include <linux/uio.h>
#include <linux/sched/mm.h>
#include <linux/task_io_accounting_ops.h>
#include <linux/netfs.h>
#include "internal.h"
#define CREATE_TRACE_POINTS
#include <trace/events/netfs.h>
MODULE_DESCRIPTION("Network fs support");
MODULE_AUTHOR("Red Hat, Inc.");
MODULE_LICENSE("GPL");
unsigned netfs_debug;
module_param_named(debug, netfs_debug, uint, S_IWUSR | S_IRUGO);
MODULE_PARM_DESC(netfs_debug, "Netfs support debugging mask");
static void netfs_rreq_work(struct work_struct *);
static void __netfs_put_subrequest(struct netfs_read_subrequest *, bool);
static void netfs_put_subrequest(struct netfs_read_subrequest *subreq,
bool was_async)
{
if (refcount_dec_and_test(&subreq->usage))
__netfs_put_subrequest(subreq, was_async);
}
static struct netfs_read_request *netfs_alloc_read_request(
const struct netfs_read_request_ops *ops, void *netfs_priv,
struct file *file)
{
static atomic_t debug_ids;
struct netfs_read_request *rreq;
rreq = kzalloc(sizeof(struct netfs_read_request), GFP_KERNEL);
if (rreq) {
rreq->netfs_ops = ops;
rreq->netfs_priv = netfs_priv;
rreq->inode = file_inode(file);
rreq->i_size = i_size_read(rreq->inode);
rreq->debug_id = atomic_inc_return(&debug_ids);
INIT_LIST_HEAD(&rreq->subrequests);
INIT_WORK(&rreq->work, netfs_rreq_work);
refcount_set(&rreq->usage, 1);
__set_bit(NETFS_RREQ_IN_PROGRESS, &rreq->flags);
ops->init_rreq(rreq, file);
netfs_stat(&netfs_n_rh_rreq);
}
return rreq;
}
static void netfs_get_read_request(struct netfs_read_request *rreq)
{
refcount_inc(&rreq->usage);
}
static void netfs_rreq_clear_subreqs(struct netfs_read_request *rreq,
bool was_async)
{
struct netfs_read_subrequest *subreq;
while (!list_empty(&rreq->subrequests)) {
subreq = list_first_entry(&rreq->subrequests,
struct netfs_read_subrequest, rreq_link);
list_del(&subreq->rreq_link);
netfs_put_subrequest(subreq, was_async);
}
}
static void netfs_free_read_request(struct work_struct *work)
{
struct netfs_read_request *rreq =
container_of(work, struct netfs_read_request, work);
netfs_rreq_clear_subreqs(rreq, false);
if (rreq->netfs_priv)
rreq->netfs_ops->cleanup(rreq->mapping, rreq->netfs_priv);
trace_netfs_rreq(rreq, netfs_rreq_trace_free);
if (rreq->cache_resources.ops)
rreq->cache_resources.ops->end_operation(&rreq->cache_resources);
kfree(rreq);
netfs_stat_d(&netfs_n_rh_rreq);
}
static void netfs_put_read_request(struct netfs_read_request *rreq, bool was_async)
{
if (refcount_dec_and_test(&rreq->usage)) {
if (was_async) {
rreq->work.func = netfs_free_read_request;
if (!queue_work(system_unbound_wq, &rreq->work))
BUG();
} else {
netfs_free_read_request(&rreq->work);
}
}
}
/*
* Allocate and partially initialise an I/O request structure.
*/
static struct netfs_read_subrequest *netfs_alloc_subrequest(
struct netfs_read_request *rreq)
{
struct netfs_read_subrequest *subreq;
subreq = kzalloc(sizeof(struct netfs_read_subrequest), GFP_KERNEL);
if (subreq) {
INIT_LIST_HEAD(&subreq->rreq_link);
refcount_set(&subreq->usage, 2);
subreq->rreq = rreq;
netfs_get_read_request(rreq);
netfs_stat(&netfs_n_rh_sreq);
}
return subreq;
}
static void netfs_get_read_subrequest(struct netfs_read_subrequest *subreq)
{
refcount_inc(&subreq->usage);
}
static void __netfs_put_subrequest(struct netfs_read_subrequest *subreq,
bool was_async)
{
struct netfs_read_request *rreq = subreq->rreq;
trace_netfs_sreq(subreq, netfs_sreq_trace_free);
kfree(subreq);
netfs_stat_d(&netfs_n_rh_sreq);
netfs_put_read_request(rreq, was_async);
}
/*
* Clear the unread part of an I/O request.
