RE: [PATCH 19/26] netfs: New writeback implementation

Naveen Mamindlapalli
2024-03-29T10:36:37Z

> -----Original Message-----
> From: David Howells <dhowells@redhat.com>
> Sent: Thursday, March 28, 2024 10:04 PM
> To: Christian Brauner <christian@brauner.io>; Jeff Layton <jlayton@kernel.org>;
> Gao Xiang <hsiangkao@linux.alibaba.com>; Dominique Martinet
> <asmadeus@codewreck.org>
> Cc: David Howells <dhowells@redhat.com>; Matthew Wilcox
> <willy@infradead.org>; Steve French <smfrench@gmail.com>; Marc Dionne
> <marc.dionne@auristor.com>; Paulo Alcantara <pc@manguebit.com>; Shyam
> Prasad N <sprasad@microsoft.com>; Tom Talpey <tom@talpey.com>; Eric Van
> Hensbergen <ericvh@kernel.org>; Ilya Dryomov <idryomov@gmail.com>;
> netfs@lists.linux.dev; linux-cachefs@redhat.com; linux-afs@lists.infradead.org;
> linux-cifs@vger.kernel.org; linux-nfs@vger.kernel.org; ceph-
> devel@vger.kernel.org; v9fs@lists.linux.dev; linux-erofs@lists.ozlabs.org; linux-
> fsdevel@vger.kernel.org; linux-mm@kvack.org; netdev@vger.kernel.org; linux-
> kernel@vger.kernel.org; Latchesar Ionkov <lucho@ionkov.net>; Christian
> Schoenebeck <linux_oss@crudebyte.com>
> Subject: [PATCH 19/26] netfs: New writeback implementation
>
> The current netfslib writeback implementation creates writeback requests of
> contiguous folio data and then separately tiles subrequests over the space
> twice, once for the server and once for the cache. This creates a few
> issues:
>
> (1) Every time there's a discontiguity or a change between writing to only
> one destination or writing to both, it must create a new request.
> This makes it harder to do vectored writes.
>
> (2) The folios don't have the writeback mark removed until the end of the
> request - and a request could be hundreds of megabytes.
>
> (3) In future, I want to support a larger cache granularity, which will
> require aggregation of some folios that contain unmodified data (which
> only need to go to the cache) and some which contain modifications
> (which need to be uploaded and stored to the cache) - but, currently,
> these are treated as discontiguous.
>
> There's also a move to get everyone to use writeback_iter() to extract
> writable folios from the pagecache. That said, currently writeback_iter()
> has some issues that make it less than ideal:
>
> (1) there's no way to cancel the iteration, even if you find a "temporary"
> error that means the current folio and all subsequent folios are going
> to fail;
>
> (2) there's no way to filter the folios being written back - something
> that will impact Ceph with it's ordered snap system;
>
> (3) and if you get a folio you can't immediately deal with (say you need
> to flush the preceding writes), you are left with a folio hanging in
> the locked state for the duration, when really we should unlock it and
> relock it later.
>
> In this new implementation, I use writeback_iter() to pump folios,
> progressively creating two parallel, but separate streams and cleaning up
> the finished folios as the subrequests complete. Either or both streams
> can contain gaps, and the subrequests in each stream can be of variable
> size, don't need to align with each other and don't need to align with the
> folios.
>
> Indeed, subrequests can cross folio boundaries, may cover several folios or
> a folio may be spanned by multiple folios, e.g.:
>
> +---+---+-----+-----+---+----------+
> Folios: | | | | | | |
> +---+---+-----+-----+---+----------+
>
> +------+------+ +----+----+
> Upload: | | |.....| | |
> +------+------+ +----+----+
>
> +------+------+------+------+------+
> Cache: | | | | | |
> +------+------+------+------+------+
>
> The progressive subrequest construction permits the algorithm to be
> preparing both the next upload to the server and the next write to the
> cache whilst the previous ones are already in progress. Throttling can be
> applied to control the rate of production of subrequests - and, in any
> case, we probably want to write them to the server in ascending order,
> particularly if the file will be extended.
>
> Content crypto can also be prepared at the same time as the subrequests and
> run asynchronously, with the prepped requests being stalled until the
> crypto catches up with them. This might also be useful for transport
> crypto, but that happens at a lower layer, so probably would be harder to
> pull off.
>
> The algorithm is split into three parts:
>
> (1) The issuer. This walks through the data, packaging it up, encrypting
> it and creating subrequests. The part of this that generates
> subrequests only deals with file positions and spans and so is usable
> for DIO/unbuffered writes as well as buffered writes.
>
> (2) The collector. This asynchronously collects completed subrequests,
> unlocks folios, frees crypto buffers and performs any retries. This
> runs in a work queue so that the issuer can return to the caller for
> writeback (so that the VM can have its kswapd thread back) or async
> writes.
>
> (3) The retryer. This pauses the issuer, waits for all outstanding
> subrequests to complete and then goes through the failed subrequests
> to reissue them. This may involve reprepping them (with cifs, the
> credits must be renegotiated, and a subrequest may need splitting),
> and doing RMW for content crypto if there's a conflicting change on
> the server.
>
> [!] Note that some of the functions are prefixed with "new_" to avoid
> clashes with existing functions. These will be renamed in a later patch
> that cuts over to the new algorithm.
>
> Signed-off-by: David Howells <dhowells@redhat.com>
> cc: Jeff Layton <jlayton@kernel.org>
> cc: Eric Van Hensbergen <ericvh@kernel.org>
> cc: Latchesar Ionkov <lucho@ionkov.net>
> cc: Dominique Martinet <asmadeus@codewreck.org>
> cc: Christian Schoenebeck <linux_oss@crudebyte.com>
> cc: Marc Dionne <marc.dionne@auristor.com>
> cc: v9fs@lists.linux.dev
> cc: linux-afs@lists.infradead.org
> cc: netfs@lists.linux.dev
> cc: linux-fsdevel@vger.kernel.org
> ---
> fs/netfs/Makefile | 4 +-
> fs/netfs/buffered_write.c | 4 -
> fs/netfs/internal.h | 27 ++
> fs/netfs/objects.c | 17 +
> fs/netfs/write_collect.c | 808 +++++++++++++++++++++++++++++++++++
> fs/netfs/write_issue.c | 673 +++++++++++++++++++++++++++++
> include/linux/netfs.h | 68 ++-
> include/trace/events/netfs.h | 232 +++++++++-
> 8 files changed, 1824 insertions(+), 9 deletions(-)
> create mode 100644 fs/netfs/write_collect.c
> create mode 100644 fs/netfs/write_issue.c
>
> diff --git a/fs/netfs/Makefile b/fs/netfs/Makefile
> index d4d1d799819e..1eb86e34b5a9 100644
> --- a/fs/netfs/Makefile
> +++ b/fs/netfs/Makefile
> @@ -11,7 +11,9 @@ netfs-y := \
> main.o \
> misc.o \
> objects.o \
> - output.o
> + output.o \
> + write_collect.o \
> + write_issue.o
>
> netfs-$(CONFIG_NETFS_STATS) += stats.o
>
> diff --git a/fs/netfs/buffered_write.c b/fs/netfs/buffered_write.c
> index 244d67a43972..621532dacef5 100644
> --- a/fs/netfs/buffered_write.c
> +++ b/fs/netfs/buffered_write.c
> @@ -74,16 +74,12 @@ static enum netfs_how_to_modify
> netfs_how_to_modify(struct netfs_inode *ctx,
>
> if (file->f_mode & FMODE_READ)
> goto no_write_streaming;
> - if (test_bit(NETFS_ICTX_NO_WRITE_STREAMING, &ctx->flags))
> - goto no_write_streaming;
>
> if (netfs_is_cache_enabled(ctx)) {
> /* We don't want to get a streaming write on a file that loses
> * caching service temporarily because the backing store got
> * culled.
> */
> - if (!test_bit(NETFS_ICTX_NO_WRITE_STREAMING, &ctx-
> >flags))
> - set_bit(NETFS_ICTX_NO_WRITE_STREAMING, &ctx-
> >flags);
> goto no_write_streaming;
> }
>
> diff --git a/fs/netfs/internal.h b/fs/netfs/internal.h
> index 58289cc65e25..5d3f74a70fa7 100644
> --- a/fs/netfs/internal.h
> +++ b/fs/netfs/internal.h
> @@ -153,6 +153,33 @@ static inline void netfs_stat_d(atomic_t *stat)
> #define netfs_stat_d(x) do {} while(0)
> #endif
>
> +/*
> + * write_collect.c
> + */
> +int netfs_folio_written_back(struct folio *folio);
> +void netfs_write_collection_worker(struct work_struct *work);
> +void netfs_wake_write_collector(struct netfs_io_request *wreq, bool
> was_async);
> +
> +/*
> + * write_issue.c
> + */
> +struct netfs_io_request *netfs_create_write_req(struct address_space *mapping,
> + struct file *file,
> + loff_t start,
> + enum netfs_io_origin origin);
> +void netfs_reissue_write(struct netfs_io_stream *stream,
> + struct netfs_io_subrequest *subreq);
> +int netfs_advance_write(struct netfs_io_request *wreq,
> + struct netfs_io_stream *stream,
> + loff_t start, size_t len, bool to_eof);
> +struct netfs_io_request *new_netfs_begin_writethrough(struct kiocb *iocb, size_t
> len);
> +int new_netfs_advance_writethrough(struct netfs_io_request *wreq, struct
> writeback_control *wbc,
> + struct folio *folio, size_t copied, bool
> to_page_end,
> + struct folio **writethrough_cache);
> +int new_netfs_end_writethrough(struct netfs_io_request *wreq, struct
> writeback_control *wbc,
> + struct folio *writethrough_cache);
> +int netfs_unbuffered_write(struct netfs_io_request *wreq, bool may_wait, size_t
> len);
> +
> /*
> * Miscellaneous functions.
> */
> diff --git a/fs/netfs/objects.c b/fs/netfs/objects.c
> index 1a4e2ce735ce..c90d482b1650 100644
> --- a/fs/netfs/objects.c
> +++ b/fs/netfs/objects.c
> @@ -47,6 +47,10 @@ struct netfs_io_request *netfs_alloc_request(struct
> address_space *mapping,
> rreq->inode = inode;
> rreq->i_size = i_size_read(inode);
> rreq->debug_id = atomic_inc_return(&debug_ids);
> + rreq->wsize = INT_MAX;
> + spin_lock_init(&rreq->lock);
> + INIT_LIST_HEAD(&rreq->io_streams[0].subrequests);
> + INIT_LIST_HEAD(&rreq->io_streams[1].subrequests);
> INIT_LIST_HEAD(&rreq->subrequests);
> INIT_WORK(&rreq->work, NULL);
> refcount_set(&rreq->ref, 1);
> @@ -85,6 +89,8 @@ void netfs_get_request(struct netfs_io_request *rreq, enum
> netfs_rreq_ref_trace
> void netfs_clear_subrequests(struct netfs_io_request *rreq, bool was_async)
> {
> struct netfs_io_subrequest *subreq;
> + struct netfs_io_stream *stream;
> + int s;
>
> while (!list_empty(&rreq->subrequests)) {
> subreq = list_first_entry(&rreq->subrequests,
> @@ -93,6 +99,17 @@ void netfs_clear_subrequests(struct netfs_io_request
> *rreq, bool was_async)
> netfs_put_subrequest(subreq, was_async,
> netfs_sreq_trace_put_clear);
> }
> +
> + for (s = 0; s < ARRAY_SIZE(rreq->io_streams); s++) {
> + stream = &rreq->io_streams[s];
> + while (!list_empty(&stream->subrequests)) {
> + subreq = list_first_entry(&stream->subrequests,
> + struct netfs_io_subrequest,
> rreq_link);
> + list_del(&subreq->rreq_link);
> + netfs_put_subrequest(subreq, was_async,
> + netfs_sreq_trace_put_clear);
> + }
> + }
> }
>
> static void netfs_free_request_rcu(struct rcu_head *rcu)
> diff --git a/fs/netfs/write_collect.c b/fs/netfs/write_collect.c
> new file mode 100644
> index 000000000000..5e2ca8b25af0
> --- /dev/null
> +++ b/fs/netfs/write_collect.c
> @@ -0,0 +1,808 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/* Network filesystem write subrequest result collection, assessment
> + * and retrying.
