[PATCH v4 21/33] netfs: Add support for caching single monolithic objects such as AFS dirs

David Howells
2024-11-08T17:35:26Z

Add support for caching the content of a file that contains a single
monolithic object that must be read/written with a single I/O operation,
such as an AFS directory.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Jeff Layton <jlayton@kernel.org>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: netfs@lists.linux.dev
cc: linux-afs@lists.infradead.org
cc: linux-fsdevel@vger.kernel.org
---
fs/netfs/Makefile | 1 +
fs/netfs/buffered_read.c | 11 +-
fs/netfs/internal.h | 2 +
fs/netfs/main.c | 2 +
fs/netfs/objects.c | 2 +
fs/netfs/read_collect.c | 45 +++++++-
fs/netfs/read_single.c | 202 ++++++++++++++++++++++++++++++++++
fs/netfs/stats.c | 4 +-
fs/netfs/write_collect.c | 6 +-
fs/netfs/write_issue.c | 203 ++++++++++++++++++++++++++++++++++-
include/linux/netfs.h | 10 ++
include/trace/events/netfs.h | 4 +
12 files changed, 478 insertions(+), 14 deletions(-)
create mode 100644 fs/netfs/read_single.c

diff --git a/fs/netfs/Makefile b/fs/netfs/Makefile
index cbb30bdeacc4..b43188d64bd8 100644
--- a/fs/netfs/Makefile
+++ b/fs/netfs/Makefile
@@ -13,6 +13,7 @@ netfs-y := \
read_collect.o \
read_pgpriv2.o \
read_retry.o \
+ read_single.o \
rolling_buffer.o \
write_collect.o \
write_issue.o \
diff --git a/fs/netfs/buffered_read.c b/fs/netfs/buffered_read.c
index 4a48b79b8807..61287f6f6706 100644
--- a/fs/netfs/buffered_read.c
+++ b/fs/netfs/buffered_read.c
@@ -137,14 +137,17 @@ static enum netfs_io_source netfs_cache_prepare_read(struct netfs_io_request *rr
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;
- return cres->ops->prepare_read(subreq, i_size);
+ source = cres->ops->prepare_read(subreq, i_size);
+ trace_netfs_sreq(subreq, netfs_sreq_trace_prepare);
+ return source;
+
}

-static void netfs_cache_read_terminated(void *priv, ssize_t transferred_or_error,
- bool was_async)
+void netfs_cache_read_terminated(void *priv, ssize_t transferred_or_error, bool was_async)
{
struct netfs_io_subrequest *subreq = priv;

@@ -213,6 +216,8 @@ static void netfs_read_to_pagecache(struct netfs_io_request *rreq)
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;
diff --git a/fs/netfs/internal.h b/fs/netfs/internal.h
index ba32ca61063c..e236f752af88 100644
--- a/fs/netfs/internal.h
+++ b/fs/netfs/internal.h
@@ -23,6 +23,7 @@
/*
* buffered_read.c
*/
+void netfs_cache_read_terminated(void *priv, ssize_t transferred_or_error, bool was_async);
int netfs_prefetch_for_write(struct file *file, struct folio *folio,
size_t offset, size_t len);

