Merge tag 'net-next-6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-nextgrafted

Pull networking updates from Jakub Kicinski:
 "Core:

   - Add dedicated kmem_cache for typical/small skb->head, avoid having
     to access struct page at kfree time, and improve memory use.

   - Introduce sysctl to set default RPS configuration for new netdevs.

   - Define Netlink protocol specification format which can be used to
     describe messages used by each family and auto-generate parsers.
     Add tools for generating kernel data structures and uAPI headers.

   - Expose all net/core sysctls inside netns.

   - Remove 4s sleep in netpoll if carrier is instantly detected on
     boot.

   - Add configurable limit of MDB entries per port, and port-vlan.

   - Continue populating drop reasons throughout the stack.

   - Retire a handful of legacy Qdiscs and classifiers.

  Protocols:

   - Support IPv4 big TCP (TSO frames larger than 64kB).

   - Add IP_LOCAL_PORT_RANGE socket option, to control local port range
     on socket by socket basis.

   - Track and report in procfs number of MPTCP sockets used.

   - Support mixing IPv4 and IPv6 flows in the in-kernel MPTCP path
     manager.

   - IPv6: don't check net.ipv6.route.max_size and rely on garbage
     collection to free memory (similarly to IPv4).

   - Support Penultimate Segment Pop (PSP) flavor in SRv6 (RFC8986).

   - ICMP: add per-rate limit counters.

   - Add support for user scanning requests in ieee802154.

   - Remove static WEP support.

   - Support minimal Wi-Fi 7 Extremely High Throughput (EHT) rate
     reporting.

   - WiFi 7 EHT channel puncturing support (client & AP).

  BPF:

   - Add a rbtree data structure following the "next-gen data structure"
     precedent set by recently added linked list, that is, by using
     kfunc + kptr instead of adding a new BPF map type.

   - Expose XDP hints via kfuncs with initial support for RX hash and
     timestamp metadata.

   - Add BPF_F_NO_TUNNEL_KEY extension to bpf_skb_set_tunnel_key to
     better support decap on GRE tunnel devices not operating in collect
     metadata.

   - Improve x86 JIT's codegen for PROBE_MEM runtime error checks.

   - Remove the need for trace_printk_lock for bpf_trace_printk and
     bpf_trace_vprintk helpers.

   - Extend libbpf's bpf_tracing.h support for tracing arguments of
     kprobes/uprobes and syscall as a special case.

   - Significantly reduce the search time for module symbols by
     livepatch and BPF.

   - Enable cpumasks to be used as kptrs, which is useful for tracing
     programs tracking which tasks end up running on which CPUs in
     different time intervals.

   - Add support for BPF trampoline on s390x and riscv64.

   - Add capability to export the XDP features supported by the NIC.

   - Add __bpf_kfunc tag for marking kernel functions as kfuncs.

   - Add cgroup.memory=nobpf kernel parameter option to disable BPF
     memory accounting for container environments.

  Netfilter:

   - Remove the CLUSTERIP target. It has been marked as obsolete for
     years, and we still have WARN splats wrt races of the out-of-band
     /proc interface installed by this target.

   - Add 'destroy' commands to nf_tables. They are identical to the
     existing 'delete' commands, but do not return an error if the
     referenced object (set, chain, rule...) did not exist.

  Driver API:

   - Improve cpumask_local_spread() locality to help NICs set the right
     IRQ affinity on AMD platforms.

   - Separate C22 and C45 MDIO bus transactions more clearly.

   - Introduce new DCB table to control DSCP rewrite on egress.

   - Support configuration of Physical Layer Collision Avoidance (PLCA)
     Reconciliation Sublayer (RS) (802.3cg-2019). Modern version of
     shared medium Ethernet.

   - Support for MAC Merge layer (IEEE 802.3-2018 clause 99). Allowing
     preemption of low priority frames by high priority frames.

   - Add support for controlling MACSec offload using netlink SET.