> + *
> + * 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 "internal.h"
> +
> +/* Notes made in the collector */
> +#define HIT_PENDING 0x01 /* A front op was still pending */
> +#define SOME_EMPTY 0x02 /* One of more streams are empty
> */
> +#define ALL_EMPTY 0x04 /* All streams are empty */
> +#define MAYBE_DISCONTIG 0x08 /* A front op may be
> discontiguous (rounded to PAGE_SIZE) */
> +#define NEED_REASSESS 0x10 /* Need to loop round and
> reassess */
> +#define REASSESS_DISCONTIG 0x20 /* Reassess discontiguity if
> contiguity advances */
> +#define MADE_PROGRESS 0x40 /* Made progress cleaning up a
> stream or the folio set */
> +#define BUFFERED 0x80 /* The pagecache needs cleaning up */
> +#define NEED_RETRY 0x100 /* A front op requests retrying */
> +#define SAW_FAILURE 0x200 /* One stream or hit a permanent
> failure */
> +
> +/*
> + * Successful completion of write of a folio to the server and/or cache. Note
> + * that we are not allowed to lock the folio here on pain of deadlocking with
> + * truncate.
> + */
> +int netfs_folio_written_back(struct folio *folio)
> +{
> + enum netfs_folio_trace why = netfs_folio_trace_clear;
> + struct netfs_folio *finfo;
> + struct netfs_group *group = NULL;
> + int gcount = 0;

Reverse xmas tree order missing in multiple functions.

> +
> + if ((finfo = netfs_folio_info(folio))) {
> + /* Streaming writes cannot be redirtied whilst under writeback,
> + * so discard the streaming record.
> + */
> + folio_detach_private(folio);
> + group = finfo->netfs_group;
> + gcount++;
> + kfree(finfo);
> + why = netfs_folio_trace_clear_s;
> + goto end_wb;
> + }
> +
> + if ((group = netfs_folio_group(folio))) {
> + if (group == NETFS_FOLIO_COPY_TO_CACHE) {
> + why = netfs_folio_trace_clear_cc;
> + if (group == NETFS_FOLIO_COPY_TO_CACHE)
> + folio_detach_private(folio);
> + else
> + why = netfs_folio_trace_redirtied;
> + goto end_wb;
> + }
> +
> + /* Need to detach the group pointer if the page didn't get
> + * redirtied. If it has been redirtied, then it must be within
> + * the same group.
> + */
> + why = netfs_folio_trace_redirtied;
> + if (!folio_test_dirty(folio)) {
> + if (!folio_test_dirty(folio)) {
> + folio_detach_private(folio);
> + gcount++;
> + why = netfs_folio_trace_clear_g;
> + }
> + }
> + }
> +
> +end_wb:
> + trace_netfs_folio(folio, why);
> + folio_end_writeback(folio);
> + return gcount;
> +}
> +
> +/*
> + * Get hold of a folio we have under writeback. We don't want to get the
> + * refcount on it.
> + */
> +static struct folio *netfs_writeback_lookup_folio(struct netfs_io_request *wreq,
> loff_t pos)
> +{
> + XA_STATE(xas, &wreq->mapping->i_pages, pos / PAGE_SIZE);
> + struct folio *folio;
> +
> + rcu_read_lock();
> +
> + for (;;) {
> + xas_reset(&xas);
> + folio = xas_load(&xas);
> + if (xas_retry(&xas, folio))
> + continue;
> +
> + if (!folio || xa_is_value(folio))
> + kdebug("R=%08x: folio %lx (%llx) not present",
> + wreq->debug_id, xas.xa_index, pos / PAGE_SIZE);
> + BUG_ON(!folio || xa_is_value(folio));
> +
> + if (folio == xas_reload(&xas))
> + break;
> + }
> +
> + rcu_read_unlock();
> +
> + if (WARN_ONCE(!folio_test_writeback(folio),
> + "R=%08x: folio %lx is not under writeback\n",
> + wreq->debug_id, folio->index)) {
> + trace_netfs_folio(folio, netfs_folio_trace_not_under_wback);
> + }
> + return folio;
> +}
> +
> +/*
> + * Unlock any folios we've finished with.
> + */
> +static void netfs_writeback_unlock_folios(struct netfs_io_request *wreq,
> + unsigned long long collected_to,
> + unsigned int *notes)
> +{
> + for (;;) {
> + struct folio *folio;
> + struct netfs_folio *finfo;
> + unsigned long long fpos, fend;
> + size_t fsize, flen;
> +
> + folio = netfs_writeback_lookup_folio(wreq, wreq->cleaned_to);
> +
> + fpos = folio_pos(folio);
> + fsize = folio_size(folio);
> + finfo = netfs_folio_info(folio);
> + flen = finfo ? finfo->dirty_offset + finfo->dirty_len : fsize;
> +
> + fend = min_t(unsigned long long, fpos + flen, wreq->i_size);
> +
> + trace_netfs_collect_folio(wreq, folio, fend, collected_to);
> +
> + if (fpos + fsize > wreq->contiguity) {
> + trace_netfs_collect_contig(wreq, fpos + fsize,
> + netfs_contig_trace_unlock);
> + wreq->contiguity = fpos + fsize;
> + }
> +
> + /* Unlock any folio we've transferred all of. */
> + if (collected_to < fend)
> + break;
> +
> + wreq->nr_group_rel += netfs_folio_written_back(folio);
> + wreq->cleaned_to = fpos + fsize;
> + *notes |= MADE_PROGRESS;
> +
> + if (fpos + fsize >= collected_to)
> + break;
> + }
> +}
> +
> +/*
> + * Perform retries on the streams that need it.
> + */
> +static void netfs_retry_write_stream(struct netfs_io_request *wreq,
> + struct netfs_io_stream *stream)
> +{
> + struct list_head *next;
> +
> + _enter("R=%x[%x:]", wreq->debug_id, stream->stream_nr);
> +
> + if (unlikely(stream->failed))
> + return;
> +
> + /* If there's no renegotiation to do, just resend each failed subreq. */
> + if (!stream->prepare_write) {
> + struct netfs_io_subrequest *subreq;
> +
> + list_for_each_entry(subreq, &stream->subrequests, rreq_link) {
> + if (test_bit(NETFS_SREQ_FAILED, &subreq->flags))
> + break;
> + if (__test_and_clear_bit(NETFS_SREQ_NEED_RETRY,
> &subreq->flags)) {
> + __set_bit(NETFS_SREQ_RETRYING, &subreq-
> >flags);
> + netfs_get_subrequest(subreq,
> netfs_sreq_trace_get_resubmit);
> + netfs_reissue_write(stream, subreq);
> + }
> + }
> + return;
> + }
> +
> + if (list_empty(&stream->subrequests))
> + return;
> + next = stream->subrequests.next;
> +
> + do {
> + struct netfs_io_subrequest *subreq = NULL, *from, *to, *tmp;
> + unsigned long long start, len;
> + size_t part;
> + bool boundary = false;
> +
> + /* Go through the stream and find the next span of contiguous
> + * data that we then rejig (cifs, for example, needs the wsize
> + * renegotiating) and reissue.
> + */
> + from = list_entry(next, struct netfs_io_subrequest, rreq_link);
> + to = from;
> + start = from->start + from->transferred;
> + len = from->len - from->transferred;
> +
> + if (test_bit(NETFS_SREQ_FAILED, &from->flags) ||
> + !test_bit(NETFS_SREQ_NEED_RETRY, &from->flags))
> + return;
> +
> + list_for_each_continue(next, &stream->subrequests) {
> + subreq = list_entry(next, struct netfs_io_subrequest,
> rreq_link);
> + if (subreq->start + subreq->transferred != start + len ||
> + test_bit(NETFS_SREQ_BOUNDARY, &subreq->flags)
> ||
> + !test_bit(NETFS_SREQ_NEED_RETRY, &subreq-
> >flags))
> + break;
> + to = subreq;
> + len += to->len;
> + }
> +
> + /* Work through the sublist. */
> + subreq = from;
> + list_for_each_entry_from(subreq, &stream->subrequests,
> rreq_link) {
> + if (!len)
> + break;
> + /* Renegotiate max_len (wsize) */
> + trace_netfs_sreq(subreq, netfs_sreq_trace_retry);
> + __clear_bit(NETFS_SREQ_NEED_RETRY, &subreq-
> >flags);
> + __set_bit(NETFS_SREQ_RETRYING, &subreq->flags);
> + stream->prepare_write(subreq);
> +
> + part = min(len, subreq->max_len);
> + subreq->len = part;
> + subreq->start = start;
> + subreq->transferred = 0;
> + len -= part;
> + start += part;
> + if (len && subreq == to &&
> + __test_and_clear_bit(NETFS_SREQ_BOUNDARY, &to-
> >flags))
> + boundary = true;
> +
> + netfs_get_subrequest(subreq,
> netfs_sreq_trace_get_resubmit);
> + netfs_reissue_write(stream, subreq);
> + if (subreq == to)
> + break;
> + }
> +
> + /* If we managed to use fewer subreqs, we can discard the
> + * excess; if we used the same number, then we're done.
> + */
> + if (!len) {
> + if (subreq == to)
> + continue;
> + list_for_each_entry_safe_from(subreq, tmp,
> + &stream->subrequests,
> rreq_link) {
> + trace_netfs_sreq(subreq,
> netfs_sreq_trace_discard);
> + list_del(&subreq->rreq_link);
> + netfs_put_subrequest(subreq, false,
> netfs_sreq_trace_put_done);
> + if (subreq == to)
> + break;
> + }
> + continue;
> + }
> +
> + /* We ran out of subrequests, so we need to allocate some more
> + * and insert them after.
> + */
> + do {
> + subreq = netfs_alloc_subrequest(wreq);
> + subreq->source = to->source;
> + subreq->start = start;
> + subreq->max_len = len;
> + subreq->max_nr_segs = INT_MAX;
> + subreq->debug_index = atomic_inc_return(&wreq-
> >subreq_counter);
> + subreq->stream_nr = to->stream_nr;
> + __set_bit(NETFS_SREQ_RETRYING, &subreq->flags);
> +
> + trace_netfs_sreq_ref(wreq->debug_id, subreq-
> >debug_index,
> + refcount_read(&subreq->ref),
> + netfs_sreq_trace_new);
> + netfs_get_subrequest(subreq,
> netfs_sreq_trace_get_resubmit);
> +
> + list_add(&subreq->rreq_link, &to->rreq_link);
> + to = list_next_entry(to, rreq_link);
> + trace_netfs_sreq(subreq, netfs_sreq_trace_retry);
> +
> + switch (stream->source) {
> + case NETFS_UPLOAD_TO_SERVER:
> + netfs_stat(&netfs_n_wh_upload);
> + subreq->max_len = min(len, wreq->wsize);
> + break;
> + case NETFS_WRITE_TO_CACHE:
> + netfs_stat(&netfs_n_wh_write);
> + break;
> + default:
> + WARN_ON_ONCE(1);
> + }
> +
> + stream->prepare_write(subreq);
> +
> + part = min(len, subreq->max_len);
> + subreq->len = subreq->transferred + part;
> + len -= part;
> + start += part;
> + if (!len && boundary) {
> + __set_bit(NETFS_SREQ_BOUNDARY, &to-
> >flags);
> + boundary = false;
> + }
> +
> + netfs_reissue_write(stream, subreq);
> + if (!len)
> + break;
> +
> + } while (len);
> +
> + } while (!list_is_head(next, &stream->subrequests));
> +}
> +
> +/*
> + * Perform retries on the streams that need it. If we're doing content
> + * encryption and the server copy changed due to a third-party write, we may
> + * need to do an RMW cycle and also rewrite the data to the cache.