*/
static void netfs_clear_unread(struct netfs_read_subrequest *subreq)
{
struct iov_iter iter;
iov_iter_xarray(&iter, READ, &subreq->rreq->mapping->i_pages,
subreq->start + subreq->transferred,
subreq->len - subreq->transferred);
iov_iter_zero(iov_iter_count(&iter), &iter);
}
static void netfs_cache_read_terminated(void *priv, ssize_t transferred_or_error,
bool was_async)
{
struct netfs_read_subrequest *subreq = priv;
netfs_subreq_terminated(subreq, transferred_or_error, was_async);
}
/*
* Issue a read against the cache.
* - Eats the caller's ref on subreq.
*/
static void netfs_read_from_cache(struct netfs_read_request *rreq,
struct netfs_read_subrequest *subreq,
bool seek_data)
{
struct netfs_cache_resources *cres = &rreq->cache_resources;
struct iov_iter iter;
netfs_stat(&netfs_n_rh_read);
iov_iter_xarray(&iter, READ, &rreq->mapping->i_pages,
subreq->start + subreq->transferred,
subreq->len - subreq->transferred);
cres->ops->read(cres, subreq->start, &iter, seek_data,
netfs_cache_read_terminated, subreq);
}
/*
* Fill a subrequest region with zeroes.
*/
static void netfs_fill_with_zeroes(struct netfs_read_request *rreq,
struct netfs_read_subrequest *subreq)
{
netfs_stat(&netfs_n_rh_zero);
__set_bit(NETFS_SREQ_CLEAR_TAIL, &subreq->flags);
netfs_subreq_terminated(subreq, 0, false);
}
/*
* Ask the netfs to issue a read request to the server for us.
*
* The netfs is expected to read from subreq->pos + subreq->transferred to
* subreq->pos + subreq->len - 1. It may not backtrack and write data into the
* buffer prior to the transferred point as it might clobber dirty data
* obtained from the cache.
*
* Alternatively, the netfs is allowed to indicate one of two things:
*
* - NETFS_SREQ_SHORT_READ: A short read - it will get called again to try and
* make progress.
*
* - NETFS_SREQ_CLEAR_TAIL: A short read - the rest of the buffer will be
* cleared.
*/
static void netfs_read_from_server(struct netfs_read_request *rreq,
struct netfs_read_subrequest *subreq)
{
netfs_stat(&netfs_n_rh_download);
rreq->netfs_ops->issue_op(subreq);
}
/*
* Release those waiting.
*/
static void netfs_rreq_completed(struct netfs_read_request *rreq, bool was_async)
{
trace_netfs_rreq(rreq, netfs_rreq_trace_done);
netfs_rreq_clear_subreqs(rreq, was_async);
netfs_put_read_request(rreq, was_async);
}
/*
* Deal with the completion of writing the data to the cache. We have to clear
* the PG_fscache bits on the pages involved and release the caller's ref.
*
* May be called in softirq mode and we inherit a ref from the caller.
*/
static void netfs_rreq_unmark_after_write(struct netfs_read_request *rreq,
bool was_async)
{
struct netfs_read_subrequest *subreq;
struct page *page;
pgoff_t unlocked = 0;
bool have_unlocked = false;
rcu_read_lock();
list_for_each_entry(subreq, &rreq->subrequests, rreq_link) {
XA_STATE(xas, &rreq->mapping->i_pages, subreq->start / PAGE_SIZE);
xas_for_each(&xas, page, (subreq->start + subreq->len - 1) / PAGE_SIZE) {
/* We might have multiple writes from the same huge
* page, but we mustn't unlock a page more than once.
*/
if (have_unlocked && page->index <= unlocked)
continue;
unlocked = page->index;
end_page_fscache(page);
have_unlocked = true;
}
}
rcu_read_unlock();
netfs_rreq_completed(rreq, was_async);
}
static void netfs_rreq_copy_terminated(void *priv, ssize_t transferred_or_error,
bool was_async)
{
struct netfs_read_subrequest *subreq = priv;
struct netfs_read_request *rreq = subreq->rreq;
if (IS_ERR_VALUE(transferred_or_error)) {
netfs_stat(&netfs_n_rh_write_failed);
trace_netfs_failure(rreq, subreq, transferred_or_error,
netfs_fail_copy_to_cache);
} else {
netfs_stat(&netfs_n_rh_write_done);
}
trace_netfs_sreq(subreq, netfs_sreq_trace_write_term);
/* If we decrement nr_wr_ops to 0, the ref belongs to us. */
if (atomic_dec_and_test(&rreq->nr_wr_ops))
netfs_rreq_unmark_after_write(rreq, was_async);
netfs_put_subrequest(subreq, was_async);
}
/*
* Perform any outstanding writes to the cache. We inherit a ref from the
* caller.