   - Rework devlink instance refcounts to allow registration and
     de-registration under the instance lock. Split the code into
     multiple files, drop some of the unnecessarily granular locks and
     factor out common parts of netlink operation handling.

   - Add TX frame aggregation parameters (for USB drivers).

   - Add a new attr TCA_EXT_WARN_MSG to report TC (offload) warning
     messages with notifications for debug.

   - Allow offloading of UDP NEW connections via act_ct.

   - Add support for per action HW stats in TC.

   - Support hardware miss to TC action (continue processing in SW from
     a specific point in the action chain).

   - Warn if old Wireless Extension user space interface is used with
     modern cfg80211/mac80211 drivers. Do not support Wireless
     Extensions for Wi-Fi 7 devices at all. Everyone should switch to
     using nl80211 interface instead.

   - Improve the CAN bit timing configuration. Use extack to return
     error messages directly to user space, update the SJW handling,
     including the definition of a new default value that will benefit
     CAN-FD controllers, by increasing their oscillator tolerance.

  New hardware / drivers:

   - Ethernet:
      - nVidia BlueField-3 support (control traffic driver)
      - Ethernet support for imx93 SoCs
      - Motorcomm yt8531 gigabit Ethernet PHY
      - onsemi NCN26000 10BASE-T1S PHY (with support for PLCA)
      - Microchip LAN8841 PHY (incl. cable diagnostics and PTP)
      - Amlogic gxl MDIO mux

   - WiFi:
      - RealTek RTL8188EU (rtl8xxxu)
      - Qualcomm Wi-Fi 7 devices (ath12k)

   - CAN:
      - Renesas R-Car V4H

  Drivers:

   - Bluetooth:
      - Set Per Platform Antenna Gain (PPAG) for Intel controllers.

   - Ethernet NICs:
      - Intel (1G, igc):
         - support TSN / Qbv / packet scheduling features of i226 model
      - Intel (100G, ice):
         - use GNSS subsystem instead of TTY
         - multi-buffer XDP support
         - extend support for GPIO pins to E823 devices
      - nVidia/Mellanox:
         - update the shared buffer configuration on PFC commands
         - implement PTP adjphase function for HW offset control
         - TC support for Geneve and GRE with VF tunnel offload
         - more efficient crypto key management method
         - multi-port eswitch support
      - Netronome/Corigine:
         - add DCB IEEE support
         - support IPsec offloading for NFP3800
      - Freescale/NXP (enetc):
         - support XDP_REDIRECT for XDP non-linear buffers
         - improve reconfig, avoid link flap and waiting for idle
         - support MAC Merge layer
      - Other NICs:
         - sfc/ef100: add basic devlink support for ef100
         - ionic: rx_push mode operation (writing descriptors via MMIO)
         - bnxt: use the auxiliary bus abstraction for RDMA
         - r8169: disable ASPM and reset bus in case of tx timeout
         - cpsw: support QSGMII mode for J721e CPSW9G
         - cpts: support pulse-per-second output
         - ngbe: add an mdio bus driver
         - usbnet: optimize usbnet_bh() by avoiding unnecessary queuing
         - r8152: handle devices with FW with NCM support
         - amd-xgbe: support 10Mbps, 2.5GbE speeds and rx-adaptation
         - virtio-net: support multi buffer XDP
         - virtio/vsock: replace virtio_vsock_pkt with sk_buff
         - tsnep: XDP support

   - Ethernet high-speed switches:
      - nVidia/Mellanox (mlxsw):
         - add support for latency TLV (in FW control messages)
      - Microchip (sparx5):
         - separate explicit and implicit traffic forwarding rules, make
           the implicit rules always active
         - add support for egress DSCP rewrite
         - IS0 VCAP support (Ingress Classification)
         - IS2 VCAP filters (protos, L3 addrs, L4 ports, flags, ToS
           etc.)
         - ES2 VCAP support (Egress Access Control)
         - support for Per-Stream Filtering and Policing (802.1Q,
           8.6.5.1)

