linux/fs/netfs/io.c
David Howells 3ee1a1fc39 cifs: Cut over to using netfslib
Make the cifs filesystem use netfslib to handle reading and writing on
behalf of cifs.  The changes include:

 (1) Various read_iter/write_iter type functions are turned into wrappers
     around netfslib API functions or are pointed directly at those
     functions:

	cifs_file_direct{,_nobrl}_ops switch to use
	netfs_unbuffered_read_iter and netfs_unbuffered_write_iter.

Large pieces of code that will be removed are #if'd out and will be removed
in subsequent patches.

[?] Why does cifs mark the page dirty in the destination buffer of a DIO
    read?  Should that happen automatically?  Does netfs need to do that?

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Steve French <sfrench@samba.org>
cc: Shyam Prasad N <nspmangalore@gmail.com>
cc: Rohith Surabattula <rohiths.msft@gmail.com>
cc: Jeff Layton <jlayton@kernel.org>
cc: linux-cifs@vger.kernel.org
cc: netfs@lists.linux.dev
cc: linux-fsdevel@vger.kernel.org
cc: linux-mm@kvack.org
2024-05-01 18:08:21 +01:00

648 lines
18 KiB
C

// 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 "internal.h"
/*
* Clear the unread part of an I/O request.
*/
static void netfs_clear_unread(struct netfs_io_subrequest *subreq)
{
iov_iter_zero(iov_iter_count(&subreq->io_iter), &subreq->io_iter);
}
static void netfs_cache_read_terminated(void *priv, ssize_t transferred_or_error,
bool was_async)
{
struct netfs_io_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_io_request *rreq,
struct netfs_io_subrequest *subreq,
enum netfs_read_from_hole read_hole)
{
struct netfs_cache_resources *cres = &rreq->cache_resources;
netfs_stat(&netfs_n_rh_read);
cres->ops->read(cres, subreq->start, &subreq->io_iter, read_hole,
netfs_cache_read_terminated, subreq);
}
/*
* Fill a subrequest region with zeroes.
*/
static void netfs_fill_with_zeroes(struct netfs_io_request *rreq,
struct netfs_io_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_io_request *rreq,
struct netfs_io_subrequest *subreq)
{
netfs_stat(&netfs_n_rh_download);
if (rreq->origin != NETFS_DIO_READ &&
iov_iter_count(&subreq->io_iter) != subreq->len - subreq->transferred)
pr_warn("R=%08x[%u] ITER PRE-MISMATCH %zx != %zx-%zx %lx\n",
rreq->debug_id, subreq->debug_index,
iov_iter_count(&subreq->io_iter), subreq->len,
subreq->transferred, subreq->flags);
rreq->netfs_ops->issue_read(subreq);
}
/*
* Release those waiting.
*/
static void netfs_rreq_completed(struct netfs_io_request *rreq, bool was_async)
{
trace_netfs_rreq(rreq, netfs_rreq_trace_done);
netfs_clear_subrequests(rreq, was_async);
netfs_put_request(rreq, was_async, netfs_rreq_trace_put_complete);
}
/*
* Handle a short read.
*/
static void netfs_rreq_short_read(struct netfs_io_request *rreq,
struct netfs_io_subrequest *subreq)
{
__clear_bit(NETFS_SREQ_SHORT_IO, &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_subrequest(subreq, netfs_sreq_trace_get_short_read);
atomic_inc(&rreq->nr_outstanding);
if (subreq->source == NETFS_READ_FROM_CACHE)
netfs_read_from_cache(rreq, subreq, NETFS_READ_HOLE_CLEAR);
else
netfs_read_from_server(rreq, subreq);
}
/*
* Reset the subrequest iterator prior to resubmission.
*/
static void netfs_reset_subreq_iter(struct netfs_io_request *rreq,
struct netfs_io_subrequest *subreq)
{
size_t remaining = subreq->len - subreq->transferred;
size_t count = iov_iter_count(&subreq->io_iter);
if (count == remaining)
return;
_debug("R=%08x[%u] ITER RESUB-MISMATCH %zx != %zx-%zx-%llx %x\n",
rreq->debug_id, subreq->debug_index,
iov_iter_count(&subreq->io_iter), subreq->transferred,
subreq->len, rreq->i_size,
subreq->io_iter.iter_type);
if (count < remaining)
iov_iter_revert(&subreq->io_iter, remaining - count);
else
iov_iter_advance(&subreq->io_iter, count - remaining);
}
/*
* Resubmit any short or failed operations. Returns true if we got the rreq
* ref back.
*/
static bool netfs_rreq_perform_resubmissions(struct netfs_io_request *rreq)
{