*/
static void netfs_rreq_do_write_to_cache(struct netfs_read_request *rreq)
{
struct netfs_cache_resources *cres = &rreq->cache_resources;
struct netfs_read_subrequest *subreq, *next, *p;
struct iov_iter iter;
int ret;
trace_netfs_rreq(rreq, netfs_rreq_trace_write);
/* We don't want terminating writes trying to wake us up whilst we're
* still going through the list.
*/
atomic_inc(&rreq->nr_wr_ops);
list_for_each_entry_safe(subreq, p, &rreq->subrequests, rreq_link) {
if (!test_bit(NETFS_SREQ_WRITE_TO_CACHE, &subreq->flags)) {
list_del_init(&subreq->rreq_link);
netfs_put_subrequest(subreq, false);
}
}
list_for_each_entry(subreq, &rreq->subrequests, rreq_link) {
/* Amalgamate adjacent writes */
while (!list_is_last(&subreq->rreq_link, &rreq->subrequests)) {
next = list_next_entry(subreq, rreq_link);
if (next->start != subreq->start + subreq->len)
break;
subreq->len += next->len;
list_del_init(&next->rreq_link);
netfs_put_subrequest(next, false);
}
ret = cres->ops->prepare_write(cres, &subreq->start, &subreq->len,
rreq->i_size);
if (ret < 0) {
trace_netfs_failure(rreq, subreq, ret, netfs_fail_prepare_write);
trace_netfs_sreq(subreq, netfs_sreq_trace_write_skip);
continue;
}
iov_iter_xarray(&iter, WRITE, &rreq->mapping->i_pages,
subreq->start, subreq->len);
atomic_inc(&rreq->nr_wr_ops);
netfs_stat(&netfs_n_rh_write);
netfs_get_read_subrequest(subreq);
trace_netfs_sreq(subreq, netfs_sreq_trace_write);
cres->ops->write(cres, subreq->start, &iter,
netfs_rreq_copy_terminated, subreq);
}
/* If we decrement nr_wr_ops to 0, the usage ref belongs to us. */
if (atomic_dec_and_test(&rreq->nr_wr_ops))
netfs_rreq_unmark_after_write(rreq, false);
}
static void netfs_rreq_write_to_cache_work(struct work_struct *work)
{
struct netfs_read_request *rreq =
container_of(work, struct netfs_read_request, work);
netfs_rreq_do_write_to_cache(rreq);
}
static void netfs_rreq_write_to_cache(struct netfs_read_request *rreq,
bool was_async)
{
if (was_async) {
rreq->work.func = netfs_rreq_write_to_cache_work;
if (!queue_work(system_unbound_wq, &rreq->work))
BUG();
} else {
netfs_rreq_do_write_to_cache(rreq);
}
}
/*
* Unlock the pages in a read operation. We need to set PG_fscache on any
* pages we're going to write back before we unlock them.
*/
static void netfs_rreq_unlock(struct netfs_read_request *rreq)
{
struct netfs_read_subrequest *subreq;
struct page *page;
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;
int i;
XA_STATE(xas, &rreq->mapping->i_pages, start_page);
if (test_bit(NETFS_RREQ_FAILED, &rreq->flags)) {
__clear_bit(NETFS_RREQ_WRITE_TO_CACHE, &rreq->flags);
list_for_each_entry(subreq, &rreq->subrequests, rreq_link) {
__clear_bit(NETFS_SREQ_WRITE_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_read_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, page, last_page) {
unsigned int pgpos = (page->index - start_page) * PAGE_SIZE;
unsigned int pgend = pgpos + thp_size(page);
bool pg_failed = false;
for (;;) {
if (!subreq) {
pg_failed = true;
break;
}
if (test_bit(NETFS_SREQ_WRITE_TO_CACHE, &subreq->flags))
set_page_fscache(page);
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) {
for (i = 0; i < thp_nr_pages(page); i++)
flush_dcache_page(page);
SetPageUptodate(page);
}
if (!test_bit(NETFS_RREQ_DONT_UNLOCK_PAGES, &rreq->flags)) {
if (page->index == rreq->no_unlock_page &&
test_bit(NETFS_RREQ_NO_UNLOCK_PAGE, &rreq->flags))
_debug("no unlock");
else
unlock_page(page);
}
}
rcu_read_unlock();
task_io_account_read(account);
if (rreq->netfs_ops->done)
rreq->netfs_ops->done(rreq);
}
/*
* Handle a short read.