@@ -110,6 +111,7 @@ void netfs_unlock_abandoned_read_pages(struct netfs_io_request *rreq);
extern atomic_t netfs_n_rh_dio_read;
extern atomic_t netfs_n_rh_readahead;
extern atomic_t netfs_n_rh_read_folio;
+extern atomic_t netfs_n_rh_read_single;
extern atomic_t netfs_n_rh_rreq;
extern atomic_t netfs_n_rh_sreq;
extern atomic_t netfs_n_rh_download;
diff --git a/fs/netfs/main.c b/fs/netfs/main.c
index 6c7be1377ee0..8c1922c0cb42 100644
--- a/fs/netfs/main.c
+++ b/fs/netfs/main.c
@@ -37,9 +37,11 @@ static const char *netfs_origins[nr__netfs_io_origin] = {
[NETFS_READAHEAD] = "RA",
[NETFS_READPAGE] = "RP",
[NETFS_READ_GAPS] = "RG",
+ [NETFS_READ_SINGLE] = "R1",
[NETFS_READ_FOR_WRITE] = "RW",
[NETFS_DIO_READ] = "DR",
[NETFS_WRITEBACK] = "WB",
+ [NETFS_WRITEBACK_SINGLE] = "W1",
[NETFS_WRITETHROUGH] = "WT",
[NETFS_UNBUFFERED_WRITE] = "UW",
[NETFS_DIO_WRITE] = "DW",
diff --git a/fs/netfs/objects.c b/fs/netfs/objects.c
index 8c98b70eb3a4..dde4a679d9e2 100644
--- a/fs/netfs/objects.c
+++ b/fs/netfs/objects.c
@@ -54,6 +54,7 @@ struct netfs_io_request *netfs_alloc_request(struct address_space *mapping,
if (origin == NETFS_READAHEAD ||
origin == NETFS_READPAGE ||
origin == NETFS_READ_GAPS ||
+ origin == NETFS_READ_SINGLE ||
origin == NETFS_READ_FOR_WRITE ||
origin == NETFS_DIO_READ)
INIT_WORK(&rreq->work, NULL);
@@ -196,6 +197,7 @@ struct netfs_io_subrequest *netfs_alloc_subrequest(struct netfs_io_request *rreq
case NETFS_READAHEAD:
case NETFS_READPAGE:
case NETFS_READ_GAPS:
+ case NETFS_READ_SINGLE:
case NETFS_READ_FOR_WRITE:
case NETFS_DIO_READ:
INIT_WORK(&subreq->work, netfs_read_subreq_termination_worker);
diff --git a/fs/netfs/read_collect.c b/fs/netfs/read_collect.c
index 53ef7e0f3e9c..9124c8c36f9d 100644
--- a/fs/netfs/read_collect.c
+++ b/fs/netfs/read_collect.c
@@ -358,6 +358,39 @@ static void netfs_rreq_assess_dio(struct netfs_io_request *rreq)
inode_dio_end(rreq->inode);
}

+/*
+ * Do processing after reading a monolithic single object.
+ */
+static void netfs_rreq_assess_single(struct netfs_io_request *rreq)
+{
+ struct netfs_io_subrequest *subreq;
+ struct netfs_io_stream *stream = &rreq->io_streams[0];
+
+ subreq = list_first_entry_or_null(&stream->subrequests,
+ struct netfs_io_subrequest, rreq_link);
+ if (subreq) {
+ if (test_bit(NETFS_SREQ_FAILED, &subreq->flags))
+ rreq->error = subreq->error;
+ else
+ rreq->transferred = subreq->transferred;
+
+ if (!rreq->error && subreq->source == NETFS_DOWNLOAD_FROM_SERVER &&
+ fscache_resources_valid(&rreq->cache_resources)) {
+ trace_netfs_rreq(rreq, netfs_rreq_trace_dirty);
+ netfs_single_mark_inode_dirty(rreq->inode);
+ }
+ }
+
+ if (rreq->iocb) {
+ rreq->iocb->ki_pos += rreq->transferred;
+ if (rreq->iocb->ki_complete)
+ rreq->iocb->ki_complete(
+ rreq->iocb, rreq->error ? rreq->error : rreq->transferred);
+ }
+ if (rreq->netfs_ops->done)
+ rreq->netfs_ops->done(rreq);
+}
+
/*
* Assess the state of a read request and decide what to do next.
*
@@ -375,9 +408,17 @@ void netfs_rreq_terminated(struct netfs_io_request *rreq)
return;
}