> + */
> +static void netfs_retry_writes(struct netfs_io_request *wreq)
> +{
> + struct netfs_io_subrequest *subreq;
> + struct netfs_io_stream *stream;
> + int s;
> +
> + /* Wait for all outstanding I/O to quiesce before performing retries as
> + * we may need to renegotiate the I/O sizes.
> + */
> + for (s = 0; s < NR_IO_STREAMS; s++) {
> + stream = &wreq->io_streams[s];
> + if (!stream->active)
> + continue;
> +
> + list_for_each_entry(subreq, &stream->subrequests, rreq_link) {
> + wait_on_bit(&subreq->flags,
> NETFS_SREQ_IN_PROGRESS,
> + TASK_UNINTERRUPTIBLE);
> + }
> + }
> +
> + // TODO: Enc: Fetch changed partial pages
> + // TODO: Enc: Reencrypt content if needed.
> + // TODO: Enc: Wind back transferred point.
> + // TODO: Enc: Mark cache pages for retry.
> +
> + for (s = 0; s < NR_IO_STREAMS; s++) {
> + stream = &wreq->io_streams[s];
> + if (stream->need_retry) {
> + stream->need_retry = false;
> + netfs_retry_write_stream(wreq, stream);
> + }
> + }
> +}
> +
> +/*
> + * Collect and assess the results of various write subrequests. We may need to
> + * retry some of the results - or even do an RMW cycle for content crypto.
> + *
> + * Note that we have a number of parallel, overlapping lists of subrequests,
> + * one to the server and one to the local cache for example, which may not be
> + * the same size or starting position and may not even correspond in boundary
> + * alignment.
> + */
> +static void netfs_collect_write_results(struct netfs_io_request *wreq)
> +{
> + struct netfs_io_subrequest *front, *remove;
> + struct netfs_io_stream *stream;
> + unsigned long long collected_to;
> + unsigned int notes;
> + int s;
> +
> + _enter("%llx-%llx", wreq->start, wreq->start + wreq->len);
> + trace_netfs_collect(wreq);
> + trace_netfs_rreq(wreq, netfs_rreq_trace_collect);
> +
> +reassess_streams:
> + smp_rmb();
> + collected_to = ULLONG_MAX;
> + if (wreq->origin == NETFS_WRITEBACK)
> + notes = ALL_EMPTY | BUFFERED | MAYBE_DISCONTIG;
> + else if (wreq->origin == NETFS_WRITETHROUGH)
> + notes = ALL_EMPTY | BUFFERED;
> + else
> + notes = ALL_EMPTY;
> +
> + /* Remove completed subrequests from the front of the streams and
> + * advance the completion point on each stream. We stop when we hit
> + * something that's in progress. The issuer thread may be adding stuff
> + * to the tail whilst we're doing this.
> + *
> + * We must not, however, merge in discontiguities that span whole
> + * folios that aren't under writeback. This is made more complicated
> + * by the folios in the gap being of unpredictable sizes - if they even
> + * exist - but we don't want to look them up.
> + */
> + for (s = 0; s < NR_IO_STREAMS; s++) {
> + loff_t rstart, rend;
> +
> + stream = &wreq->io_streams[s];
> + /* Read active flag before list pointers */
> + if (!smp_load_acquire(&stream->active))
> + continue;
> +
> + front = stream->front;
> + while (front) {
> + trace_netfs_collect_sreq(wreq, front);
> + //_debug("sreq [%x] %llx %zx/%zx",
> + // front->debug_index, front->start, front->transferred,
> front->len);
> +
> + /* Stall if there may be a discontinuity. */
> + rstart = round_down(front->start, PAGE_SIZE);
> + if (rstart > wreq->contiguity) {
> + if (wreq->contiguity > stream->collected_to) {
> + trace_netfs_collect_gap(wreq, stream,
> + wreq->contiguity,
> 'D');
> + stream->collected_to = wreq->contiguity;
> + }
> + notes |= REASSESS_DISCONTIG;
> + break;
> + }
> + rend = round_up(front->start + front->len, PAGE_SIZE);
> + if (rend > wreq->contiguity) {
> + trace_netfs_collect_contig(wreq, rend,
> +
> netfs_contig_trace_collect);
> + wreq->contiguity = rend;
> + if (notes & REASSESS_DISCONTIG)
> + notes |= NEED_REASSESS;
> + }
> + notes &= ~MAYBE_DISCONTIG;
> +
> + /* Stall if the front is still undergoing I/O. */
> + if (test_bit(NETFS_SREQ_IN_PROGRESS, &front-
> >flags)) {
> + notes |= HIT_PENDING;
> + break;
> + }
> + smp_rmb(); /* Read counters after I-P flag. */
> +
> + if (stream->failed) {
> + stream->collected_to = front->start + front->len;
> + notes |= MADE_PROGRESS | SAW_FAILURE;
> + goto cancel;
> + }
> + if (front->start + front->transferred > stream-
> >collected_to) {
> + stream->collected_to = front->start + front-
> >transferred;
> + stream->transferred = stream->collected_to -
> wreq->start;
> + notes |= MADE_PROGRESS;
> + }
> + if (test_bit(NETFS_SREQ_FAILED, &front->flags)) {
> + stream->failed = true;
> + stream->error = front->error;
> + if (stream->source ==
> NETFS_UPLOAD_TO_SERVER)
> + mapping_set_error(wreq->mapping, front-
> >error);
> + notes |= NEED_REASSESS | SAW_FAILURE;
> + break;
> + }
> + if (front->transferred < front->len) {
> + stream->need_retry = true;
> + notes |= NEED_RETRY | MADE_PROGRESS;
> + break;
> + }
> +
> + cancel:
> + /* Remove if completely consumed. */
> + spin_lock(&wreq->lock);
> +
> + remove = front;
> + list_del_init(&front->rreq_link);
> + front = list_first_entry_or_null(&stream->subrequests,
> + struct
> netfs_io_subrequest, rreq_link);
> + stream->front = front;
> + if (!front) {
> + unsigned long long jump_to =
> atomic64_read(&wreq->issued_to);
> +
> + if (stream->collected_to < jump_to) {
> + trace_netfs_collect_gap(wreq, stream,
> jump_to, 'A');
> + stream->collected_to = jump_to;
> + }
> + }
> +
> + spin_unlock(&wreq->lock);
> + netfs_put_subrequest(remove, false,
> + notes & SAW_FAILURE ?
> + netfs_sreq_trace_put_cancel :
> + netfs_sreq_trace_put_done);
> + }
> +
> + if (front)
> + notes &= ~ALL_EMPTY;
> + else
> + notes |= SOME_EMPTY;
> +
> + if (stream->collected_to < collected_to)
> + collected_to = stream->collected_to;
> + }
> +
> + if (collected_to != ULLONG_MAX && collected_to > wreq->collected_to)
> + wreq->collected_to = collected_to;
> +
> + /* If we have an empty stream, we need to jump it forward over any gap
> + * otherwise the collection point will never advance.
> + *
> + * Note that the issuer always adds to the stream with the lowest
> + * so-far submitted start, so if we see two consecutive subreqs in one
> + * stream with nothing between then in another stream, then the second
> + * stream has a gap that can be jumped.
> + */
> + if (notes & SOME_EMPTY) {
> + unsigned long long jump_to = wreq->start + wreq->len;
> +
> + for (s = 0; s < NR_IO_STREAMS; s++) {
> + stream = &wreq->io_streams[s];
> + if (stream->active &&
> + stream->front &&
> + stream->front->start < jump_to)
> + jump_to = stream->front->start;
> + }
> +
> + for (s = 0; s < NR_IO_STREAMS; s++) {
> + stream = &wreq->io_streams[s];
> + if (stream->active &&
> + !stream->front &&
> + stream->collected_to < jump_to) {
> + trace_netfs_collect_gap(wreq, stream, jump_to,
> 'B');
> + stream->collected_to = jump_to;
> + }
> + }
> + }
> +
> + for (s = 0; s < NR_IO_STREAMS; s++) {
> + stream = &wreq->io_streams[s];
> + if (stream->active)
> + trace_netfs_collect_stream(wreq, stream);
> + }
> +
> + trace_netfs_collect_state(wreq, wreq->collected_to, notes);
> +
> + /* Unlock any folios that we have now finished with. */
> + if (notes & BUFFERED) {
> + unsigned long long clean_to = min(wreq->collected_to, wreq-
> >contiguity);
> +
> + if (wreq->cleaned_to < clean_to)
> + netfs_writeback_unlock_folios(wreq, clean_to, &notes);
> + } else {
> + wreq->cleaned_to = wreq->collected_to;
> + }
> +
> + // TODO: Discard encryption buffers
> +
> + /* If all streams are discontiguous with the last folio we cleared, we
> + * may need to skip a set of folios.
> + */
> + if ((notes & (MAYBE_DISCONTIG | ALL_EMPTY)) ==
> MAYBE_DISCONTIG) {
> + unsigned long long jump_to = ULLONG_MAX;
> +
> + for (s = 0; s < NR_IO_STREAMS; s++) {
> + stream = &wreq->io_streams[s];
> + if (stream->active && stream->front &&
> + stream->front->start < jump_to)
> + jump_to = stream->front->start;
> + }
> +
> + trace_netfs_collect_contig(wreq, jump_to,
> netfs_contig_trace_jump);
> + wreq->contiguity = jump_to;
> + wreq->cleaned_to = jump_to;
> + wreq->collected_to = jump_to;
> + for (s = 0; s < NR_IO_STREAMS; s++) {
> + stream = &wreq->io_streams[s];
> + if (stream->collected_to < jump_to)
> + stream->collected_to = jump_to;
> + }
> + //cond_resched();
> + notes |= MADE_PROGRESS;
> + goto reassess_streams;
> + }
> +
> + if (notes & NEED_RETRY)
> + goto need_retry;
> + if ((notes & MADE_PROGRESS) && test_bit(NETFS_RREQ_PAUSE,
> &wreq->flags)) {
> + trace_netfs_rreq(wreq, netfs_rreq_trace_unpause);
> + clear_bit_unlock(NETFS_RREQ_PAUSE, &wreq->flags);
> + wake_up_bit(&wreq->flags, NETFS_RREQ_PAUSE);
> + }
> +
> + if (notes & NEED_REASSESS) {
> + //cond_resched();
> + goto reassess_streams;
> + }
> + if (notes & MADE_PROGRESS) {
> + //cond_resched();
> + goto reassess_streams;
> + }
> +
> +out:
> + netfs_put_group_many(wreq->group, wreq->nr_group_rel);
> + wreq->nr_group_rel = 0;
> + _leave(" = %x", notes);
> + return;
> +
> +need_retry:
> + /* Okay... We're going to have to retry one or both streams. Note
> + * that any partially completed op will have had any wholly transferred
> + * folios removed from it.
> + */
> + _debug("retry");
> + netfs_retry_writes(wreq);
> + goto out;
> +}
> +
> +/*
> + * Perform the collection of subrequests, folios and encryption buffers.