*/
static void netfs_rreq_short_read(struct netfs_read_request *rreq,
struct netfs_read_subrequest *subreq)
{
__clear_bit(NETFS_SREQ_SHORT_READ, &subreq->flags);
__set_bit(NETFS_SREQ_SEEK_DATA_READ, &subreq->flags);
netfs_stat(&netfs_n_rh_short_read);
trace_netfs_sreq(subreq, netfs_sreq_trace_resubmit_short);
netfs_get_read_subrequest(subreq);
atomic_inc(&rreq->nr_rd_ops);
if (subreq->source == NETFS_READ_FROM_CACHE)
netfs_read_from_cache(rreq, subreq, true);
else
netfs_read_from_server(rreq, subreq);
}
/*
* Resubmit any short or failed operations. Returns true if we got the rreq
* ref back.
*/
static bool netfs_rreq_perform_resubmissions(struct netfs_read_request *rreq)
{
struct netfs_read_subrequest *subreq;
WARN_ON(in_interrupt());
trace_netfs_rreq(rreq, netfs_rreq_trace_resubmit);
/* We don't want terminating submissions trying to wake us up whilst
* we're still going through the list.
*/
atomic_inc(&rreq->nr_rd_ops);
__clear_bit(NETFS_RREQ_INCOMPLETE_IO, &rreq->flags);
list_for_each_entry(subreq, &rreq->subrequests, rreq_link) {
if (subreq->error) {
if (subreq->source != NETFS_READ_FROM_CACHE)
break;
subreq->source = NETFS_DOWNLOAD_FROM_SERVER;
subreq->error = 0;
netfs_stat(&netfs_n_rh_download_instead);
trace_netfs_sreq(subreq, netfs_sreq_trace_download_instead);
netfs_get_read_subrequest(subreq);
atomic_inc(&rreq->nr_rd_ops);
netfs_read_from_server(rreq, subreq);
} else if (test_bit(NETFS_SREQ_SHORT_READ, &subreq->flags)) {
netfs_rreq_short_read(rreq, subreq);
}
}
/* If we decrement nr_rd_ops to 0, the usage ref belongs to us. */
if (atomic_dec_and_test(&rreq->nr_rd_ops))
return true;
wake_up_var(&rreq->nr_rd_ops);
return false;
}
/*
* Check to see if the data read is still valid.
*/
static void netfs_rreq_is_still_valid(struct netfs_read_request *rreq)
{
struct netfs_read_subrequest *subreq;
if (!rreq->netfs_ops->is_still_valid ||
rreq->netfs_ops->is_still_valid(rreq))
return;
list_for_each_entry(subreq, &rreq->subrequests, rreq_link) {
if (subreq->source == NETFS_READ_FROM_CACHE) {
subreq->error = -ESTALE;
__set_bit(NETFS_RREQ_INCOMPLETE_IO, &rreq->flags);
}
}
}
/*
* Assess the state of a read request and decide what to do next.
*
* Note that we could be in an ordinary kernel thread, on a workqueue or in
* softirq context at this point. We inherit a ref from the caller.
*/
static void netfs_rreq_assess(struct netfs_read_request *rreq, bool was_async)
{
trace_netfs_rreq(rreq, netfs_rreq_trace_assess);
again:
netfs_rreq_is_still_valid(rreq);
if (!test_bit(NETFS_RREQ_FAILED, &rreq->flags) &&
test_bit(NETFS_RREQ_INCOMPLETE_IO, &rreq->flags)) {
if (netfs_rreq_perform_resubmissions(rreq))
goto again;
return;
}
netfs_rreq_unlock(rreq);
clear_bit_unlock(NETFS_RREQ_IN_PROGRESS, &rreq->flags);
wake_up_bit(&rreq->flags, NETFS_RREQ_IN_PROGRESS);
if (test_bit(NETFS_RREQ_WRITE_TO_CACHE, &rreq->flags))
return netfs_rreq_write_to_cache(rreq, was_async);
netfs_rreq_completed(rreq, was_async);
}
static void netfs_rreq_work(struct work_struct *work)
{
struct netfs_read_request *rreq =
container_of(work, struct netfs_read_request, work);
netfs_rreq_assess(rreq, false);
}
/*
* Handle the completion of all outstanding I/O operations on a read request.