   - Ethernet embedded switches:
      - Marvell (mv88e6xxx):
         - add MAB (port auth) offload support
         - enable PTP receive for mv88e6390
      - NXP (ocelot):
         - support MAC Merge layer
         - support for the the vsc7512 internal copper phys
      - Microchip:
         - lan9303: convert to PHYLINK
         - lan966x: support TC flower filter statistics
         - lan937x: PTP support for KSZ9563/KSZ8563 and LAN937x
         - lan937x: support Credit Based Shaper configuration
         - ksz9477: support Energy Efficient Ethernet
      - other:
         - qca8k: convert to regmap read/write API, use bulk operations
         - rswitch: Improve TX timestamp accuracy

   - Intel WiFi (iwlwifi):
      - EHT (Wi-Fi 7) rate reporting
      - STEP equalizer support: transfer some STEP (connection to radio
        on platforms with integrated wifi) related parameters from the
        BIOS to the firmware.

   - Qualcomm 802.11ax WiFi (ath11k):
      - IPQ5018 support
      - Fine Timing Measurement (FTM) responder role support
      - channel 177 support

   - MediaTek WiFi (mt76):
      - per-PHY LED support
      - mt7996: EHT (Wi-Fi 7) support
      - Wireless Ethernet Dispatch (WED) reset support
      - switch to using page pool allocator

   - RealTek WiFi (rtw89):
      - support new version of Bluetooth co-existance

   - Mobile:
      - rmnet: support TX aggregation"

* tag 'net-next-6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next: (1872 commits)
  page_pool: add a comment explaining the fragment counter usage
  net: ethtool: fix __ethtool_dev_mm_supported() implementation
  ethtool: pse-pd: Fix double word in comments
  xsk: add linux/vmalloc.h to xsk.c
  sefltests: netdevsim: wait for devlink instance after netns removal
  selftest: fib_tests: Always cleanup before exit
  net/mlx5e: Align IPsec ASO result memory to be as required by hardware
  net/mlx5e: TC, Set CT miss to the specific ct action instance
  net/mlx5e: Rename CHAIN_TO_REG to MAPPED_OBJ_TO_REG
  net/mlx5: Refactor tc miss handling to a single function
  net/mlx5: Kconfig: Make tc offload depend on tc skb extension
  net/sched: flower: Support hardware miss to tc action
  net/sched: flower: Move filter handle initialization earlier
  net/sched: cls_api: Support hardware miss to tc action
  net/sched: Rename user cookie and act cookie
  sfc: fix builds without CONFIG_RTC_LIB
  sfc: clean up some inconsistent indentings
  net/mlx4_en: Introduce flexible array to silence overflow warning
  net: lan966x: Fix possible deadlock inside PTP
  net/ulp: Remove redundant ->clone() test in inet_clone_ulp().
  ...