- if (rreq->origin == NETFS_DIO_READ ||
- rreq->origin == NETFS_READ_GAPS)
+ switch (rreq->origin) {
+ case NETFS_DIO_READ:
+ case NETFS_READ_GAPS:
netfs_rreq_assess_dio(rreq);
+ break;
+ case NETFS_READ_SINGLE:
+ netfs_rreq_assess_single(rreq);
+ break;
+ default:
+ break;
+ }
task_io_account_read(rreq->transferred);

trace_netfs_rreq(rreq, netfs_rreq_trace_wake_ip);
diff --git a/fs/netfs/read_single.c b/fs/netfs/read_single.c
new file mode 100644
index 000000000000..2a66c5fde071
--- /dev/null
+++ b/fs/netfs/read_single.c
@@ -0,0 +1,202 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* Single, monolithic object support (e.g. AFS directory).
+ *
+ * Copyright (C) 2024 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ */
+
+#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"
+
+/**
+ * netfs_single_mark_inode_dirty - Mark a single, monolithic object inode dirty
+ * @inode: The inode to mark
+ *
+ * Mark an inode that contains a single, monolithic object as dirty so that its
+ * writepages op will get called. If set, the SINGLE_NO_UPLOAD flag indicates
+ * that the object will only be written to the cache and not uploaded (e.g. AFS
+ * directory contents).
+ */
+void netfs_single_mark_inode_dirty(struct inode *inode)
+{
+ struct netfs_inode *ictx = netfs_inode(inode);
+ bool cache_only = test_bit(NETFS_ICTX_SINGLE_NO_UPLOAD, &ictx->flags);
+ bool caching = fscache_cookie_enabled(netfs_i_cookie(netfs_inode(inode)));
+
+ if (cache_only && !caching)
+ return;
+
+ mark_inode_dirty(inode);
+
+ if (caching && !(inode->i_state & I_PINNING_NETFS_WB)) {
+ bool need_use = false;
+
+ spin_lock(&inode->i_lock);
+ if (!(inode->i_state & I_PINNING_NETFS_WB)) {
+ inode->i_state |= I_PINNING_NETFS_WB;
+ need_use = true;
+ }
+ spin_unlock(&inode->i_lock);
+
+ if (need_use)
+ fscache_use_cookie(netfs_i_cookie(ictx), true);
+ }
+
+}
+EXPORT_SYMBOL(netfs_single_mark_inode_dirty);
+
+static int netfs_single_begin_cache_read(struct netfs_io_request *rreq, struct netfs_inode *ctx)
+{
+ return fscache_begin_read_operation(&rreq->cache_resources, netfs_i_cookie(ctx));
+}
+
+static void netfs_single_cache_prepare_read(struct netfs_io_request *rreq,
+ struct netfs_io_subrequest *subreq)
+{
+ struct netfs_cache_resources *cres = &rreq->cache_resources;
+
+ if (!cres->ops) {
+ subreq->source = NETFS_DOWNLOAD_FROM_SERVER;
+ return;
+ }
+ subreq->source = cres->ops->prepare_read(subreq, rreq->i_size);
+ trace_netfs_sreq(subreq, netfs_sreq_trace_prepare);
+
+}
+
+static void netfs_single_read_cache(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_FAIL,
+ netfs_cache_read_terminated, subreq);
+}
+
+/*
+ * Perform a read to a buffer from the cache or the server. Only a single
+ * subreq is permitted as the object must be fetched in a single transaction.
+ */
+static int netfs_single_dispatch_read(struct netfs_io_request *rreq)
+{
+ struct netfs_io_subrequest *subreq;
+ int ret = 0;
+
+ atomic_set(&rreq->nr_outstanding, 1);
+
+ subreq = netfs_alloc_subrequest(rreq);
+ if (!subreq) {
+ ret = -ENOMEM;
+ goto out;
+ }
+
+ subreq->source = NETFS_DOWNLOAD_FROM_SERVER;
+ subreq->start = 0;
+ subreq->len = rreq->len;
+ subreq->io_iter = rreq->buffer.iter;
+
+ atomic_inc(&rreq->nr_outstanding);
+
+ spin_lock_bh(&rreq->lock);
+ list_add_tail(&subreq->rreq_link, &rreq->subrequests);
+ trace_netfs_sreq(subreq, netfs_sreq_trace_added);
+ spin_unlock_bh(&rreq->lock);
+
+ netfs_single_cache_prepare_read(rreq, subreq);
+ switch (subreq->source) {
+ case NETFS_DOWNLOAD_FROM_SERVER:
+ netfs_stat(&netfs_n_rh_download);
+ if (rreq->netfs_ops->prepare_read) {
+ ret = rreq->netfs_ops->prepare_read(subreq);
+ if (ret < 0)
+ goto cancel;
+ }
+
+ rreq->netfs_ops->issue_read(subreq);
+ rreq->submitted += subreq->len;
+ break;
+ case NETFS_READ_FROM_CACHE:
+ trace_netfs_sreq(subreq, netfs_sreq_trace_submit);
+ netfs_single_read_cache(rreq, subreq);
+ rreq->submitted += subreq->len;
+ ret = 0;
+ break;
+ default:
+ pr_warn("Unexpected single-read source %u\n", subreq->source);
+ WARN_ON_ONCE(true);
+ ret = -EIO;
+ break;
+ }
+
+out:
+ if (atomic_dec_and_test(&rreq->nr_outstanding))
+ netfs_rreq_terminated(rreq);
+ return ret;
+cancel:
+ atomic_dec(&rreq->nr_outstanding);
+ netfs_put_subrequest(subreq, false, netfs_sreq_trace_put_cancel);
+ goto out;
+}
+
+/**
+ * netfs_read_single - Synchronously read a single blob of pages.
+ * @inode: The inode to read from.
+ * @file: The file we're using to read or NULL.
+ * @iter: The buffer we're reading into.
+ *
+ * Fulfil a read request for a single monolithic object by drawing data from
+ * the cache if possible, or the netfs if not. The buffer may be larger than
+ * the file content; unused beyond the EOF will be zero-filled. The content
+ * will be read with a single I/O request (though this may 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. If caching is enabled,
+ * the data will be stored as a single object into the cache.
+ */
+ssize_t netfs_read_single(struct inode *inode, struct file *file, struct iov_iter *iter)
+{
+ struct netfs_io_request *rreq;
+ struct netfs_inode *ictx = netfs_inode(inode);
+ ssize_t ret;
+
+ rreq = netfs_alloc_request(inode->i_mapping, file, 0, iov_iter_count(iter),
+ NETFS_READ_SINGLE);
+ if (IS_ERR(rreq))
+ return PTR_ERR(rreq);
+
+ ret = netfs_single_begin_cache_read(rreq, ictx);
+ if (ret == -ENOMEM || ret == -EINTR || ret == -ERESTARTSYS)
+ goto cleanup_free;
+
+ netfs_stat(&netfs_n_rh_read_single);
+ trace_netfs_read(rreq, 0, rreq->len, netfs_read_trace_read_single);
+
+ rreq->buffer.iter = *iter;
+ netfs_single_dispatch_read(rreq);
+
+ 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)
+ ret = rreq->transferred;
+ netfs_put_request(rreq, true, netfs_rreq_trace_put_return);
+ return ret;
+
+cleanup_free:
+ netfs_put_request(rreq, false, netfs_rreq_trace_put_failed);
+ return ret;
+}
+EXPORT_SYMBOL(netfs_read_single);
diff --git a/fs/netfs/stats.c b/fs/netfs/stats.c
index 8e63516b40f6..f1af344266cc 100644
--- a/fs/netfs/stats.c
+++ b/fs/netfs/stats.c
@@ -12,6 +12,7 @@
atomic_t netfs_n_rh_dio_read;
atomic_t netfs_n_rh_readahead;
atomic_t netfs_n_rh_read_folio;
+atomic_t netfs_n_rh_read_single;
atomic_t netfs_n_rh_rreq;
atomic_t netfs_n_rh_sreq;
atomic_t netfs_n_rh_download;
@@ -46,10 +47,11 @@ atomic_t netfs_n_folioq;