* We inherit a ref from the caller.
*/
static void netfs_rreq_terminated(struct netfs_read_request *rreq,
bool was_async)
{
if (test_bit(NETFS_RREQ_INCOMPLETE_IO, &rreq->flags) &&
was_async) {
if (!queue_work(system_unbound_wq, &rreq->work))
BUG();
} else {
netfs_rreq_assess(rreq, was_async);
}
}
/**
* netfs_subreq_terminated - Note the termination of an I/O operation.
* @subreq: The I/O request that has terminated.
* @transferred_or_error: The amount of data transferred or an error code.
* @was_async: The termination was asynchronous
*
* This tells the read helper that a contributory I/O operation has terminated,
* one way or another, and that it should integrate the results.
*
* The caller indicates in @transferred_or_error the outcome of the operation,
* supplying a positive value to indicate the number of bytes transferred, 0 to
* indicate a failure to transfer anything that should be retried or a negative
* error code. The helper will look after reissuing I/O operations as
* appropriate and writing downloaded data to the cache.
*
* If @was_async is true, the caller might be running in softirq or interrupt
* context and we can't sleep.
*/
void netfs_subreq_terminated(struct netfs_read_subrequest *subreq,
ssize_t transferred_or_error,
bool was_async)
{
struct netfs_read_request *rreq = subreq->rreq;
int u;
_enter("[%u]{%llx,%lx},%zd",
subreq->debug_index, subreq->start, subreq->flags,
transferred_or_error);
switch (subreq->source) {
case NETFS_READ_FROM_CACHE:
netfs_stat(&netfs_n_rh_read_done);
break;
case NETFS_DOWNLOAD_FROM_SERVER:
netfs_stat(&netfs_n_rh_download_done);
break;
default:
break;
}
if (IS_ERR_VALUE(transferred_or_error)) {
subreq->error = transferred_or_error;
trace_netfs_failure(rreq, subreq, transferred_or_error,
netfs_fail_read);
goto failed;
}
if (WARN(transferred_or_error > subreq->len - subreq->transferred,
"Subreq overread: R%x[%x] %zd > %zu - %zu",
rreq->debug_id, subreq->debug_index,
transferred_or_error, subreq->len, subreq->transferred))
transferred_or_error = subreq->len - subreq->transferred;
subreq->error = 0;
subreq->transferred += transferred_or_error;
if (subreq->transferred < subreq->len)
goto incomplete;
complete:
__clear_bit(NETFS_SREQ_NO_PROGRESS, &subreq->flags);
if (test_bit(NETFS_SREQ_WRITE_TO_CACHE, &subreq->flags))
set_bit(NETFS_RREQ_WRITE_TO_CACHE, &rreq->flags);
out:
trace_netfs_sreq(subreq, netfs_sreq_trace_terminated);
/* If we decrement nr_rd_ops to 0, the ref belongs to us. */
u = atomic_dec_return(&rreq->nr_rd_ops);
if (u == 0)
netfs_rreq_terminated(rreq, was_async);
else if (u == 1)
wake_up_var(&rreq->nr_rd_ops);
netfs_put_subrequest(subreq, was_async);
return;
incomplete:
if (test_bit(NETFS_SREQ_CLEAR_TAIL, &subreq->flags)) {
netfs_clear_unread(subreq);
subreq->transferred = subreq->len;
goto complete;
}
if (transferred_or_error == 0) {
if (__test_and_set_bit(NETFS_SREQ_NO_PROGRESS, &subreq->flags)) {
subreq->error = -ENODATA;
goto failed;
}
} else {
__clear_bit(NETFS_SREQ_NO_PROGRESS, &subreq->flags);
}
__set_bit(NETFS_SREQ_SHORT_READ, &subreq->flags);
set_bit(NETFS_RREQ_INCOMPLETE_IO, &rreq->flags);
goto out;
failed:
if (subreq->source == NETFS_READ_FROM_CACHE) {
netfs_stat(&netfs_n_rh_read_failed);
set_bit(NETFS_RREQ_INCOMPLETE_IO, &rreq->flags);
} else {
netfs_stat(&netfs_n_rh_download_failed);
set_bit(NETFS_RREQ_FAILED, &rreq->flags);
rreq->error = subreq->error;
}
goto out;
}
EXPORT_SYMBOL(netfs_subreq_terminated);
static enum netfs_read_source netfs_cache_prepare_read(struct netfs_read_subrequest *subreq,
loff_t i_size)
{
struct netfs_read_request *rreq = subreq->rreq;
struct netfs_cache_resources *cres = &rreq->cache_resources;
if (cres->ops)
return cres->ops->prepare_read(subreq, i_size);
if (subreq->start >= rreq->i_size)
return NETFS_FILL_WITH_ZEROES;
return NETFS_DOWNLOAD_FROM_SERVER;
}
/*
* Work out what sort of subrequest the next one will be.