1 files changed, 433 insertions, 0 deletions

diff --git a/fs/netfs/buffered_read.c b/fs/netfs/buffered_read.c
new file mode 100644
index 000000000..7679a68e8
--- /dev/null
+++ b/fs/netfs/buffered_read.c
@@ -0,0 +1,433 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* Network filesystem high-level buffered read support.
+ *
+ * Copyright (C) 2021 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ */
+
+#include <linux/export.h>
+#include <linux/task_io_accounting_ops.h>
+#include "internal.h"
+
+/*
+ * Unlock the folios in a read operation.  We need to set PG_fscache on any
+ * folios we're going to write back before we unlock them.
+ */
+void netfs_rreq_unlock_folios(struct netfs_io_request *rreq)
+{
+	struct netfs_io_subrequest *subreq;
+	struct folio *folio;
+	pgoff_t start_page = rreq->start / PAGE_SIZE;
+	pgoff_t last_page = ((rreq->start + rreq->len) / PAGE_SIZE) - 1;
+	size_t account = 0;
+	bool subreq_failed = false;
+
+	XA_STATE(xas, &rreq->mapping->i_pages, start_page);
+
+	if (test_bit(NETFS_RREQ_FAILED, &rreq->flags)) {
+		__clear_bit(NETFS_RREQ_COPY_TO_CACHE, &rreq->flags);
+		list_for_each_entry(subreq, &rreq->subrequests, rreq_link) {
+			__clear_bit(NETFS_SREQ_COPY_TO_CACHE, &subreq->flags);
+		}
+	}
+
+	/* Walk through the pagecache and the I/O request lists simultaneously.
+	 * We may have a mixture of cached and uncached sections and we only
+	 * really want to write out the uncached sections.  This is slightly
+	 * complicated by the possibility that we might have huge pages with a
+	 * mixture inside.
+	 */
+	subreq = list_first_entry(&rreq->subrequests,
+				  struct netfs_io_subrequest, rreq_link);
+	subreq_failed = (subreq->error < 0);
+
+	trace_netfs_rreq(rreq, netfs_rreq_trace_unlock);
+
+	rcu_read_lock();
+	xas_for_each(&xas, folio, last_page) {
+		loff_t pg_end;
+		bool pg_failed = false;
+
+		if (xas_retry(&xas, folio))
+			continue;
+
+		pg_end = folio_pos(folio) + folio_size(folio) - 1;
+
+		for (;;) {
+			loff_t sreq_end;
+
+			if (!subreq) {
+				pg_failed = true;
+				break;
+			}
+			if (test_bit(NETFS_SREQ_COPY_TO_CACHE, &subreq->flags))
+				folio_start_fscache(folio);
+			pg_failed |= subreq_failed;
+			sreq_end = subreq->start + subreq->len - 1;
+			if (pg_end < sreq_end)
+				break;
+
+			account += subreq->transferred;
+			if (!list_is_last(&subreq->rreq_link, &rreq->subrequests)) {
+				subreq = list_next_entry(subreq, rreq_link);
+				subreq_failed = (subreq->error < 0);
+			} else {
+				subreq = NULL;
+				subreq_failed = false;
+			}
+
+			if (pg_end == sreq_end)
+				break;
+		}
+
+		if (!pg_failed) {
+			flush_dcache_folio(folio);
+			folio_mark_uptodate(folio);
+		}
+
+		if (!test_bit(NETFS_RREQ_DONT_UNLOCK_FOLIOS, &rreq->flags)) {
+			if (folio_index(folio) == rreq->no_unlock_folio &&
+			    test_bit(NETFS_RREQ_NO_UNLOCK_FOLIO, &rreq->flags))
+				_debug("no unlock");
+			else
+				folio_unlock(folio);
+		}
+	}
+	rcu_read_unlock();
+
+	task_io_account_read(account);
+	if (rreq->netfs_ops->done)
+		rreq->netfs_ops->done(rreq);
+}
+
+static void netfs_cache_expand_readahead(struct netfs_io_request *rreq,
+					 loff_t *_start, size_t *_len, loff_t i_size)
+{
+	struct netfs_cache_resources *cres = &rreq->cache_resources;
+
+	if (cres->ops && cres->ops->expand_readahead)
+		cres->ops->expand_readahead(cres, _start, _len, i_size);
+}
+
+static void netfs_rreq_expand(struct netfs_io_request *rreq,