int netfs_stats_show(struct seq_file *m, void *v)
{
- seq_printf(m, "Reads : DR=%u RA=%u RF=%u WB=%u WBZ=%u\n",
+ seq_printf(m, "Reads : DR=%u RA=%u RF=%u RS=%u WB=%u WBZ=%u\n",
atomic_read(&netfs_n_rh_dio_read),
atomic_read(&netfs_n_rh_readahead),
atomic_read(&netfs_n_rh_read_folio),
+ atomic_read(&netfs_n_rh_read_single),
atomic_read(&netfs_n_rh_write_begin),
atomic_read(&netfs_n_rh_write_zskip));
seq_printf(m, "Writes : BW=%u WT=%u DW=%u WP=%u 2C=%u\n",
diff --git a/fs/netfs/write_collect.c b/fs/netfs/write_collect.c
index d291b31dd074..3d8b87c8e6a6 100644
--- a/fs/netfs/write_collect.c
+++ b/fs/netfs/write_collect.c
@@ -17,7 +17,7 @@
#define HIT_PENDING 0x01 /* A front op was still pending */
#define NEED_REASSESS 0x02 /* Need to loop round and reassess */
#define MADE_PROGRESS 0x04 /* Made progress cleaning up a stream or the folio set */
-#define BUFFERED 0x08 /* The pagecache needs cleaning up */
+#define NEED_UNLOCK 0x08 /* The pagecache needs unlocking */
#define NEED_RETRY 0x10 /* A front op requests retrying */
#define SAW_FAILURE 0x20 /* One stream or hit a permanent failure */