*/
static enum netfs_read_source
netfs_rreq_prepare_read(struct netfs_read_request *rreq,
struct netfs_read_subrequest *subreq)
{
enum netfs_read_source source;
_enter("%llx-%llx,%llx", subreq->start, subreq->start + subreq->len, rreq->i_size);
source = netfs_cache_prepare_read(subreq, rreq->i_size);
if (source == NETFS_INVALID_READ)
goto out;
if (source == NETFS_DOWNLOAD_FROM_SERVER) {
/* Call out to the netfs to let it shrink the request to fit
* its own I/O sizes and boundaries. If it shinks it here, it
* will be called again to make simultaneous calls; if it wants
* to make serial calls, it can indicate a short read and then
* we will call it again.
*/
if (subreq->len > rreq->i_size - subreq->start)
subreq->len = rreq->i_size - subreq->start;
if (rreq->netfs_ops->clamp_length &&
!rreq->netfs_ops->clamp_length(subreq)) {
source = NETFS_INVALID_READ;
goto out;
}
}
if (WARN_ON(subreq->len == 0))
source = NETFS_INVALID_READ;
out:
subreq->source = source;
trace_netfs_sreq(subreq, netfs_sreq_trace_prepare);
return source;
}
/*
* Slice off a piece of a read request and submit an I/O request for it.
*/
static bool netfs_rreq_submit_slice(struct netfs_read_request *rreq,
unsigned int *_debug_index)
{
struct netfs_read_subrequest *subreq;
enum netfs_read_source source;
subreq = netfs_alloc_subrequest(rreq);
if (!subreq)
return false;
subreq->debug_index = (*_debug_index)++;
subreq->start = rreq->start + rreq->submitted;
subreq->len = rreq->len - rreq->submitted;
_debug("slice %llx,%zx,%zx", subreq->start, subreq->len, rreq->submitted);
list_add_tail(&subreq->rreq_link, &rreq->subrequests);
/* Call out to the cache to find out what it can do with the remaining
* subset. It tells us in subreq->flags what it decided should be done
* and adjusts subreq->len down if the subset crosses a cache boundary.
*
* Then when we hand the subset, it can choose to take a subset of that
* (the starts must coincide), in which case, we go around the loop
* again and ask it to download the next piece.
*/
source = netfs_rreq_prepare_read(rreq, subreq);
if (source == NETFS_INVALID_READ)
goto subreq_failed;
atomic_inc(&rreq->nr_rd_ops);
rreq->submitted += subreq->len;
trace_netfs_sreq(subreq, netfs_sreq_trace_submit);
switch (source) {
case NETFS_FILL_WITH_ZEROES:
netfs_fill_with_zeroes(rreq, subreq);
break;
case NETFS_DOWNLOAD_FROM_SERVER:
netfs_read_from_server(rreq, subreq);
break;
case NETFS_READ_FROM_CACHE:
netfs_read_from_cache(rreq, subreq, false);
break;
default:
BUG();
}
return true;
subreq_failed:
rreq->error = subreq->error;
netfs_put_subrequest(subreq, false);
return false;
}
static void netfs_cache_expand_readahead(struct netfs_read_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_read_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
* @ops: The network filesystem's operations for the helper to use
* @netfs_priv: Private netfs data to be retained in the 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 provide a table of operations, only one of which,
* issue_op, is mandatory. It may also be passed a private token, which will
* be retained in rreq->netfs_priv and will be cleaned up by ops->cleanup().