+			      struct readahead_control *ractl)
+{
+	/* Give the cache a chance to change the request parameters.  The
+	 * resultant request must contain the original region.
+	 */
+	netfs_cache_expand_readahead(rreq, &rreq->start, &rreq->len, rreq->i_size);
+
+	/* Give the netfs a chance to change the request parameters.  The
+	 * resultant request must contain the original region.
+	 */
+	if (rreq->netfs_ops->expand_readahead)
+		rreq->netfs_ops->expand_readahead(rreq);
+
+	/* Expand the request if the cache wants it to start earlier.  Note
+	 * that the expansion may get further extended if the VM wishes to
+	 * insert THPs and the preferred start and/or end wind up in the middle
+	 * of THPs.
+	 *
+	 * If this is the case, however, the THP size should be an integer
+	 * multiple of the cache granule size, so we get a whole number of
+	 * granules to deal with.
+	 */
+	if (rreq->start  != readahead_pos(ractl) ||
+	    rreq->len != readahead_length(ractl)) {
+		readahead_expand(ractl, rreq->start, rreq->len);
+		rreq->start  = readahead_pos(ractl);
+		rreq->len = readahead_length(ractl);
+
+		trace_netfs_read(rreq, readahead_pos(ractl), readahead_length(ractl),
+				 netfs_read_trace_expanded);
+	}
+}
+
+/**
+ * netfs_readahead - Helper to manage a read request
+ * @ractl: The description of the readahead request
+ *
+ * Fulfil a readahead request by drawing data from the cache if possible, or
+ * the netfs if not.  Space beyond the EOF is zero-filled.  Multiple I/O
+ * requests from different sources will get munged together.  If necessary, the
+ * readahead window can be expanded in either direction to a more convenient
+ * alighment for RPC efficiency or to make storage in the cache feasible.
+ *
+ * The calling netfs must initialise a netfs context contiguous to the vfs
+ * inode before calling this.
+ *
+ * This is usable whether or not caching is enabled.
+ */
+void netfs_readahead(struct readahead_control *ractl)
+{
+	struct netfs_io_request *rreq;
+	struct netfs_inode *ctx = netfs_inode(ractl->mapping->host);
+	int ret;
+
+	_enter("%lx,%x", readahead_index(ractl), readahead_count(ractl));
+
+	if (readahead_count(ractl) == 0)
+		return;
+
+	rreq = netfs_alloc_request(ractl->mapping, ractl->file,
+				   readahead_pos(ractl),
+				   readahead_length(ractl),
+				   NETFS_READAHEAD);
+	if (IS_ERR(rreq))
+		return;
+
+	if (ctx->ops->begin_cache_operation) {
+		ret = ctx->ops->begin_cache_operation(rreq);
+		if (ret == -ENOMEM || ret == -EINTR || ret == -ERESTARTSYS)
+			goto cleanup_free;
+	}
+
+	netfs_stat(&netfs_n_rh_readahead);
+	trace_netfs_read(rreq, readahead_pos(ractl), readahead_length(ractl),
+			 netfs_read_trace_readahead);
+
+	netfs_rreq_expand(rreq, ractl);
+
+	/* Drop the refs on the folios here rather than in the cache or
+	 * filesystem.  The locks will be dropped in netfs_rreq_unlock().
+	 */
+	while (readahead_folio(ractl))
+		;
+
+	netfs_begin_read(rreq, false);
+	return;
+
+cleanup_free:
+	netfs_put_request(rreq, false, netfs_rreq_trace_put_failed);
+	return;
+}
+EXPORT_SYMBOL(netfs_readahead);
+
+/**
+ * netfs_read_folio - Helper to manage a read_folio request
+ * @file: The file to read from
+ * @folio: The folio to read
+ *
+ * Fulfil a read_folio request by drawing data from the cache if
+ * possible, or the netfs if not.  Space beyond the EOF is zero-filled.
+ * Multiple I/O requests from different sources will get munged together.
+ *