> + */
> +void netfs_write_collection_worker(struct work_struct *work)
> +{
> + struct netfs_io_request *wreq = container_of(work, struct
> netfs_io_request, work);
> + struct netfs_inode *ictx = netfs_inode(wreq->inode);
> + size_t transferred;
> + int s;
> +
> + _enter("R=%x", wreq->debug_id);
> +
> + netfs_see_request(wreq, netfs_rreq_trace_see_work);
> + if (!test_bit(NETFS_RREQ_IN_PROGRESS, &wreq->flags)) {
> + netfs_put_request(wreq, false, netfs_rreq_trace_put_work);
> + return;
> + }
> +
> + netfs_collect_write_results(wreq);
> +
> + /* We're done when the app thread has finished posting subreqs and all
> + * the queues in all the streams are empty.
> + */
> + if (!test_bit(NETFS_RREQ_ALL_QUEUED, &wreq->flags)) {
> + netfs_put_request(wreq, false, netfs_rreq_trace_put_work);
> + return;
> + }
> + smp_rmb(); /* Read ALL_QUEUED before lists. */
> +
> + transferred = LONG_MAX;
> + for (s = 0; s < NR_IO_STREAMS; s++) {
> + struct netfs_io_stream *stream = &wreq->io_streams[s];
> + if (!stream->active)
> + continue;
> + if (!list_empty(&stream->subrequests)) {
> + netfs_put_request(wreq, false,
> netfs_rreq_trace_put_work);
> + return;
> + }
> + if (stream->transferred < transferred)
> + transferred = stream->transferred;
> + }
> +
> + /* Okay, declare that all I/O is complete. */
> + wreq->transferred = transferred;
> + trace_netfs_rreq(wreq, netfs_rreq_trace_write_done);
> +
> + if (wreq->io_streams[1].active &&
> + wreq->io_streams[1].failed) {
> + /* Cache write failure doesn't prevent writeback completion
> + * unless we're in disconnected mode.
> + */
> + ictx->ops->invalidate_cache(wreq);
> + }
> +
> + if (wreq->cleanup)
> + wreq->cleanup(wreq);
> +
> + if (wreq->origin == NETFS_DIO_WRITE &&
> + wreq->mapping->nrpages) {
> + /* mmap may have got underfoot and we may now have folios
> + * locally covering the region we just wrote. Attempt to
> + * discard the folios, but leave in place any modified locally.
> + * ->write_iter() is prevented from interfering by the DIO
> + * counter.
> + */
> + pgoff_t first = wreq->start >> PAGE_SHIFT;
> + pgoff_t last = (wreq->start + wreq->transferred - 1) >>
> PAGE_SHIFT;
> + invalidate_inode_pages2_range(wreq->mapping, first, last);
> + }
> +
> + if (wreq->origin == NETFS_DIO_WRITE)
> + inode_dio_end(wreq->inode);
> +
> + _debug("finished");
> + trace_netfs_rreq(wreq, netfs_rreq_trace_wake_ip);
> + clear_bit_unlock(NETFS_RREQ_IN_PROGRESS, &wreq->flags);
> + wake_up_bit(&wreq->flags, NETFS_RREQ_IN_PROGRESS);
> +
> + if (wreq->iocb) {
> + wreq->iocb->ki_pos += wreq->transferred;
> + if (wreq->iocb->ki_complete)
> + wreq->iocb->ki_complete(
> + wreq->iocb, wreq->error ? wreq->error : wreq-
> >transferred);
> + wreq->iocb = VFS_PTR_POISON;
> + }
> +
> + netfs_clear_subrequests(wreq, false);
> + netfs_put_request(wreq, false, netfs_rreq_trace_put_work_complete);
> +}
> +
> +/*
> + * Wake the collection work item.
> + */
> +void netfs_wake_write_collector(struct netfs_io_request *wreq, bool was_async)
> +{
> + if (!work_pending(&wreq->work)) {
> + netfs_get_request(wreq, netfs_rreq_trace_get_work);
> + if (!queue_work(system_unbound_wq, &wreq->work))
> + netfs_put_request(wreq, was_async,
> netfs_rreq_trace_put_work_nq);
> + }
> +}
> +
> +/**
> + * new_netfs_write_subrequest_terminated - Note the termination of a write
> operation.
> + * @_op: 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 library that a contributory write I/O operation has
> + * terminated, one way or another, and that it should collect 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 or a
> + * negative error code. The library 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.
> + *
> + * When this is called, ownership of the subrequest is transferred back to the
> + * library, along with a ref.
> + *
> + * Note that %_op is a void* so that the function can be passed to
> + * kiocb::term_func without the need for a casting wrapper.
> + */
> +void new_netfs_write_subrequest_terminated(void *_op, ssize_t
> transferred_or_error,
> + bool was_async)
> +{
> + struct netfs_io_subrequest *subreq = _op;
> + struct netfs_io_request *wreq = subreq->rreq;
> + struct netfs_io_stream *stream = &wreq->io_streams[subreq-
> >stream_nr];
> +
> + _enter("%x[%x] %zd", wreq->debug_id, subreq->debug_index,
> transferred_or_error);
> +
> + switch (subreq->source) {
> + case NETFS_UPLOAD_TO_SERVER:
> + netfs_stat(&netfs_n_wh_upload_done);
> + break;
> + case NETFS_WRITE_TO_CACHE:
> + netfs_stat(&netfs_n_wh_write_done);
> + break;
> + case NETFS_INVALID_WRITE:
> + break;
> + default:
> + BUG();
> + }
> +
> + if (IS_ERR_VALUE(transferred_or_error)) {
> + subreq->error = transferred_or_error;
> + if (subreq->error == -EAGAIN)
> + set_bit(NETFS_SREQ_NEED_RETRY, &subreq->flags);
> + else
> + set_bit(NETFS_SREQ_FAILED, &subreq->flags);
> + trace_netfs_failure(wreq, subreq, transferred_or_error,
> netfs_fail_write);
> +
> + switch (subreq->source) {
> + case NETFS_WRITE_TO_CACHE:
> + netfs_stat(&netfs_n_wh_write_failed);
> + break;
> + case NETFS_UPLOAD_TO_SERVER:
> + netfs_stat(&netfs_n_wh_upload_failed);
> + break;
> + default:
> + break;
> + }
> + trace_netfs_rreq(wreq, netfs_rreq_trace_set_pause);
> + set_bit(NETFS_RREQ_PAUSE, &wreq->flags);
> + } else {
> + if (WARN(transferred_or_error > subreq->len - subreq-
> >transferred,
> + "Subreq excess write: R=%x[%x] %zd > %zu - %zu",
> + wreq->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)
> + set_bit(NETFS_SREQ_NEED_RETRY, &subreq->flags);
> + }
> +
> + trace_netfs_sreq(subreq, netfs_sreq_trace_terminated);
> +
> + clear_bit_unlock(NETFS_SREQ_IN_PROGRESS, &subreq->flags);
> + wake_up_bit(&subreq->flags, NETFS_SREQ_IN_PROGRESS);
> +
> + /* If we are at the head of the queue, wake up the collector,
> + * transferring a ref to it if we were the ones to do so.
> + */
> + if (list_is_first(&subreq->rreq_link, &stream->subrequests))
> + netfs_wake_write_collector(wreq, was_async);
> +
> + netfs_put_subrequest(subreq, was_async,
> netfs_sreq_trace_put_terminated);
> +}
> +EXPORT_SYMBOL(new_netfs_write_subrequest_terminated);
> diff --git a/fs/netfs/write_issue.c b/fs/netfs/write_issue.c
> new file mode 100644
> index 000000000000..e0fb472898f5
> --- /dev/null
> +++ b/fs/netfs/write_issue.c
> @@ -0,0 +1,673 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/* Network filesystem high-level (buffered) writeback.
> + *
> + * Copyright (C) 2024 Red Hat, Inc. All Rights Reserved.
> + * Written by David Howells (dhowells@redhat.com)
> + *
> + *
> + * To support network filesystems with local caching, we manage a situation
> + * that can be envisioned like the following:
> + *
> + * +---+---+-----+-----+---+----------+
> + * Folios: | | | | | | |
> + * +---+---+-----+-----+---+----------+
> + *
> + * +------+------+ +----+----+
> + * Upload: | | |.....| | |
> + * (Stream 0) +------+------+ +----+----+
> + *
> + * +------+------+------+------+------+
> + * Cache: | | | | | |
> + * (Stream 1) +------+------+------+------+------+
> + *
> + * Where we have a sequence of folios of varying sizes that we need to overlay
> + * with multiple parallel streams of I/O requests, where the I/O requests in a
> + * stream may also be of various sizes (in cifs, for example, the sizes are
> + * negotiated with the server; in something like ceph, they may represent the
> + * sizes of storage objects).
> + *
> + * The sequence in each stream may contain gaps and noncontiguous
> subrequests
> + * may be glued together into single vectored write RPCs.
> + */
> +
> +#include <linux/export.h>
> +#include <linux/fs.h>
> +#include <linux/mm.h>
> +#include <linux/pagemap.h>
> +#include "internal.h"
> +
> +/*
> + * Kill all dirty folios in the event of an unrecoverable error, starting with
> + * a locked folio we've already obtained from writeback_iter().
> + */
> +static void netfs_kill_dirty_pages(struct address_space *mapping,
> + struct writeback_control *wbc,
> + struct folio *folio)
> +{
> + int error = 0;
> +
> + do {
> + enum netfs_folio_trace why = netfs_folio_trace_kill;
> + struct netfs_group *group = NULL;
> + struct netfs_folio *finfo = NULL;
> + void *priv;
> +
> + priv = folio_detach_private(folio);
> + if (priv) {
> + finfo = __netfs_folio_info(priv);
> + if (finfo) {
> + /* Kill folio from streaming write. */
> + group = finfo->netfs_group;
> + why = netfs_folio_trace_kill_s;
> + } else {
> + group = priv;
> + if (group == NETFS_FOLIO_COPY_TO_CACHE)
> {
> + /* Kill copy-to-cache folio */
> + why = netfs_folio_trace_kill_cc;
> + group = NULL;
> + } else {
> + /* Kill folio with group */
> + why = netfs_folio_trace_kill_g;
> + }
> + }
> + }
> +
> + trace_netfs_folio(folio, why);
> +
> + folio_start_writeback(folio);
> + folio_unlock(folio);
> + folio_end_writeback(folio);
> +
> + netfs_put_group(group);
> + kfree(finfo);
> +
> + } while ((folio = writeback_iter(mapping, wbc, folio, &error)));
> +}
> +
> +/*
> + * Create a write request and set it up appropriately for the origin type.
> + */
> +struct netfs_io_request *netfs_create_write_req(struct address_space *mapping,
> + struct file *file,
> + loff_t start,
> + enum netfs_io_origin origin)
> +{
> + struct netfs_io_request *wreq;
> + struct netfs_inode *ictx;
> +
> + wreq = netfs_alloc_request(mapping, file, start, 0, origin);
> + if (IS_ERR(wreq))
> + return wreq;
> +
> + _enter("R=%x", wreq->debug_id);
> +
> + ictx = netfs_inode(wreq->inode);
> + if (test_bit(NETFS_RREQ_WRITE_TO_CACHE, &wreq->flags))
> + fscache_begin_write_operation(&wreq->cache_resources,
> netfs_i_cookie(ictx));
> +
> + wreq->contiguity = wreq->start;
> + wreq->cleaned_to = wreq->start;
> + INIT_WORK(&wreq->work, netfs_write_collection_worker);
> +
> + wreq->io_streams[0].stream_nr = 0;
> + wreq->io_streams[0].source =
> NETFS_UPLOAD_TO_SERVER;
> + wreq->io_streams[0].prepare_write = ictx->ops->prepare_write;
> + wreq->io_streams[0].issue_write = ictx->ops->issue_write;
> + wreq->io_streams[0].collected_to = start;
> + wreq->io_streams[0].transferred = LONG_MAX;
> +
> + wreq->io_streams[1].stream_nr = 1;
> + wreq->io_streams[1].source = NETFS_WRITE_TO_CACHE;
> + wreq->io_streams[1].collected_to = start;
> + wreq->io_streams[1].transferred = LONG_MAX;
> + if (fscache_resources_valid(&wreq->cache_resources)) {
> + wreq->io_streams[1].avail = true;
> + wreq->io_streams[1].prepare_write = wreq-
> >cache_resources.ops->prepare_write_subreq;
> + wreq->io_streams[1].issue_write = wreq->cache_resources.ops-
> >issue_write;
> + }
> +
> + return wreq;
> +}
> +
> +/**
> + * netfs_prepare_write_failed - Note write preparation failed
> + * @subreq: The subrequest to mark
> + *
> + * Mark a subrequest to note that preparation for write failed.