*
* This is usable whether or not caching is enabled.
*/
void netfs_readahead(struct readahead_control *ractl,
const struct netfs_read_request_ops *ops,
void *netfs_priv)
{
struct netfs_read_request *rreq;
struct page *page;
unsigned int debug_index = 0;
int ret;
_enter("%lx,%x", readahead_index(ractl), readahead_count(ractl));
if (readahead_count(ractl) == 0)
goto cleanup;
rreq = netfs_alloc_read_request(ops, netfs_priv, ractl->file);
if (!rreq)
goto cleanup;
rreq->mapping = ractl->mapping;
rreq->start = readahead_pos(ractl);
rreq->len = readahead_length(ractl);
if (ops->begin_cache_operation) {
ret = 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);
atomic_set(&rreq->nr_rd_ops, 1);
do {
if (!netfs_rreq_submit_slice(rreq, &debug_index))
break;
} while (rreq->submitted < rreq->len);
/* Drop the refs on the pages here rather than in the cache or
* filesystem. The locks will be dropped in netfs_rreq_unlock().
*/
while ((page = readahead_page(ractl)))
put_page(page);
/* If we decrement nr_rd_ops to 0, the ref belongs to us. */
if (atomic_dec_and_test(&rreq->nr_rd_ops))
netfs_rreq_assess(rreq, false);
return;
cleanup_free:
netfs_put_read_request(rreq, false);
return;
cleanup:
if (netfs_priv)
ops->cleanup(ractl->mapping, netfs_priv);
return;
}
EXPORT_SYMBOL(netfs_readahead);
/**
* netfs_readpage - Helper to manage a readpage request
* @file: The file to read from
* @page: The page to read
* @ops: The network filesystem's operations for the helper to use
* @netfs_priv: Private netfs data to be retained in the request
*
* 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 provide a table of operations, only one of which,
* issue_op, is mandatory. It may also be passed a private token, which will
* be retained in rreq->netfs_priv and will be cleaned up by ops->cleanup().
*
* This is usable whether or not caching is enabled.
*/
int netfs_readpage(struct file *file,
struct page *page,
const struct netfs_read_request_ops *ops,
void *netfs_priv)
{
struct netfs_read_request *rreq;
unsigned int debug_index = 0;
int ret;
_enter("%lx", page_index(page));
rreq = netfs_alloc_read_request(ops, netfs_priv, file);
if (!rreq) {
if (netfs_priv)
ops->cleanup(netfs_priv, page_file_mapping(page));
unlock_page(page);
return -ENOMEM;
}
rreq->mapping = page_file_mapping(page);
rreq->start = page_file_offset(page);
rreq->len = thp_size(page);
if (ops->begin_cache_operation) {
ret = ops->begin_cache_operation(rreq);
if (ret == -ENOMEM || ret == -EINTR || ret == -ERESTARTSYS) {
unlock_page(page);
goto out;
}
}
netfs_stat(&netfs_n_rh_readpage);
trace_netfs_read(rreq, rreq->start, rreq->len, netfs_read_trace_readpage);
netfs_get_read_request(rreq);
atomic_set(&rreq->nr_rd_ops, 1);
do {
if (!netfs_rreq_submit_slice(rreq, &debug_index))
break;
} while (rreq->submitted < rreq->len);
/* Keep nr_rd_ops incremented so that the ref always belongs to us, and
* the service code isn't punted off to a random thread pool to
* process.
*/
do {
wait_var_event(&rreq->nr_rd_ops, atomic_read(&rreq->nr_rd_ops) == 1);
netfs_rreq_assess(rreq, false);
} while (test_bit(NETFS_RREQ_IN_PROGRESS, &rreq->flags));
ret = rreq->error;
if (ret == 0 && rreq->submitted < rreq->len) {
trace_netfs_failure(rreq, NULL, ret, netfs_fail_short_readpage);
ret = -EIO;
}
out:
netfs_put_read_request(rreq, false);
return ret;
}
EXPORT_SYMBOL(netfs_readpage);
/**
* netfs_skip_page_read - prep a page for writing without reading first
* @page: page being prepared
* @pos: starting position for the write
* @len: length of write
*
* In some cases, write_begin doesn't need to read at all:
* - full page write
* - write that lies in a page that is completely beyond EOF
* - write that covers the the page from start to EOF or beyond it
*
* If any of these criteria are met, then zero out the unwritten parts
* of the page and return true. Otherwise, return false.