struct netfs_io_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_outstanding);
__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_subrequest(subreq, netfs_sreq_trace_get_resubmit);
atomic_inc(&rreq->nr_outstanding);
netfs_reset_subreq_iter(rreq, subreq);
netfs_read_from_server(rreq, subreq);
} else if (test_bit(NETFS_SREQ_SHORT_IO, &subreq->flags)) {
netfs_rreq_short_read(rreq, subreq);
}
}
/* If we decrement nr_outstanding to 0, the usage ref belongs to us. */
if (atomic_dec_and_test(&rreq->nr_outstanding))
return true;
wake_up_var(&rreq->nr_outstanding);
return false;
}
/*
* Check to see if the data read is still valid.
*/
static void netfs_rreq_is_still_valid(struct netfs_io_request *rreq)
{
struct netfs_io_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);
}
}
}
/*
* Determine how much we can admit to having read from a DIO read.
*/
static void netfs_rreq_assess_dio(struct netfs_io_request *rreq)
{
struct netfs_io_subrequest *subreq;
unsigned int i;
size_t transferred = 0;
for (i = 0; i < rreq->direct_bv_count; i++) {
flush_dcache_page(rreq->direct_bv[i].bv_page);
// TODO: cifs marks pages in the destination buffer
// dirty under some circumstances after a read. Do we
// need to do that too?
set_page_dirty(rreq->direct_bv[i].bv_page);
}
list_for_each_entry(subreq, &rreq->subrequests, rreq_link) {
if (subreq->error || subreq->transferred == 0)
break;
transferred += subreq->transferred;
if (subreq->transferred < subreq->len)
break;
}
for (i = 0; i < rreq->direct_bv_count; i++)
flush_dcache_page(rreq->direct_bv[i].bv_page);
rreq->transferred = transferred;
task_io_account_read(transferred);
if (rreq->iocb) {
rreq->iocb->ki_pos += transferred;
if (rreq->iocb->ki_complete)
rreq->iocb->ki_complete(
rreq->iocb, rreq->error ? rreq->error : transferred);
}
if (rreq->netfs_ops->done)
rreq->netfs_ops->done(rreq);
inode_dio_end(rreq->inode);
}
/*
* 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_io_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;
}
if (rreq->origin != NETFS_DIO_READ)
netfs_rreq_unlock_folios(rreq);
else
netfs_rreq_assess_dio(rreq);
trace_netfs_rreq(rreq, netfs_rreq_trace_wake_ip);
clear_bit_unlock(NETFS_RREQ_IN_PROGRESS, &rreq->flags);
wake_up_bit(&rreq->flags, NETFS_RREQ_IN_PROGRESS);
netfs_rreq_completed(rreq, was_async);
}
static void netfs_rreq_work(struct work_struct *work)
{
struct netfs_io_request *rreq =
container_of(work, struct netfs_io_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_io_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_io_subrequest *subreq,
ssize_t transferred_or_error,
bool was_async)
{
struct netfs_io_request *rreq = subreq->rreq;
int u;
_enter("R=%x[%x]{%llx,%lx},%zd",
rreq->debug_id, 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_COPY_TO_CACHE, &subreq->flags))
set_bit(NETFS_RREQ_COPY_TO_CACHE, &rreq->flags);
out:
trace_netfs_sreq(subreq, netfs_sreq_trace_terminated);
/* If we decrement nr_outstanding to 0, the ref belongs to us. */
u = atomic_dec_return(&rreq->nr_outstanding);
if (u == 0)
netfs_rreq_terminated(rreq, was_async);
else if (u == 1)
wake_up_var(&rreq->nr_outstanding);
netfs_put_subrequest(subreq, was_async, netfs_sreq_trace_put_terminated);
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_IO, &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_io_source netfs_cache_prepare_read(struct netfs_io_subrequest *subreq,
loff_t i_size)
{
struct netfs_io_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_io_source
netfs_rreq_prepare_read(struct netfs_io_request *rreq,
struct netfs_io_subrequest *subreq,
struct iov_iter *io_iter)
{
enum netfs_io_source source = NETFS_DOWNLOAD_FROM_SERVER;
struct netfs_inode *ictx = netfs_inode(rreq->inode);
size_t lsize;
_enter("%llx-%llx,%llx", subreq->start, subreq->start + subreq->len, rreq->i_size);
if (rreq->origin != NETFS_DIO_READ) {
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 (rreq->origin != NETFS_DIO_READ) {
if (subreq->start >= ictx->zero_point) {