> + */
> +void netfs_prepare_write_failed(struct netfs_io_subrequest *subreq)
> +{
> + __set_bit(NETFS_SREQ_FAILED, &subreq->flags);
> + trace_netfs_sreq(subreq, netfs_sreq_trace_prep_failed);
> +}
> +EXPORT_SYMBOL(netfs_prepare_write_failed);
> +
> +/*
> + * Prepare a write subrequest. We need to allocate a new subrequest
> + * if we don't have one.
> + */
> +static void netfs_prepare_write(struct netfs_io_request *wreq,
> + struct netfs_io_stream *stream,
> + loff_t start)
> +{
> + struct netfs_io_subrequest *subreq;
> +
> + subreq = netfs_alloc_subrequest(wreq);
> + subreq->source = stream->source;
> + subreq->start = start;
> + subreq->max_len = ULONG_MAX;
> + subreq->max_nr_segs = INT_MAX;
> + subreq->stream_nr = stream->stream_nr;
> +
> + _enter("R=%x[%x]", wreq->debug_id, subreq->debug_index);
> +
> + trace_netfs_sreq_ref(wreq->debug_id, subreq->debug_index,
> + refcount_read(&subreq->ref),
> + netfs_sreq_trace_new);
> +
> + trace_netfs_sreq(subreq, netfs_sreq_trace_prepare);
> +
> + switch (stream->source) {
> + case NETFS_UPLOAD_TO_SERVER:
> + netfs_stat(&netfs_n_wh_upload);
> + subreq->max_len = wreq->wsize;
> + break;
> + case NETFS_WRITE_TO_CACHE:
> + netfs_stat(&netfs_n_wh_write);
> + break;
> + default:
> + WARN_ON_ONCE(1);
> + break;
> + }
> +
> + if (stream->prepare_write)
> + stream->prepare_write(subreq);
> +
> + __set_bit(NETFS_SREQ_IN_PROGRESS, &subreq->flags);
> +
> + /* We add to the end of the list whilst the collector may be walking
> + * the list. The collector only goes nextwards and uses the lock to
> + * remove entries off of the front.
> + */
> + spin_lock(&wreq->lock);
> + list_add_tail(&subreq->rreq_link, &stream->subrequests);
> + if (list_is_first(&subreq->rreq_link, &stream->subrequests)) {
> + stream->front = subreq;
> + if (!stream->active) {
> + stream->collected_to = stream->front->start;
> + /* Write list pointers before active flag */
> + smp_store_release(&stream->active, true);
> + }
> + }
> +
> + spin_unlock(&wreq->lock);
> +
> + stream->construct = subreq;
> +}
> +
> +/*
> + * Set the I/O iterator for the filesystem/cache to use and dispatch the I/O
> + * operation. The operation may be asynchronous and should call
> + * netfs_write_subrequest_terminated() when complete.
> + */
> +static void netfs_do_issue_write(struct netfs_io_stream *stream,
> + struct netfs_io_subrequest *subreq)
> +{
> + struct netfs_io_request *wreq = subreq->rreq;
> +
> + _enter("R=%x[%x],%zx", wreq->debug_id, subreq->debug_index, subreq-
> >len);
> +
> + if (test_bit(NETFS_SREQ_FAILED, &subreq->flags))
> + return netfs_write_subrequest_terminated(subreq, subreq->error,
> false);
> +
> + // TODO: Use encrypted buffer
> + if (test_bit(NETFS_RREQ_USE_IO_ITER, &wreq->flags)) {
> + subreq->io_iter = wreq->io_iter;
> + iov_iter_advance(&subreq->io_iter,
> + subreq->start + subreq->transferred - wreq-
> >start);
> + iov_iter_truncate(&subreq->io_iter,
> + subreq->len - subreq->transferred);
> + } else {
> + iov_iter_xarray(&subreq->io_iter, ITER_SOURCE, &wreq-
> >mapping->i_pages,
> + subreq->start + subreq->transferred,
> + subreq->len - subreq->transferred);
> + }
> +
> + trace_netfs_sreq(subreq, netfs_sreq_trace_submit);
> + stream->issue_write(subreq);
> +}
> +
> +void netfs_reissue_write(struct netfs_io_stream *stream,
> + struct netfs_io_subrequest *subreq)
> +{
> + __set_bit(NETFS_SREQ_IN_PROGRESS, &subreq->flags);
> + netfs_do_issue_write(stream, subreq);
> +}
> +
> +static void netfs_issue_write(struct netfs_io_request *wreq,
> + struct netfs_io_stream *stream)
> +{
> + struct netfs_io_subrequest *subreq = stream->construct;
> +
> + if (!subreq)
> + return;
> + stream->construct = NULL;
> +
> + if (subreq->start + subreq->len > wreq->start + wreq->submitted)
> + wreq->len = wreq->submitted = subreq->start + subreq->len -
> wreq->start;
> + netfs_do_issue_write(stream, subreq);
> +}
> +
> +/*
> + * Add data to the write subrequest, dispatching each as we fill it up or if it
> + * is discontiguous with the previous. We only fill one part at a time so that
> + * we can avoid overrunning the credits obtained (cifs) and try to parallelise
> + * content-crypto preparation with network writes.
> + */
> +int netfs_advance_write(struct netfs_io_request *wreq,
> + struct netfs_io_stream *stream,
> + loff_t start, size_t len, bool to_eof)
> +{
> + struct netfs_io_subrequest *subreq = stream->construct;
> + size_t part;
> +
> + if (!stream->avail) {
> + _leave("no write");
> + return len;
> + }
> +
> + _enter("R=%x[%x]", wreq->debug_id, subreq ? subreq->debug_index : 0);
> +
> + if (subreq && start != subreq->start + subreq->len) {
> + netfs_issue_write(wreq, stream);
> + subreq = NULL;
> + }
> +
> + if (!stream->construct)
> + netfs_prepare_write(wreq, stream, start);
> + subreq = stream->construct;
> +
> + part = min(subreq->max_len - subreq->len, len);
> + _debug("part %zx/%zx %zx/%zx", subreq->len, subreq->max_len, part,
> len);
> + subreq->len += part;
> + subreq->nr_segs++;
> +
> + if (subreq->len >= subreq->max_len ||
> + subreq->nr_segs >= subreq->max_nr_segs ||
> + to_eof) {
> + netfs_issue_write(wreq, stream);
> + subreq = NULL;
> + }
> +
> + return part;
> +}
> +
> +/*
> + * Write some of a pending folio data back to the server.
> + */
> +static int netfs_write_folio(struct netfs_io_request *wreq,
> + struct writeback_control *wbc,
> + 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;
> + struct netfs_group *fgroup; /* TODO: Use this with ceph */
> + struct netfs_folio *finfo;
> + size_t fsize = folio_size(folio), flen = fsize, foff = 0;
> + loff_t fpos = folio_pos(folio);
> + bool to_eof = false, streamw = false;
> + bool debug = false;
> +
> + _enter("");
> +
> + if (fpos >= wreq->i_size) {
> + /* mmap beyond eof. */
> + _debug("beyond eof");
> + folio_start_writeback(folio);
> + folio_unlock(folio);
> + wreq->nr_group_rel += netfs_folio_written_back(folio);
> + netfs_put_group_many(wreq->group, wreq->nr_group_rel);
> + wreq->nr_group_rel = 0;
> + return 0;
> + }
> +
> + fgroup = netfs_folio_group(folio);
> + finfo = netfs_folio_info(folio);
> + if (finfo) {
> + foff = finfo->dirty_offset;
> + flen = foff + finfo->dirty_len;
> + streamw = true;
> + }
> +
> + if (wreq->origin == NETFS_WRITETHROUGH) {
> + to_eof = false;
> + if (flen > wreq->i_size - fpos)
> + flen = wreq->i_size - fpos;
> + } else if (flen > wreq->i_size - fpos) {
> + flen = wreq->i_size - fpos;
> + if (!streamw)
> + folio_zero_segment(folio, flen, fsize);
> + to_eof = true;
> + } else if (flen == wreq->i_size - fpos) {
> + to_eof = true;
> + }
> + flen -= foff;
> +
> + _debug("folio %zx %zx %zx", foff, flen, fsize);
> +
> + /* Deal with discontinuities in the stream of dirty pages. These can
> + * arise from a number of sources:
> + *
> + * (1) Intervening non-dirty pages from random-access writes, multiple
> + * flushers writing back different parts simultaneously and manual
> + * syncing.
> + *
> + * (2) Partially-written pages from write-streaming.
> + *
> + * (3) Pages that belong to a different write-back group (eg. Ceph
> + * snapshots).
> + *
> + * (4) Actually-clean pages that were marked for write to the cache
> + * when they were read. Note that these appear as a special
> + * write-back group.
> + */
> + if (fgroup == NETFS_FOLIO_COPY_TO_CACHE) {
> + netfs_issue_write(wreq, upload);
> + } else if (fgroup != wreq->group) {
> + /* We can't write this page to the server yet. */
> + kdebug("wrong group");
> + folio_redirty_for_writepage(wbc, folio);
> + folio_unlock(folio);
> + netfs_issue_write(wreq, upload);
> + netfs_issue_write(wreq, cache);
> + return 0;
> + }
> +
> + if (foff > 0)
> + netfs_issue_write(wreq, upload);
> + if (streamw)
> + netfs_issue_write(wreq, cache);
> +
> + /* Flip the page to the writeback state and unlock. If we're called
> + * from write-through, then the page has already been put into the wb
> + * state.