@@ -179,7 +179,7 @@ static void netfs_collect_write_results(struct netfs_io_request *wreq)
if (wreq->origin == NETFS_WRITEBACK ||
wreq->origin == NETFS_WRITETHROUGH ||
wreq->origin == NETFS_PGPRIV2_COPY_TO_CACHE)
- notes = BUFFERED;
+ notes = NEED_UNLOCK;
else
notes = 0;

@@ -276,7 +276,7 @@ static void netfs_collect_write_results(struct netfs_io_request *wreq)
trace_netfs_collect_state(wreq, wreq->collected_to, notes);

/* Unlock any folios that we have now finished with. */
- if (notes & BUFFERED) {
+ if (notes & NEED_UNLOCK) {
if (wreq->cleaned_to < wreq->collected_to)
netfs_writeback_unlock_folios(wreq, &notes);
} else {
diff --git a/fs/netfs/write_issue.c b/fs/netfs/write_issue.c
index 10b5300b9448..cd2b349243b3 100644
--- a/fs/netfs/write_issue.c
+++ b/fs/netfs/write_issue.c
@@ -94,9 +94,10 @@ struct netfs_io_request *netfs_create_write_req(struct address_space *mapping,
{
struct netfs_io_request *wreq;
struct netfs_inode *ictx;
- bool is_buffered = (origin == NETFS_WRITEBACK ||
- origin == NETFS_WRITETHROUGH ||
- origin == NETFS_PGPRIV2_COPY_TO_CACHE);
+ bool is_cacheable = (origin == NETFS_WRITEBACK ||
+ origin == NETFS_WRITEBACK_SINGLE ||
+ origin == NETFS_WRITETHROUGH ||
+ origin == NETFS_PGPRIV2_COPY_TO_CACHE);

wreq = netfs_alloc_request(mapping, file, start, 0, origin);
if (IS_ERR(wreq))
@@ -105,7 +106,7 @@ struct netfs_io_request *netfs_create_write_req(struct address_space *mapping,
_enter("R=%x", wreq->debug_id);