*/
static bool netfs_skip_page_read(struct page *page, loff_t pos, size_t len)
{
struct inode *inode = page->mapping->host;
loff_t i_size = i_size_read(inode);
size_t offset = offset_in_thp(page, pos);
/* Full page write */
if (offset == 0 && len >= thp_size(page))
return true;
/* pos beyond last page in the file */
if (pos - offset >= i_size)
goto zero_out;
/* Write that covers from the start of the page to EOF or beyond */
if (offset == 0 && (pos + len) >= i_size)
goto zero_out;
return false;
zero_out:
zero_user_segments(page, 0, offset, offset + len, thp_size(page));
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 page chosen)
* @flags: AOP_* flags
* @_page: Where to put the resultant page
* @_fsdata: Place for the netfs to store a cookie
* @ops: The network filesystem's operations for the helper to use
* @netfs_priv: Private netfs data to be retained in the request
*
* 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 page 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 page and return -EAGAIN to cause the page to be
* regot; or return an error.
*
* 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 flags,
struct page **_page, void **_fsdata,
const struct netfs_read_request_ops *ops,
void *netfs_priv)
{
struct netfs_read_request *rreq;
struct page *page, *xpage;
struct inode *inode = file_inode(file);
unsigned int debug_index = 0;
pgoff_t index = pos >> PAGE_SHIFT;
int ret;
DEFINE_READAHEAD(ractl, file, NULL, mapping, index);
retry:
page = grab_cache_page_write_begin(mapping, index, flags);
if (!page)
return -ENOMEM;
if (ops->check_write_begin) {
/* Allow the netfs (eg. ceph) to flush conflicts. */
ret = ops->check_write_begin(file, pos, len, page, _fsdata);
if (ret < 0) {
trace_netfs_failure(NULL, NULL, ret, netfs_fail_check_write_begin);
if (ret == -EAGAIN)
goto retry;
goto error;
}
}
if (PageUptodate(page))
goto have_page;
/* 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 (!ops->is_cache_enabled(inode) &&
netfs_skip_page_read(page, pos, len)) {
netfs_stat(&netfs_n_rh_write_zskip);
goto have_page_no_wait;
}
ret = -ENOMEM;
rreq = netfs_alloc_read_request(ops, netfs_priv, file);
if (!rreq)
goto error;
rreq->mapping = page->mapping;
rreq->start = page_offset(page);
rreq->len = thp_size(page);
rreq->no_unlock_page = page->index;
__set_bit(NETFS_RREQ_NO_UNLOCK_PAGE, &rreq->flags);
netfs_priv = NULL;
if (ops->begin_cache_operation) {
ret = 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 = thp_nr_pages(page);
netfs_rreq_expand(rreq, &ractl);
netfs_get_read_request(rreq);
/* We hold the page locks, so we can drop the references */
while ((xpage = readahead_page(&ractl)))
if (xpage != page)
put_page(xpage);
atomic_set(&rreq->nr_rd_ops, 1);
do {
if (!netfs_rreq_submit_slice(rreq, &debug_index))
break;
} while (rreq->submitted < rreq->len);
/* Keep nr_rd_ops incremented so that the ref always belongs to us, and
* the service code isn't punted off to a random thread pool to
* process.
*/
for (;;) {
wait_var_event(&rreq->nr_rd_ops, atomic_read(&rreq->nr_rd_ops) == 1);
netfs_rreq_assess(rreq, false);
if (!test_bit(NETFS_RREQ_IN_PROGRESS, &rreq->flags))
break;
cond_resched();
}
ret = rreq->error;
if (ret == 0 && rreq->submitted < rreq->len) {
trace_netfs_failure(rreq, NULL, ret, netfs_fail_short_write_begin);
ret = -EIO;
}
netfs_put_read_request(rreq, false);
if (ret < 0)
goto error;
have_page:
ret = wait_on_page_fscache_killable(page);
if (ret < 0)
goto error;
have_page_no_wait:
if (netfs_priv)
ops->cleanup(netfs_priv, mapping);
*_page = page;
_leave(" = 0");
return 0;
error_put:
netfs_put_read_request(rreq, false);
error:
unlock_page(page);
put_page(page);
if (netfs_priv)
ops->cleanup(netfs_priv, mapping);
_leave(" = %d", ret);
return ret;
}
EXPORT_SYMBOL(netfs_write_begin);