+ * The calling netfs must initialise a netfs context contiguous to the vfs
+ * inode before calling this.
+ *
+ * This is usable whether or not caching is enabled.
+ */
+int netfs_read_folio(struct file *file, struct folio *folio)
+{
+	struct address_space *mapping = folio_file_mapping(folio);
+	struct netfs_io_request *rreq;
+	struct netfs_inode *ctx = netfs_inode(mapping->host);
+	int ret;
+
+	_enter("%lx", folio_index(folio));
+
+	rreq = netfs_alloc_request(mapping, file,
+				   folio_file_pos(folio), folio_size(folio),
+				   NETFS_READPAGE);
+	if (IS_ERR(rreq)) {
+		ret = PTR_ERR(rreq);
+		goto alloc_error;
+	}
+
+	if (ctx->ops->begin_cache_operation) {
+		ret = ctx->ops->begin_cache_operation(rreq);
+		if (ret == -ENOMEM || ret == -EINTR || ret == -ERESTARTSYS)
+			goto discard;
+	}
+
+	netfs_stat(&netfs_n_rh_readpage);
+	trace_netfs_read(rreq, rreq->start, rreq->len, netfs_read_trace_readpage);
+	return netfs_begin_read(rreq, true);
+
+discard:
+	netfs_put_request(rreq, false, netfs_rreq_trace_put_discard);
+alloc_error:
+	folio_unlock(folio);
+	return ret;
+}
+EXPORT_SYMBOL(netfs_read_folio);
+
+/*
+ * Prepare a folio for writing without reading first
+ * @folio: The folio being prepared
+ * @pos: starting position for the write
+ * @len: length of write
+ * @always_fill: T if the folio should always be completely filled/cleared
+ *
+ * In some cases, write_begin doesn't need to read at all:
+ * - full folio write
+ * - write that lies in a folio that is completely beyond EOF
+ * - write that covers the folio from start to EOF or beyond it
+ *
+ * If any of these criteria are met, then zero out the unwritten parts
+ * of the folio and return true. Otherwise, return false.
+ */
+static bool netfs_skip_folio_read(struct folio *folio, loff_t pos, size_t len,
+				 bool always_fill)
+{
+	struct inode *inode = folio_inode(folio);
+	loff_t i_size = i_size_read(inode);
+	size_t offset = offset_in_folio(folio, pos);
+	size_t plen = folio_size(folio);
+
+	if (unlikely(always_fill)) {
+		if (pos - offset + len <= i_size)
+			return false; /* Page entirely before EOF */
+		zero_user_segment(&folio->page, 0, plen);
+		folio_mark_uptodate(folio);
+		return true;
+	}
+
+	/* Full folio write */
+	if (offset == 0 && len >= plen)
+		return true;
+
+	/* Page entirely beyond the end of the file */
+	if (pos - offset >= i_size)
+		goto zero_out;
+
+	/* Write that covers from the start of the folio to EOF or beyond */
+	if (offset == 0 && (pos + len) >= i_size)
+		goto zero_out;
+
+	return false;
+zero_out:
+	zero_user_segments(&folio->page, 0, offset, offset + len, plen);
+	return true;
+}
+
+/**
+ * netfs_write_begin - Helper to prepare for writing
+ * @ctx: The netfs context
+ * @file: The file to read from
+ * @mapping: The mapping to read from
+ * @pos: File position at which the write will begin
+ * @len: The length of the write (may extend beyond the end of the folio chosen)
+ * @_folio: Where to put the resultant folio
+ * @_fsdata: Place for the netfs to store a cookie
+ *
+ * Pre-read data for a write-begin request by drawing data from the cache if
+ * possible, or the netfs if not.  Space beyond the EOF is zero-filled.
+ * Multiple I/O requests from different sources will get munged together.  If
+ * necessary, the readahead window can be expanded in either direction to a
+ * more convenient alighment for RPC efficiency or to make storage in the cache
+ * feasible.
+ *