ictx = netfs_inode(wreq->inode);
- if (is_buffered && netfs_is_cache_enabled(ictx))
+ if (is_cacheable && netfs_is_cache_enabled(ictx))
fscache_begin_write_operation(&wreq->cache_resources, netfs_i_cookie(ictx));
if (rolling_buffer_init(&wreq->buffer, wreq->debug_id, ITER_SOURCE) < 0)
goto nomem;
@@ -450,7 +451,8 @@ static int netfs_write_folio(struct netfs_io_request *wreq,
stream = &wreq->io_streams[s];
stream->submit_off = foff;
stream->submit_len = flen;
- if ((stream->source == NETFS_WRITE_TO_CACHE && streamw) ||
+ if (!stream->avail ||
+ (stream->source == NETFS_WRITE_TO_CACHE && streamw) ||
(stream->source == NETFS_UPLOAD_TO_SERVER &&
fgroup == NETFS_FOLIO_COPY_TO_CACHE)) {
stream->submit_off = UINT_MAX;
@@ -729,3 +731,194 @@ int netfs_unbuffered_write(struct netfs_io_request *wreq, bool may_wait, size_t
_leave(" = %d", error);
return error;
}
+
+/*
+ * Write some of a pending folio data back to the server and/or the cache.
+ */
+static int netfs_write_folio_single(struct netfs_io_request *wreq,
+ struct folio *folio)
+{
+ struct netfs_io_stream *upload = &wreq->io_streams[0];
+ struct netfs_io_stream *cache = &wreq->io_streams[1];
+ struct netfs_io_stream *stream;
+ size_t iter_off = 0;
+ size_t fsize = folio_size(folio), flen;
+ loff_t fpos = folio_pos(folio);
+ bool to_eof = false;
+ bool no_debug = false;
+
+ _enter("");
+
+ flen = folio_size(folio);
+ if (flen > wreq->i_size - fpos) {
+ flen = wreq->i_size - fpos;
+ folio_zero_segment(folio, flen, fsize);
+ to_eof = true;
+ } else if (flen == wreq->i_size - fpos) {
+ to_eof = true;
+ }
+
+ _debug("folio %zx/%zx", flen, fsize);
+
+ if (!upload->avail && !cache->avail) {
+ trace_netfs_folio(folio, netfs_folio_trace_cancel_store);
+ return 0;
+ }
+
+ if (!upload->construct)
+ trace_netfs_folio(folio, netfs_folio_trace_store);
+ else
+ trace_netfs_folio(folio, netfs_folio_trace_store_plus);
+
+ /* Attach the folio to the rolling buffer. */
+ folio_get(folio);
+ rolling_buffer_append(&wreq->buffer, folio, NETFS_ROLLBUF_PUT_MARK);
+
+ /* Move the submission point forward to allow for write-streaming data
+ * not starting at the front of the page. We don't do write-streaming
+ * with the cache as the cache requires DIO alignment.
+ *
+ * Also skip uploading for data that's been read and just needs copying
+ * to the cache.
+ */
+ for (int s = 0; s < NR_IO_STREAMS; s++) {
+ stream = &wreq->io_streams[s];
+ stream->submit_off = 0;
+ stream->submit_len = flen;
+ if (!stream->avail) {
+ stream->submit_off = UINT_MAX;
+ stream->submit_len = 0;
+ }
+ }
+
+ /* Attach the folio to one or more subrequests. For a big folio, we
+ * could end up with thousands of subrequests if the wsize is small -
+ * but we might need to wait during the creation of subrequests for
+ * network resources (eg. SMB credits).
+ */
+ for (;;) {
+ ssize_t part;
+ size_t lowest_off = ULONG_MAX;
+ int choose_s = -1;
+
+ /* Always add to the lowest-submitted stream first. */
+ for (int s = 0; s < NR_IO_STREAMS; s++) {
+ stream = &wreq->io_streams[s];
+ if (stream->submit_len > 0 &&
+ stream->submit_off < lowest_off) {
+ lowest_off = stream->submit_off;
+ choose_s = s;
+ }
+ }
+
+ if (choose_s < 0)
+ break;
+ stream = &wreq->io_streams[choose_s];
+
+ /* Advance the iterator(s). */
+ if (stream->submit_off > iter_off) {