> + */
> + if (wreq->origin == NETFS_WRITEBACK)
> + folio_start_writeback(folio);
> + folio_unlock(folio);
> +
> + if (fgroup == NETFS_FOLIO_COPY_TO_CACHE) {
> + if (!fscache_resources_valid(&wreq->cache_resources)) {
> + trace_netfs_folio(folio, netfs_folio_trace_cancel_copy);
> + netfs_issue_write(wreq, upload);
> + netfs_folio_written_back(folio);
> + return 0;
> + }
> + trace_netfs_folio(folio, netfs_folio_trace_store_copy);
> + } else if (!upload->construct) {
> + trace_netfs_folio(folio, netfs_folio_trace_store);
> + } else {
> + trace_netfs_folio(folio, netfs_folio_trace_store_plus);
> + }
> +
> + /* 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_max_len = fsize;
> + stream->submit_off = foff;
> + stream->submit_len = flen;
> + if ((stream->source == NETFS_WRITE_TO_CACHE && streamw)
> ||
> + (stream->source == NETFS_UPLOAD_TO_SERVER &&
> + fgroup == NETFS_FOLIO_COPY_TO_CACHE)) {
> + stream->submit_off = UINT_MAX;
> + stream->submit_len = 0;
> + stream->submit_max_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];
> +
> + part = netfs_advance_write(wreq, stream, fpos + stream-
> >submit_off,
> + stream->submit_len, to_eof);
> + atomic64_set(&wreq->issued_to, fpos + stream->submit_off);
> + stream->submit_off += part;
> + stream->submit_max_len -= part;
> + if (part > stream->submit_len)
> + stream->submit_len = 0;
> + else
> + stream->submit_len -= part;
> + if (part > 0)
> + debug = true;
> + }
> +
> + atomic64_set(&wreq->issued_to, fpos + fsize);
> +
> + if (!debug)
> + kdebug("R=%x: No submit", wreq->debug_id);
> +
> + if (flen < fsize)
> + for (int s = 0; s < NR_IO_STREAMS; s++)
> + netfs_issue_write(wreq, &wreq->io_streams[s]);
> +
> + _leave(" = 0");
> + return 0;
> +}
> +
> +/*
> + * Write some of the pending data back to the server
> + */
> +int new_netfs_writepages(struct address_space *mapping,
> + struct writeback_control *wbc)
> +{
> + struct netfs_inode *ictx = netfs_inode(mapping->host);
> + struct netfs_io_request *wreq = NULL;
> + struct folio *folio;
> + int error = 0;
> +
> + if (wbc->sync_mode == WB_SYNC_ALL)
> + mutex_lock(&ictx->wb_lock);
> + else if (!mutex_trylock(&ictx->wb_lock))
> + return 0;
> +
> + /* Need the first folio to be able to set up the op. */
> + folio = writeback_iter(mapping, wbc, NULL, &error);
> + if (!folio)
> + goto out;
> +
> + wreq = netfs_create_write_req(mapping, NULL, folio_pos(folio),
> NETFS_WRITEBACK);
> + if (IS_ERR(wreq)) {
> + error = PTR_ERR(wreq);
> + goto couldnt_start;
> + }
> +
> + trace_netfs_write(wreq, netfs_write_trace_writeback);
> + netfs_stat(&netfs_n_wh_writepages);
> +
> + do {
> + _debug("wbiter %lx %llx", folio->index, wreq->start + wreq-
> >submitted);
> +
> + /* It appears we don't have to handle cyclic writeback wrapping. */
> + WARN_ON_ONCE(wreq && folio_pos(folio) < wreq->start + wreq-
> >submitted);
> +
> + if (netfs_folio_group(folio) != NETFS_FOLIO_COPY_TO_CACHE
> &&
> + unlikely(!test_bit(NETFS_RREQ_UPLOAD_TO_SERVER,
> &wreq->flags))) {
> + set_bit(NETFS_RREQ_UPLOAD_TO_SERVER, &wreq-
> >flags);
> + wreq->netfs_ops->begin_writeback(wreq);
> + }
> +
> + error = netfs_write_folio(wreq, wbc, folio);
> + if (error < 0)
> + break;
> + } while ((folio = writeback_iter(mapping, wbc, folio, &error)));
> +
> + 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", error);
> + return error;
> +
> +couldnt_start:
> + netfs_kill_dirty_pages(mapping, wbc, folio);
> +out:
> + mutex_unlock(&ictx->wb_lock);
> + _leave(" = %d", error);
> + return error;
> +}
> +EXPORT_SYMBOL(new_netfs_writepages);
> +
> +/*
> + * Begin a write operation for writing through the pagecache.
> + */
> +struct netfs_io_request *new_netfs_begin_writethrough(struct kiocb *iocb, size_t
> len)
> +{
> + struct netfs_io_request *wreq = NULL;
> + struct netfs_inode *ictx = netfs_inode(file_inode(iocb->ki_filp));
> +
> + mutex_lock(&ictx->wb_lock);
> +
> + wreq = netfs_create_write_req(iocb->ki_filp->f_mapping, iocb->ki_filp,
> + iocb->ki_pos, NETFS_WRITETHROUGH);
> + if (IS_ERR(wreq))
> + mutex_unlock(&ictx->wb_lock);
> +
> + wreq->io_streams[0].avail = true;
> + trace_netfs_write(wreq, netfs_write_trace_writethrough);

Missing mutex_unlock() before return.

Thanks,
Naveen

> + return wreq;
> +}
> +
> +/*
> + * Advance the state of the write operation used when writing through the
> + * pagecache. Data has been copied into the pagecache that we need to append
> + * to the request. If we've added more than wsize then we need to create a new
> + * subrequest.
> + */
> +int new_netfs_advance_writethrough(struct netfs_io_request *wreq, struct
> writeback_control *wbc,
> + struct folio *folio, size_t copied, bool
> to_page_end,
> + struct folio **writethrough_cache)
> +{
> + _enter("R=%x ic=%zu ws=%u cp=%zu tp=%u",
> + wreq->debug_id, wreq->iter.count, wreq->wsize, copied,
> to_page_end);
> +
> + if (!*writethrough_cache) {
> + if (folio_test_dirty(folio))
> + /* Sigh. mmap. */
> + folio_clear_dirty_for_io(folio);
> +
> + /* We can make multiple writes to the folio... */
> + folio_start_writeback(folio);
> + if (wreq->len == 0)
> + trace_netfs_folio(folio, netfs_folio_trace_wthru);
> + else
> + trace_netfs_folio(folio, netfs_folio_trace_wthru_plus);
> + *writethrough_cache = folio;
> + }
> +
> + wreq->len += copied;
> + if (!to_page_end)
> + return 0;
> +
> + *writethrough_cache = NULL;
> + return netfs_write_folio(wreq, wbc, folio);
> +}
> +
> +/*
> + * End a write operation used when writing through the pagecache.
> + */
> +int new_netfs_end_writethrough(struct netfs_io_request *wreq, struct
> writeback_control *wbc,
> + struct folio *writethrough_cache)
> +{
> + struct netfs_inode *ictx = netfs_inode(wreq->inode);
> + int ret;
> +
> + _enter("R=%x", wreq->debug_id);
> +
> + if (writethrough_cache)
> + netfs_write_folio(wreq, wbc, writethrough_cache);
> +
> + netfs_issue_write(wreq, &wreq->io_streams[0]);
> + netfs_issue_write(wreq, &wreq->io_streams[1]);
> + smp_wmb(); /* Write lists before ALL_QUEUED. */
> + set_bit(NETFS_RREQ_ALL_QUEUED, &wreq->flags);
> +
> + mutex_unlock(&ictx->wb_lock);
> +
> + ret = wreq->error;
> + netfs_put_request(wreq, false, netfs_rreq_trace_put_return);
> + return ret;
> +}
> +
> +/*
> + * Write data to the server without going through the pagecache and without
> + * writing it to the local cache.
> + */
> +int netfs_unbuffered_write(struct netfs_io_request *wreq, bool may_wait, size_t
> len)
> +{
> + struct netfs_io_stream *upload = &wreq->io_streams[0];
> + ssize_t part;
> + loff_t start = wreq->start;
> + int error = 0;
> +
> + _enter("%zx", len);
> +
> + if (wreq->origin == NETFS_DIO_WRITE)
> + inode_dio_begin(wreq->inode);
> +
> + while (len) {
> + // TODO: Prepare content encryption
> +
> + _debug("unbuffered %zx", len);
> + part = netfs_advance_write(wreq, upload, start, len, false);
> + start += part;
> + len -= part;
> + if (test_bit(NETFS_RREQ_PAUSE, &wreq->flags)) {
> + trace_netfs_rreq(wreq, netfs_rreq_trace_wait_pause);
> + wait_on_bit(&wreq->flags, NETFS_RREQ_PAUSE,
> TASK_UNINTERRUPTIBLE);
> + }
> + if (test_bit(NETFS_RREQ_FAILED, &wreq->flags))
> + break;
> + }
> +
> + netfs_issue_write(wreq, upload);
> +
> + smp_wmb(); /* Write lists before ALL_QUEUED. */
> + set_bit(NETFS_RREQ_ALL_QUEUED, &wreq->flags);
> + if (list_empty(&upload->subrequests))
> + netfs_wake_write_collector(wreq, false);
> +
> + _leave(" = %d", error);
> + return error;
> +}
> diff --git a/include/linux/netfs.h b/include/linux/netfs.h
> index 88269681d4fc..42dba05a428b 100644
> --- a/include/linux/netfs.h
> +++ b/include/linux/netfs.h
> @@ -64,6 +64,7 @@ struct netfs_inode {
> #if IS_ENABLED(CONFIG_FSCACHE)
> struct fscache_cookie *cache;
> #endif
> + struct mutex wb_lock; /* Writeback serialisation */
> loff_t remote_i_size; /* Size of the remote file */
> loff_t zero_point; /* Size after which we assume
> there's no data
> * on the server */
> @@ -71,7 +72,6 @@ struct netfs_inode {
> #define NETFS_ICTX_ODIRECT 0 /* The file has DIO in
> progress */
> #define NETFS_ICTX_UNBUFFERED 1 /* I/O should not use the
> pagecache */
> #define NETFS_ICTX_WRITETHROUGH 2 /* Write-through
> caching */
> -#define NETFS_ICTX_NO_WRITE_STREAMING 3 /* Don't engage in
> write-streaming */
> #define NETFS_ICTX_USE_PGPRIV2 31 /* [DEPRECATED] Use
> PG_private_2 to mark
> * write to cache on read */
> };
> @@ -126,6 +126,33 @@ static inline struct netfs_group *netfs_folio_group(struct
> folio *folio)
> return priv;
> }
>
> +/*
> + * Stream of I/O subrequests going to a particular destination, such as the
> + * server or the local cache. This is mainly intended for writing where we may
> + * have to write to multiple destinations concurrently.
> + */
> +struct netfs_io_stream {
> + /* Submission tracking */
> + struct netfs_io_subrequest *construct; /* Op being constructed */
> + unsigned int submit_off; /* Folio offset we're submitting
> from */
> + unsigned int submit_len; /* Amount of data left to submit */
> + unsigned int submit_max_len; /* Amount I/O can be
> rounded up to */
> + void (*prepare_write)(struct netfs_io_subrequest *subreq);
> + void (*issue_write)(struct netfs_io_subrequest *subreq);
> + /* Collection tracking */
> + struct list_head subrequests; /* Contributory I/O operations */
> + struct netfs_io_subrequest *front; /* Op being collected */
> + unsigned long long collected_to; /* Position we've collected results
> to */
> + size_t transferred; /* The amount transferred from
> this stream */
> + enum netfs_io_source source; /* Where to read from/write to */
> + unsigned short error; /* Aggregate error for the stream
> */
> + unsigned char stream_nr; /* Index of stream in parent table
> */
> + bool avail; /* T if stream is available */
> + bool active; /* T if stream is active */
> + bool need_retry; /* T if this stream needs retrying
> */
> + bool failed; /* T if this stream failed */
> +};
> +
> /*
> * Resources required to do operations on a cache.