+ * The calling netfs must provide a table of operations, only one of which,
+ * issue_op, is mandatory.
+ *
+ * The check_write_begin() operation can be provided to check for and flush
+ * conflicting writes once the folio is grabbed and locked.  It is passed a
+ * pointer to the fsdata cookie that gets returned to the VM to be passed to
+ * write_end.  It is permitted to sleep.  It should return 0 if the request
+ * should go ahead or it may return an error.  It may also unlock and put the
+ * folio, provided it sets ``*foliop`` to NULL, in which case a return of 0
+ * will cause the folio to be re-got and the process to be retried.
+ *
+ * The calling netfs must initialise a netfs context contiguous to the vfs
+ * inode before calling this.
+ *
+ * This is usable whether or not caching is enabled.
+ */
+int netfs_write_begin(struct netfs_inode *ctx,
+		      struct file *file, struct address_space *mapping,
+		      loff_t pos, unsigned int len, struct folio **_folio,
+		      void **_fsdata)
+{
+	struct netfs_io_request *rreq;
+	struct folio *folio;
+	unsigned int fgp_flags = FGP_LOCK | FGP_WRITE | FGP_CREAT | FGP_STABLE;
+	pgoff_t index = pos >> PAGE_SHIFT;
+	int ret;
+
+	DEFINE_READAHEAD(ractl, file, NULL, mapping, index);
+
+retry:
+	folio = __filemap_get_folio(mapping, index, fgp_flags,
+				    mapping_gfp_mask(mapping));
+	if (!folio)
+		return -ENOMEM;
+
+	if (ctx->ops->check_write_begin) {
+		/* Allow the netfs (eg. ceph) to flush conflicts. */
+		ret = ctx->ops->check_write_begin(file, pos, len, &folio, _fsdata);
+		if (ret < 0) {
+			trace_netfs_failure(NULL, NULL, ret, netfs_fail_check_write_begin);
+			goto error;
+		}
+		if (!folio)
+			goto retry;
+	}
+
+	if (folio_test_uptodate(folio))
+		goto have_folio;
+
+	/* If the page is beyond the EOF, we want to clear it - unless it's
+	 * within the cache granule containing the EOF, in which case we need
+	 * to preload the granule.
+	 */
+	if (!netfs_is_cache_enabled(ctx) &&
+	    netfs_skip_folio_read(folio, pos, len, false)) {
+		netfs_stat(&netfs_n_rh_write_zskip);
+		goto have_folio_no_wait;
+	}
+
+	rreq = netfs_alloc_request(mapping, file,
+				   folio_file_pos(folio), folio_size(folio),
+				   NETFS_READ_FOR_WRITE);
+	if (IS_ERR(rreq)) {
+		ret = PTR_ERR(rreq);
+		goto error;
+	}
+	rreq->no_unlock_folio	= folio_index(folio);
+	__set_bit(NETFS_RREQ_NO_UNLOCK_FOLIO, &rreq->flags);
+
+	if (ctx->ops->begin_cache_operation) {
+		ret = ctx->ops->begin_cache_operation(rreq);
+		if (ret == -ENOMEM || ret == -EINTR || ret == -ERESTARTSYS)
+			goto error_put;
+	}
+
+	netfs_stat(&netfs_n_rh_write_begin);
+	trace_netfs_read(rreq, pos, len, netfs_read_trace_write_begin);
+
+	/* Expand the request to meet caching requirements and download
+	 * preferences.
+	 */
+	ractl._nr_pages = folio_nr_pages(folio);
+	netfs_rreq_expand(rreq, &ractl);
+
+	/* We hold the folio locks, so we can drop the references */
+	folio_get(folio);
+	while (readahead_folio(&ractl))
+		;
+
+	ret = netfs_begin_read(rreq, true);
+	if (ret < 0)
+		goto error;
+
+have_folio:
+	ret = folio_wait_fscache_killable(folio);
+	if (ret < 0)
+		goto error;
+have_folio_no_wait:
+	*_folio = folio;
+	_leave(" = 0");
+	return 0;
+
+error_put:
+	netfs_put_request(rreq, false, netfs_rreq_trace_put_failed);
+error:
+	if (folio) {
+		folio_unlock(folio);
+		folio_put(folio);
+	}
+	_leave(" = %d", ret);
+	return ret;
+}
+EXPORT_SYMBOL(netfs_write_begin);