+ rolling_buffer_advance(&wreq->buffer, stream->submit_off - iter_off);
+ iter_off = stream->submit_off;
+ }
+
+ atomic64_set(&wreq->issued_to, fpos + stream->submit_off);
+ stream->submit_extendable_to = fsize - stream->submit_off;
+ part = netfs_advance_write(wreq, stream, fpos + stream->submit_off,
+ stream->submit_len, to_eof);
+ stream->submit_off += part;
+ if (part > stream->submit_len)
+ stream->submit_len = 0;
+ else
+ stream->submit_len -= part;
+ if (part > 0)
+ no_debug = true;
+ }
+
+ wreq->buffer.iter.iov_offset = 0;
+ if (fsize > iter_off)
+ rolling_buffer_advance(&wreq->buffer, fsize - iter_off);
+ atomic64_set(&wreq->issued_to, fpos + fsize);
+
+ if (!no_debug)
+ kdebug("R=%x: No submit", wreq->debug_id);
+ _leave(" = 0");
+ return 0;
+}
+
+/**
+ * netfs_writeback_single - Write back a monolithic payload
+ * @mapping: The mapping to write from
+ * @wbc: Hints from the VM
+ * @iter: Data to write, must be ITER_FOLIOQ.
+ *
+ * Write a monolithic, non-pagecache object back to the server and/or
+ * the cache.
+ */
+int netfs_writeback_single(struct address_space *mapping,
+ struct writeback_control *wbc,
+ struct iov_iter *iter)
+{
+ struct netfs_io_request *wreq;
+ struct netfs_inode *ictx = netfs_inode(mapping->host);
+ struct folio_queue *fq;
+ size_t size = iov_iter_count(iter);
+ int ret;
+
+ if (WARN_ON_ONCE(!iov_iter_is_folioq(iter)))
+ return -EIO;
+
+ if (!mutex_trylock(&ictx->wb_lock)) {
+ if (wbc->sync_mode == WB_SYNC_NONE) {
+ netfs_stat(&netfs_n_wb_lock_skip);
+ return 0;
+ }
+ netfs_stat(&netfs_n_wb_lock_wait);
+ mutex_lock(&ictx->wb_lock);
+ }
+
+ wreq = netfs_create_write_req(mapping, NULL, 0, NETFS_WRITEBACK_SINGLE);
+ if (IS_ERR(wreq)) {
+ ret = PTR_ERR(wreq);
+ goto couldnt_start;
+ }
+
+ trace_netfs_write(wreq, netfs_write_trace_writeback);
+ netfs_stat(&netfs_n_wh_writepages);
+
+ if (__test_and_set_bit(NETFS_RREQ_UPLOAD_TO_SERVER, &wreq->flags))
+ wreq->netfs_ops->begin_writeback(wreq);
+
+ for (fq = (struct folio_queue *)iter->folioq; fq; fq = fq->next) {
+ for (int slot = 0; slot < folioq_count(fq); slot++) {
+ struct folio *folio = folioq_folio(fq, slot);
+ size_t part = umin(folioq_folio_size(fq, slot), size);
+
+ _debug("wbiter %lx %llx", folio->index, atomic64_read(&wreq->issued_to));
+
+ ret = netfs_write_folio_single(wreq, folio);
+ if (ret < 0)
+ goto stop;
+ size -= part;
+ if (size <= 0)
+ goto stop;
+ }
+ }
+
+stop:
+ for (int s = 0; s < NR_IO_STREAMS; s++)
+ netfs_issue_write(wreq, &wreq->io_streams[s]);
+ smp_wmb(); /* Write lists before ALL_QUEUED. */
+ set_bit(NETFS_RREQ_ALL_QUEUED, &wreq->flags);
+
+ mutex_unlock(&ictx->wb_lock);
+
+ netfs_put_request(wreq, false, netfs_rreq_trace_put_return);
+ _leave(" = %d", ret);
+ return ret;
+
+couldnt_start:
+ mutex_unlock(&ictx->wb_lock);
+ _leave(" = %d", ret);
+ return ret;
+}
+EXPORT_SYMBOL(netfs_writeback_single);
diff --git a/include/linux/netfs.h b/include/linux/netfs.h
index 921cfcfc62f1..5e21c6939c88 100644
--- a/include/linux/netfs.h
+++ b/include/linux/netfs.h
@@ -73,6 +73,7 @@ struct netfs_inode {
#define NETFS_ICTX_UNBUFFERED 1 /* I/O should not use the pagecache */
#define NETFS_ICTX_WRITETHROUGH 2 /* Write-through caching */
#define NETFS_ICTX_MODIFIED_ATTR 3 /* Indicate change in mtime/ctime */
+#define NETFS_ICTX_SINGLE_NO_UPLOAD 4 /* Monolithic payload, cache but no upload */
};