source = NETFS_FILL_WITH_ZEROES;
goto set;
}
if (subreq->len > ictx->zero_point - subreq->start)
subreq->len = ictx->zero_point - subreq->start;
}
if (subreq->len > rreq->i_size - subreq->start)
subreq->len = rreq->i_size - subreq->start;
if (rreq->rsize && subreq->len > rreq->rsize)
subreq->len = rreq->rsize;
if (rreq->netfs_ops->clamp_length &&
!rreq->netfs_ops->clamp_length(subreq)) {
source = NETFS_INVALID_READ;
goto out;
}
if (subreq->max_nr_segs) {
lsize = netfs_limit_iter(io_iter, 0, subreq->len,
subreq->max_nr_segs);
if (subreq->len > lsize) {
subreq->len = lsize;
trace_netfs_sreq(subreq, netfs_sreq_trace_limited);
}
}
}
set:
if (subreq->len > rreq->len)
pr_warn("R=%08x[%u] SREQ>RREQ %zx > %llx\n",
rreq->debug_id, subreq->debug_index,
subreq->len, rreq->len);
if (WARN_ON(subreq->len == 0)) {
source = NETFS_INVALID_READ;
goto out;
}
subreq->source = source;
trace_netfs_sreq(subreq, netfs_sreq_trace_prepare);
subreq->io_iter = *io_iter;
iov_iter_truncate(&subreq->io_iter, subreq->len);
iov_iter_advance(io_iter, subreq->len);
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_io_request *rreq,
struct iov_iter *io_iter)
{
struct netfs_io_subrequest *subreq;
enum netfs_io_source source;
subreq = netfs_alloc_subrequest(rreq);
if (!subreq)
return false;
subreq->start = rreq->start + rreq->submitted;
subreq->len = io_iter->count;
_debug("slice %llx,%zx,%llx", 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, io_iter);
if (source == NETFS_INVALID_READ)
goto subreq_failed;
atomic_inc(&rreq->nr_outstanding);
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, NETFS_READ_HOLE_IGNORE);
break;
default:
BUG();
}
return true;
subreq_failed:
rreq->error = subreq->error;
netfs_put_subrequest(subreq, false, netfs_sreq_trace_put_failed);
return false;
}
/*
* Begin the process of reading in a chunk of data, where that data may be
* stitched together from multiple sources, including multiple servers and the
* local cache.
*/
int netfs_begin_read(struct netfs_io_request *rreq, bool sync)
{
struct iov_iter io_iter;
int ret;
_enter("R=%x %llx-%llx",
rreq->debug_id, rreq->start, rreq->start + rreq->len - 1);
if (rreq->len == 0) {
pr_err("Zero-sized read [R=%x]\n", rreq->debug_id);
return -EIO;
}
if (rreq->origin == NETFS_DIO_READ)
inode_dio_begin(rreq->inode);
// TODO: Use bounce buffer if requested
rreq->io_iter = rreq->iter;
INIT_WORK(&rreq->work, netfs_rreq_work);
/* Chop the read into slices according to what the cache and the netfs
* want and submit each one.
*/
netfs_get_request(rreq, netfs_rreq_trace_get_for_outstanding);
atomic_set(&rreq->nr_outstanding, 1);
io_iter = rreq->io_iter;
do {
_debug("submit %llx + %llx >= %llx",
rreq->start, rreq->submitted, rreq->i_size);
if (rreq->origin == NETFS_DIO_READ &&
rreq->start + rreq->submitted >= rreq->i_size)
break;
if (!netfs_rreq_submit_slice(rreq, &io_iter))
break;
if (test_bit(NETFS_RREQ_BLOCKED, &rreq->flags) &&
test_bit(NETFS_RREQ_NONBLOCK, &rreq->flags))
break;
} while (rreq->submitted < rreq->len);
if (!rreq->submitted) {
netfs_put_request(rreq, false, netfs_rreq_trace_put_no_submit);
if (rreq->origin == NETFS_DIO_READ)
inode_dio_end(rreq->inode);
ret = 0;
goto out;
}
if (sync) {
/* Keep nr_outstanding incremented so that the ref always
* belongs to us, and the service code isn't punted off to a
* random thread pool to process. Note that this might start
* further work, such as writing to the cache.
*/
wait_var_event(&rreq->nr_outstanding,
atomic_read(&rreq->nr_outstanding) == 1);
if (atomic_dec_and_test(&rreq->nr_outstanding))
netfs_rreq_assess(rreq, false);
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 &&
rreq->origin != NETFS_DIO_READ) {
trace_netfs_failure(rreq, NULL, ret, netfs_fail_short_read);
ret = -EIO;
}
} else {
/* If we decrement nr_outstanding to 0, the ref belongs to us. */
if (atomic_dec_and_test(&rreq->nr_outstanding))
netfs_rreq_assess(rreq, false);
ret = -EIOCBQUEUED;
}
out:
return ret;
}