> */
> @@ -150,13 +177,16 @@ struct netfs_io_subrequest {
> struct list_head rreq_link; /* Link in rreq->subrequests */
> struct iov_iter io_iter; /* Iterator for this subrequest */
> unsigned long long start; /* Where to start the I/O */
> + size_t max_len; /* Maximum size of the I/O */
> size_t len; /* Size of the I/O */
> size_t transferred; /* Amount of data transferred */
> refcount_t ref;
> short error; /* 0 or error that occurred */
> unsigned short debug_index; /* Index in list (for debugging
> output) */
> + unsigned int nr_segs; /* Number of segs in io_iter */
> unsigned int max_nr_segs; /* 0 or max number of segments
> in an iterator */
> enum netfs_io_source source; /* Where to read from/write to */
> + unsigned char stream_nr; /* I/O stream this belongs to */
> unsigned long flags;
> #define NETFS_SREQ_COPY_TO_CACHE 0 /* Set if should copy the
> data to the cache */
> #define NETFS_SREQ_CLEAR_TAIL 1 /* Set if the rest of the
> read should be cleared */
> @@ -164,6 +194,11 @@ struct netfs_io_subrequest {
> #define NETFS_SREQ_SEEK_DATA_READ 3 /* Set if ->read() should
> SEEK_DATA first */
> #define NETFS_SREQ_NO_PROGRESS 4 /* Set if we didn't
> manage to read any data */
> #define NETFS_SREQ_ONDEMAND 5 /* Set if it's from on-
> demand read mode */
> +#define NETFS_SREQ_BOUNDARY 6 /* Set if ends on hard
> boundary (eg. ceph object) */
> +#define NETFS_SREQ_IN_PROGRESS 8 /* Unlocked when
> the subrequest completes */
> +#define NETFS_SREQ_NEED_RETRY 9 /* Set if the
> filesystem requests a retry */
> +#define NETFS_SREQ_RETRYING 10 /* Set if we're retrying */
> +#define NETFS_SREQ_FAILED 11 /* Set if the subreq failed
> unretryably */
> };
>
> enum netfs_io_origin {
> @@ -194,6 +229,9 @@ struct netfs_io_request {
> struct netfs_cache_resources cache_resources;
> struct list_head proc_link; /* Link in netfs_iorequests */
> struct list_head subrequests; /* Contributory I/O operations */
> + struct netfs_io_stream io_streams[2]; /* Streams of parallel I/O
> operations */
> +#define NR_IO_STREAMS 2 //wreq->nr_io_streams
> + struct netfs_group *group; /* Writeback group being written
> back */
> struct iov_iter iter; /* Unencrypted-side iterator */
> struct iov_iter io_iter; /* I/O (Encrypted-side) iterator */
> void *netfs_priv; /* Private data for the netfs */
> @@ -203,6 +241,8 @@ struct netfs_io_request {
> unsigned int rsize; /* Maximum read size (0 for none)
> */
> unsigned int wsize; /* Maximum write size (0 for
> none) */
> atomic_t subreq_counter; /* Next subreq-
> >debug_index */
> + unsigned int nr_group_rel; /* Number of refs to release on -
> >group */
> + spinlock_t lock; /* Lock for queuing subreqs */
> atomic_t nr_outstanding; /* Number of ops in progress */
> atomic_t nr_copy_ops; /* Number of copy-to-cache ops in
> progress */
> size_t upper_len; /* Length can be extended to here
> */
> @@ -214,6 +254,10 @@ struct netfs_io_request {
> bool direct_bv_unpin; /* T if direct_bv[] must be
> unpinned */
> unsigned long long i_size; /* Size of the file */
> unsigned long long start; /* Start position */
> + atomic64_t issued_to; /* Write issuer folio cursor */
> + unsigned long long contiguity; /* Tracking for gaps in the
> writeback sequence */
> + unsigned long long collected_to; /* Point we've collected to */
> + unsigned long long cleaned_to; /* Position we've cleaned folios to
> */
> pgoff_t no_unlock_folio; /* Don't unlock this folio after
> read */
> refcount_t ref;
> unsigned long flags;
> @@ -227,6 +271,9 @@ struct netfs_io_request {
> #define NETFS_RREQ_UPLOAD_TO_SERVER 8 /* Need to write to
> the server */
> #define NETFS_RREQ_NONBLOCK 9 /* Don't block if possible
> (O_NONBLOCK) */
> #define NETFS_RREQ_BLOCKED 10 /* We blocked */
> +#define NETFS_RREQ_PAUSE 11 /* Pause subrequest
> generation */
> +#define NETFS_RREQ_USE_IO_ITER 12 /* Use ->io_iter
> rather than ->i_pages */
> +#define NETFS_RREQ_ALL_QUEUED 13 /* All subreqs are
> now queued */
> #define NETFS_RREQ_USE_PGPRIV2 31 /*
> [DEPRECATED] Use PG_private_2 to mark
> * write to cache on read */
> const struct netfs_request_ops *netfs_ops;
> @@ -258,6 +305,9 @@ struct netfs_request_ops {
> /* Write request handling */
> void (*create_write_requests)(struct netfs_io_request *wreq,
> loff_t start, size_t len);
> + void (*begin_writeback)(struct netfs_io_request *wreq);
> + void (*prepare_write)(struct netfs_io_subrequest *subreq);
> + void (*issue_write)(struct netfs_io_subrequest *subreq);
> void (*invalidate_cache)(struct netfs_io_request *wreq);
> };
>
> @@ -292,6 +342,9 @@ struct netfs_cache_ops {
> netfs_io_terminated_t term_func,
> void *term_func_priv);
>
> + /* Write data to the cache from a netfs subrequest. */
> + void (*issue_write)(struct netfs_io_subrequest *subreq);
> +
> /* Expand readahead request */
> void (*expand_readahead)(struct netfs_cache_resources *cres,
> unsigned long long *_start,
> @@ -304,6 +357,13 @@ struct netfs_cache_ops {
> enum netfs_io_source (*prepare_read)(struct netfs_io_subrequest
> *subreq,
> unsigned long long i_size);
>
> + /* Prepare a write subrequest, working out if we're allowed to do it
> + * and finding out the maximum amount of data to gather before
> + * attempting to submit. If we're not permitted to do it, the
> + * subrequest should be marked failed.
> + */
> + void (*prepare_write_subreq)(struct netfs_io_subrequest *subreq);
> +
> /* Prepare a write operation, working out what part of the write we can
> * actually do.
> */
> @@ -349,6 +409,8 @@ int netfs_write_begin(struct netfs_inode *, struct file *,
> struct folio **, void **fsdata);
> int netfs_writepages(struct address_space *mapping,
> struct writeback_control *wbc);
> +int new_netfs_writepages(struct address_space *mapping,
> + struct writeback_control *wbc);
> bool netfs_dirty_folio(struct address_space *mapping, struct folio *folio);
> int netfs_unpin_writeback(struct inode *inode, struct writeback_control *wbc);
> void netfs_clear_inode_writeback(struct inode *inode, const void *aux);
> @@ -372,8 +434,11 @@ size_t netfs_limit_iter(const struct iov_iter *iter, size_t
> start_offset,
> struct netfs_io_subrequest *netfs_create_write_request(
> struct netfs_io_request *wreq, enum netfs_io_source dest,
> loff_t start, size_t len, work_func_t worker);
> +void netfs_prepare_write_failed(struct netfs_io_subrequest *subreq);
> void netfs_write_subrequest_terminated(void *_op, ssize_t transferred_or_error,
> bool was_async);
> +void new_netfs_write_subrequest_terminated(void *_op, ssize_t
> transferred_or_error,
> + bool was_async);
> void netfs_queue_write_request(struct netfs_io_subrequest *subreq);
>
> int netfs_start_io_read(struct inode *inode);
> @@ -415,6 +480,7 @@ static inline void netfs_inode_init(struct netfs_inode *ctx,
> #if IS_ENABLED(CONFIG_FSCACHE)
> ctx->cache = NULL;
> #endif
> + mutex_init(&ctx->wb_lock);
> /* ->releasepage() drives zero_point */
> if (use_zero_point) {
> ctx->zero_point = ctx->remote_i_size;
> diff --git a/include/trace/events/netfs.h b/include/trace/events/netfs.h
> index 7126d2ea459c..e7700172ae7e 100644
> --- a/include/trace/events/netfs.h
> +++ b/include/trace/events/netfs.h
> @@ -44,14 +44,18 @@
> #define netfs_rreq_traces \
> EM(netfs_rreq_trace_assess, "ASSESS ") \
> EM(netfs_rreq_trace_copy, "COPY ") \
> + EM(netfs_rreq_trace_collect, "COLLECT") \
> EM(netfs_rreq_trace_done, "DONE ") \
> EM(netfs_rreq_trace_free, "FREE ") \
> EM(netfs_rreq_trace_redirty, "REDIRTY") \
> EM(netfs_rreq_trace_resubmit, "RESUBMT") \
> + EM(netfs_rreq_trace_set_pause, "PAUSE ") \
> EM(netfs_rreq_trace_unlock, "UNLOCK ") \
> EM(netfs_rreq_trace_unmark, "UNMARK ") \
> EM(netfs_rreq_trace_wait_ip, "WAIT-IP") \
> + EM(netfs_rreq_trace_wait_pause, "WT-PAUS") \
> EM(netfs_rreq_trace_wake_ip, "WAKE-IP") \
> + EM(netfs_rreq_trace_unpause, "UNPAUSE") \
> E_(netfs_rreq_trace_write_done, "WR-DONE")
>
> #define netfs_sreq_sources \
> @@ -64,11 +68,15 @@
> E_(NETFS_INVALID_WRITE, "INVL")
>
> #define netfs_sreq_traces \
> + EM(netfs_sreq_trace_discard, "DSCRD") \
> EM(netfs_sreq_trace_download_instead, "RDOWN") \
> + EM(netfs_sreq_trace_fail, "FAIL ") \
> EM(netfs_sreq_trace_free, "FREE ") \
> EM(netfs_sreq_trace_limited, "LIMIT") \
> EM(netfs_sreq_trace_prepare, "PREP ") \
> + EM(netfs_sreq_trace_prep_failed, "PRPFL") \
> EM(netfs_sreq_trace_resubmit_short, "SHORT") \
> + EM(netfs_sreq_trace_retry, "RETRY") \
> EM(netfs_sreq_trace_submit, "SUBMT") \
> EM(netfs_sreq_trace_terminated, "TERM ") \
> EM(netfs_sreq_trace_write, "WRITE") \
> @@ -88,6 +96,7 @@
> #define netfs_rreq_ref_traces \
> EM(netfs_rreq_trace_get_for_outstanding,"GET OUTSTND") \
> EM(netfs_rreq_trace_get_subreq, "GET SUBREQ ") \
> + EM(netfs_rreq_trace_get_work, "GET WORK ") \
> EM(netfs_rreq_trace_put_complete, "PUT COMPLT ") \
> EM(netfs_rreq_trace_put_discard, "PUT DISCARD") \
> EM(netfs_rreq_trace_put_failed, "PUT FAILED ") \
> @@ -95,6 +104,8 @@
> EM(netfs_rreq_trace_put_return, "PUT RETURN ") \
> EM(netfs_rreq_trace_put_subreq, "PUT SUBREQ ") \
> EM(netfs_rreq_trace_put_work, "PUT WORK ") \
> + EM(netfs_rreq_trace_put_work_complete, "PUT WORK CP") \
> + EM(netfs_rreq_trace_put_work_nq, "PUT WORK NQ") \
> EM(netfs_rreq_trace_see_work, "SEE WORK ") \
> E_(netfs_rreq_trace_new, "NEW ")
>
> @@ -103,11 +114,14 @@
> EM(netfs_sreq_trace_get_resubmit, "GET RESUBMIT") \
> EM(netfs_sreq_trace_get_short_read, "GET SHORTRD") \
> EM(netfs_sreq_trace_new, "NEW ") \
> + EM(netfs_sreq_trace_put_cancel, "PUT CANCEL ") \
> EM(netfs_sreq_trace_put_clear, "PUT CLEAR ") \