/*
@@ -210,9 +211,11 @@ enum netfs_io_origin {
NETFS_READAHEAD, /* This read was triggered by readahead */
NETFS_READPAGE, /* This read is a synchronous read */
NETFS_READ_GAPS, /* This read is a synchronous read to fill gaps */
+ NETFS_READ_SINGLE, /* This read should be treated as a single object */
NETFS_READ_FOR_WRITE, /* This read is to prepare a write */
NETFS_DIO_READ, /* This is a direct I/O read */
NETFS_WRITEBACK, /* This write was triggered by writepages */
+ NETFS_WRITEBACK_SINGLE, /* This monolithic write was triggered by writepages */
NETFS_WRITETHROUGH, /* This write was made by netfs_perform_write() */
NETFS_UNBUFFERED_WRITE, /* This is an unbuffered write */
NETFS_DIO_WRITE, /* This is a direct I/O write */
@@ -409,6 +412,13 @@ ssize_t netfs_unbuffered_write_iter_locked(struct kiocb *iocb, struct iov_iter *
struct netfs_group *netfs_group);
ssize_t netfs_file_write_iter(struct kiocb *iocb, struct iov_iter *from);

+/* Single, monolithic object read/write API. */
+void netfs_single_mark_inode_dirty(struct inode *inode);
+ssize_t netfs_read_single(struct inode *inode, struct file *file, struct iov_iter *iter);
+int netfs_writeback_single(struct address_space *mapping,
+ struct writeback_control *wbc,
+ struct iov_iter *iter);
+
/* Address operations API */
struct readahead_control;
void netfs_readahead(struct readahead_control *);
diff --git a/include/trace/events/netfs.h b/include/trace/events/netfs.h
index 167c89bc62e0..e8075c29ecf5 100644
--- a/include/trace/events/netfs.h
+++ b/include/trace/events/netfs.h
@@ -21,6 +21,7 @@
EM(netfs_read_trace_readahead, "READAHEAD") \
EM(netfs_read_trace_readpage, "READPAGE ") \
EM(netfs_read_trace_read_gaps, "READ-GAPS") \
+ EM(netfs_read_trace_read_single, "READ-SNGL") \
EM(netfs_read_trace_prefetch_for_write, "PREFETCHW") \
E_(netfs_read_trace_write_begin, "WRITEBEGN")

@@ -35,9 +36,11 @@
EM(NETFS_READAHEAD, "RA") \
EM(NETFS_READPAGE, "RP") \
EM(NETFS_READ_GAPS, "RG") \
+ EM(NETFS_READ_SINGLE, "R1") \
EM(NETFS_READ_FOR_WRITE, "RW") \
EM(NETFS_DIO_READ, "DR") \
EM(NETFS_WRITEBACK, "WB") \
+ EM(NETFS_WRITEBACK_SINGLE, "W1") \
EM(NETFS_WRITETHROUGH, "WT") \
EM(NETFS_UNBUFFERED_WRITE, "UW") \
EM(NETFS_DIO_WRITE, "DW") \
@@ -47,6 +50,7 @@
EM(netfs_rreq_trace_assess, "ASSESS ") \
EM(netfs_rreq_trace_copy, "COPY ") \
EM(netfs_rreq_trace_collect, "COLLECT") \
+ EM(netfs_rreq_trace_dirty, "DIRTY ") \
EM(netfs_rreq_trace_done, "DONE ") \
EM(netfs_rreq_trace_free, "FREE ") \
EM(netfs_rreq_trace_redirty, "REDIRTY") \