> EM(netfs_sreq_trace_put_discard, "PUT DISCARD") \
> + EM(netfs_sreq_trace_put_done, "PUT DONE ") \
> EM(netfs_sreq_trace_put_failed, "PUT FAILED ") \
> EM(netfs_sreq_trace_put_merged, "PUT MERGED ") \
> EM(netfs_sreq_trace_put_no_copy, "PUT NO COPY") \
> + EM(netfs_sreq_trace_put_oom, "PUT OOM ") \
> EM(netfs_sreq_trace_put_wip, "PUT WIP ") \
> EM(netfs_sreq_trace_put_work, "PUT WORK ") \
> E_(netfs_sreq_trace_put_terminated, "PUT TERM ")
> @@ -124,7 +138,9 @@
> EM(netfs_streaming_filled_page, "mod-streamw-f") \
> EM(netfs_streaming_cont_filled_page, "mod-streamw-f+") \
> /* The rest are for writeback */ \
> + EM(netfs_folio_trace_cancel_copy, "cancel-copy") \
> EM(netfs_folio_trace_clear, "clear") \
> + EM(netfs_folio_trace_clear_cc, "clear-cc") \
> EM(netfs_folio_trace_clear_s, "clear-s") \
> EM(netfs_folio_trace_clear_g, "clear-g") \
> EM(netfs_folio_trace_copy, "copy") \
> @@ -133,16 +149,26 @@
> EM(netfs_folio_trace_end_copy, "end-copy") \
> EM(netfs_folio_trace_filled_gaps, "filled-gaps") \
> EM(netfs_folio_trace_kill, "kill") \
> + EM(netfs_folio_trace_kill_cc, "kill-cc") \
> + EM(netfs_folio_trace_kill_g, "kill-g") \
> + EM(netfs_folio_trace_kill_s, "kill-s") \
> EM(netfs_folio_trace_mkwrite, "mkwrite") \
> EM(netfs_folio_trace_mkwrite_plus, "mkwrite+") \
> + EM(netfs_folio_trace_not_under_wback, "!wback") \
> EM(netfs_folio_trace_read_gaps, "read-gaps") \
> EM(netfs_folio_trace_redirty, "redirty") \
> EM(netfs_folio_trace_redirtied, "redirtied") \
> EM(netfs_folio_trace_store, "store") \
> + EM(netfs_folio_trace_store_copy, "store-copy") \
> EM(netfs_folio_trace_store_plus, "store+") \
> EM(netfs_folio_trace_wthru, "wthru") \
> E_(netfs_folio_trace_wthru_plus, "wthru+")
>
> +#define netfs_collect_contig_traces \
> + EM(netfs_contig_trace_collect, "Collect") \
> + EM(netfs_contig_trace_jump, "-->JUMP-->") \
> + E_(netfs_contig_trace_unlock, "Unlock")
> +
> #ifndef __NETFS_DECLARE_TRACE_ENUMS_ONCE_ONLY
> #define __NETFS_DECLARE_TRACE_ENUMS_ONCE_ONLY
>
> @@ -159,6 +185,7 @@ enum netfs_failure { netfs_failures } __mode(byte);
> enum netfs_rreq_ref_trace { netfs_rreq_ref_traces } __mode(byte);
> enum netfs_sreq_ref_trace { netfs_sreq_ref_traces } __mode(byte);
> enum netfs_folio_trace { netfs_folio_traces } __mode(byte);
> +enum netfs_collect_contig_trace { netfs_collect_contig_traces } __mode(byte);
>
> #endif
>
> @@ -180,6 +207,7 @@ netfs_failures;
> netfs_rreq_ref_traces;
> netfs_sreq_ref_traces;
> netfs_folio_traces;
> +netfs_collect_contig_traces;
>
> /*
> * Now redefine the EM() and E_() macros to map the enums to the strings that
> @@ -413,16 +441,18 @@ TRACE_EVENT(netfs_write_iter,
> __field(unsigned long long, start )
> __field(size_t, len )
> __field(unsigned int, flags )
> + __field(unsigned int, ino )
> ),
>
> TP_fast_assign(
> __entry->start = iocb->ki_pos;
> __entry->len = iov_iter_count(from);
> + __entry->ino = iocb->ki_filp->f_inode->i_ino;
> __entry->flags = iocb->ki_flags;
> ),
>
> - TP_printk("WRITE-ITER s=%llx l=%zx f=%x",
> - __entry->start, __entry->len, __entry->flags)
> + TP_printk("WRITE-ITER i=%x s=%llx l=%zx f=%x",
> + __entry->ino, __entry->start, __entry->len, __entry->flags)
> );
>
> TRACE_EVENT(netfs_write,
> @@ -434,6 +464,7 @@ TRACE_EVENT(netfs_write,
> TP_STRUCT__entry(
> __field(unsigned int, wreq )
> __field(unsigned int, cookie )
> + __field(unsigned int, ino )
> __field(enum netfs_write_trace, what )
> __field(unsigned long long, start )
> __field(unsigned long long, len )
> @@ -444,18 +475,213 @@ TRACE_EVENT(netfs_write,
> struct fscache_cookie *__cookie = netfs_i_cookie(__ctx);
> __entry->wreq = wreq->debug_id;
> __entry->cookie = __cookie ? __cookie->debug_id : 0;
> + __entry->ino = wreq->inode->i_ino;
> __entry->what = what;
> __entry->start = wreq->start;
> __entry->len = wreq->len;
> ),
>
> - TP_printk("R=%08x %s c=%08x by=%llx-%llx",
> + TP_printk("R=%08x %s c=%08x i=%x by=%llx-%llx",
> __entry->wreq,
> __print_symbolic(__entry->what, netfs_write_traces),
> __entry->cookie,
> + __entry->ino,
> __entry->start, __entry->start + __entry->len - 1)
> );
>
> +TRACE_EVENT(netfs_collect,
> + TP_PROTO(const struct netfs_io_request *wreq),
> +
> + TP_ARGS(wreq),
> +
> + TP_STRUCT__entry(
> + __field(unsigned int, wreq )
> + __field(unsigned int, len )
> + __field(unsigned long long, transferred )
> + __field(unsigned long long, start )
> + ),
> +
> + TP_fast_assign(
> + __entry->wreq = wreq->debug_id;
> + __entry->start = wreq->start;
> + __entry->len = wreq->len;
> + __entry->transferred = wreq->transferred;
> + ),
> +
> + TP_printk("R=%08x s=%llx-%llx",
> + __entry->wreq,
> + __entry->start + __entry->transferred,
> + __entry->start + __entry->len)
> + );
> +
> +TRACE_EVENT(netfs_collect_contig,
> + TP_PROTO(const struct netfs_io_request *wreq, unsigned long long
> to,
> + enum netfs_collect_contig_trace type),
> +
> + TP_ARGS(wreq, to, type),
> +
> + TP_STRUCT__entry(
> + __field(unsigned int, wreq)
> + __field(enum netfs_collect_contig_trace, type)
> + __field(unsigned long long, contiguity)
> + __field(unsigned long long, to)
> + ),
> +
> + TP_fast_assign(
> + __entry->wreq = wreq->debug_id;
> + __entry->type = type;
> + __entry->contiguity = wreq->contiguity;
> + __entry->to = to;
> + ),
> +
> + TP_printk("R=%08x %llx -> %llx %s",
> + __entry->wreq,
> + __entry->contiguity,
> + __entry->to,
> + __print_symbolic(__entry->type, netfs_collect_contig_traces))
> + );
> +
> +TRACE_EVENT(netfs_collect_sreq,
> + TP_PROTO(const struct netfs_io_request *wreq,
> + const struct netfs_io_subrequest *subreq),
> +
> + TP_ARGS(wreq, subreq),
> +
> + TP_STRUCT__entry(
> + __field(unsigned int, wreq )
> + __field(unsigned int, subreq )
> + __field(unsigned int, stream )
> + __field(unsigned int, len )
> + __field(unsigned int, transferred )
> + __field(unsigned long long, start )
> + ),
> +
> + TP_fast_assign(
> + __entry->wreq = wreq->debug_id;
> + __entry->subreq = subreq->debug_index;
> + __entry->stream = subreq->stream_nr;
> + __entry->start = subreq->start;
> + __entry->len = subreq->len;
> + __entry->transferred = subreq->transferred;
> + ),
> +
> + TP_printk("R=%08x[%u:%02x] s=%llx t=%x/%x",
> + __entry->wreq, __entry->stream, __entry->subreq,
> + __entry->start, __entry->transferred, __entry->len)
> + );
> +
> +TRACE_EVENT(netfs_collect_folio,
> + TP_PROTO(const struct netfs_io_request *wreq,
> + const struct folio *folio,
> + unsigned long long fend,
> + unsigned long long collected_to),
> +
> + TP_ARGS(wreq, folio, fend, collected_to),
> +
> + TP_STRUCT__entry(
> + __field(unsigned int, wreq )
> + __field(unsigned long, index )
> + __field(unsigned long long, fend )
> + __field(unsigned long long, cleaned_to )
> + __field(unsigned long long, collected_to )
> + ),
> +
> + TP_fast_assign(
> + __entry->wreq = wreq->debug_id;
> + __entry->index = folio->index;
> + __entry->fend = fend;
> + __entry->cleaned_to = wreq->cleaned_to;
> + __entry->collected_to = collected_to;
> + ),
> +
> + TP_printk("R=%08x ix=%05lx r=%llx-%llx t=%llx/%llx",
> + __entry->wreq, __entry->index,
> + (unsigned long long)__entry->index * PAGE_SIZE, __entry-
> >fend,
> + __entry->cleaned_to, __entry->collected_to)
> + );
> +
> +TRACE_EVENT(netfs_collect_state,
> + TP_PROTO(const struct netfs_io_request *wreq,
> + unsigned long long collected_to,
> + unsigned int notes),
> +
> + TP_ARGS(wreq, collected_to, notes),
> +
> + TP_STRUCT__entry(
> + __field(unsigned int, wreq )
> + __field(unsigned int, notes )
> + __field(unsigned long long, collected_to )
> + __field(unsigned long long, cleaned_to )
> + __field(unsigned long long, contiguity )
> + ),
> +
> + TP_fast_assign(
> + __entry->wreq = wreq->debug_id;
> + __entry->notes = notes;
> + __entry->collected_to = collected_to;
> + __entry->cleaned_to = wreq->cleaned_to;
> + __entry->contiguity = wreq->contiguity;
> + ),
> +
> + TP_printk("R=%08x cto=%llx fto=%llx ctg=%llx n=%x",
> + __entry->wreq, __entry->collected_to,
> + __entry->cleaned_to, __entry->contiguity,
> + __entry->notes)
> + );
> +
> +TRACE_EVENT(netfs_collect_gap,
> + TP_PROTO(const struct netfs_io_request *wreq,
> + const struct netfs_io_stream *stream,
> + unsigned long long jump_to, char type),
> +
> + TP_ARGS(wreq, stream, jump_to, type),
> +
> + TP_STRUCT__entry(
> + __field(unsigned int, wreq)
> + __field(unsigned char, stream)
> + __field(unsigned char, type)
> + __field(unsigned long long, from)
> + __field(unsigned long long, to)
> + ),
> +
> + TP_fast_assign(
> + __entry->wreq = wreq->debug_id;
> + __entry->stream = stream->stream_nr;
> + __entry->from = stream->collected_to;
> + __entry->to = jump_to;
> + __entry->type = type;
> + ),
> +
> + TP_printk("R=%08x[%x:] %llx->%llx %c",
> + __entry->wreq, __entry->stream,
> + __entry->from, __entry->to, __entry->type)
> + );
> +
> +TRACE_EVENT(netfs_collect_stream,
> + TP_PROTO(const struct netfs_io_request *wreq,
> + const struct netfs_io_stream *stream),
> +
> + TP_ARGS(wreq, stream),
> +
> + TP_STRUCT__entry(
> + __field(unsigned int, wreq)
> + __field(unsigned char, stream)
> + __field(unsigned long long, collected_to)
> + __field(unsigned long long, front)
> + ),
> +
> + TP_fast_assign(
> + __entry->wreq = wreq->debug_id;
> + __entry->stream = stream->stream_nr;
> + __entry->collected_to = stream->collected_to;
> + __entry->front = stream->front ? stream->front->start :
> UINT_MAX;
> + ),
> +
> + TP_printk("R=%08x[%x:] cto=%llx frn=%llx",
> + __entry->wreq, __entry->stream,
> + __entry->collected_to, __entry->front)
> + );
> +
> #undef EM
> #undef E_
> #endif /* _TRACE_NETFS_H */
>