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, 525 insertions, 0 deletions

diff --git a/fs/befs/datastream.c b/fs/befs/datastream.c
new file mode 100644
index 000000000..97719a7c7
--- /dev/null
+++ b/fs/befs/datastream.c
@@ -0,0 +1,525 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * linux/fs/befs/datastream.c
+ *
+ * Copyright (C) 2001 Will Dyson <will_dyson@pobox.com>
+ *
+ * Based on portions of file.c by Makoto Kato <m_kato@ga2.so-net.ne.jp>
+ *
+ * Many thanks to Dominic Giampaolo, author of "Practical File System
+ * Design with the Be File System", for such a helpful book.
+ *
+ */
+
+#include <linux/kernel.h>
+#include <linux/buffer_head.h>
+#include <linux/string.h>
+
+#include "befs.h"
+#include "datastream.h"
+#include "io.h"
+
+const befs_inode_addr BAD_IADDR = { 0, 0, 0 };
+
+static int befs_find_brun_direct(struct super_block *sb,
+				 const befs_data_stream *data,
+				 befs_blocknr_t blockno, befs_block_run *run);
+
+static int befs_find_brun_indirect(struct super_block *sb,
+				   const befs_data_stream *data,
+				   befs_blocknr_t blockno,
+				   befs_block_run *run);
+
+static int befs_find_brun_dblindirect(struct super_block *sb,
+				      const befs_data_stream *data,
+				      befs_blocknr_t blockno,
+				      befs_block_run *run);
+
+/**
+ * befs_read_datastream - get buffer_head containing data, starting from pos.
+ * @sb: Filesystem superblock
+ * @ds: datastream to find data with
+ * @pos: start of data
+ * @off: offset of data in buffer_head->b_data
+ *
+ * Returns pointer to buffer_head containing data starting with offset @off,
+ * if you don't need to know offset just set @off = NULL.
+ */
+struct buffer_head *
+befs_read_datastream(struct super_block *sb, const befs_data_stream *ds,
+		     befs_off_t pos, uint *off)
+{
+	struct buffer_head *bh;
+	befs_block_run run;
+	befs_blocknr_t block;	/* block coresponding to pos */
+
+	befs_debug(sb, "---> %s %llu", __func__, pos);
+	block = pos >> BEFS_SB(sb)->block_shift;
+	if (off)
+		*off = pos - (block << BEFS_SB(sb)->block_shift);
+
+	if (befs_fblock2brun(sb, ds, block, &run) != BEFS_OK) {
+		befs_error(sb, "BeFS: Error finding disk addr of block %lu",
+			   (unsigned long)block);
+		befs_debug(sb, "<--- %s ERROR", __func__);
+		return NULL;
+	}
+	bh = befs_bread_iaddr(sb, run);
+	if (!bh) {
+		befs_error(sb, "BeFS: Error reading block %lu from datastream",
+			   (unsigned long)block);
+		return NULL;
+	}
+
+	befs_debug(sb, "<--- %s read data, starting at %llu", __func__, pos);
+
+	return bh;
+}
+
+/**
+ * befs_fblock2brun - give back block run for fblock
+ * @sb: the superblock
+ * @data: datastream to read from
+ * @fblock: the blocknumber with the file position to find
+ * @run: The found run is passed back through this pointer
+ *
+ * Takes a file position and gives back a brun who's starting block
+ * is block number fblock of the file.
+ *
+ * Returns BEFS_OK or BEFS_ERR.
+ *
+ * Calls specialized functions for each of the three possible
+ * datastream regions.
+ */
+int
+befs_fblock2brun(struct super_block *sb, const befs_data_stream *data,
+		 befs_blocknr_t fblock, befs_block_run *run)
+{
+	int err;
+	befs_off_t pos = fblock << BEFS_SB(sb)->block_shift;
+
+	if (pos < data->max_direct_range) {
+		err = befs_find_brun_direct(sb, data, fblock, run);
+
+	} else if (pos < data->max_indirect_range) {
+		err = befs_find_brun_indirect(sb, data, fblock, run);
+
+	} else if (pos < data->max_double_indirect_range) {
+		err = befs_find_brun_dblindirect(sb, data, fblock, run);
+
+	} else {
+		befs_error(sb,
+			   "befs_fblock2brun() was asked to find block %lu, "
+			   "which is not mapped by the datastream\n",
+			   (unsigned long)fblock);
+		err = BEFS_ERR;
+	}
+	return err;
+}
+
+/**
+ * befs_read_lsmylink - read long symlink from datastream.
+ * @sb: Filesystem superblock
+ * @ds: Datastream to read from
+ * @buff: Buffer in which to place long symlink data
+ * @len: Length of the long symlink in bytes
+ *
+ * Returns the number of bytes read
+ */
+size_t
+befs_read_lsymlink(struct super_block *sb, const befs_data_stream *ds,
+		   void *buff, befs_off_t len)
+{
+	befs_off_t bytes_read = 0;	/* bytes readed */
+	u16 plen;
+	struct buffer_head *bh;
+
+	befs_debug(sb, "---> %s length: %llu", __func__, len);
+
+	while (bytes_read < len) {
+		bh = befs_read_datastream(sb, ds, bytes_read, NULL);
+		if (!bh) {
+			befs_error(sb, "BeFS: Error reading datastream block "
+				   "starting from %llu", bytes_read);
+			befs_debug(sb, "<--- %s ERROR", __func__);
+			return bytes_read;
+
+		}
+		plen = ((bytes_read + BEFS_SB(sb)->block_size) < len) ?
+		    BEFS_SB(sb)->block_size : len - bytes_read;
+		memcpy(buff + bytes_read, bh->b_data, plen);
+		brelse(bh);
+		bytes_read += plen;
+	}
+
+	befs_debug(sb, "<--- %s read %u bytes", __func__, (unsigned int)
+		   bytes_read);
+	return bytes_read;
+}
+
+/**
+ * befs_count_blocks - blocks used by a file
+ * @sb: Filesystem superblock
+ * @ds: Datastream of the file
+ *
+ * Counts the number of fs blocks that the file represented by
+ * inode occupies on the filesystem, counting both regular file
+ * data and filesystem metadata (and eventually attribute data
+ * when we support attributes)
+*/
+
+befs_blocknr_t
+befs_count_blocks(struct super_block *sb, const befs_data_stream *ds)
+{
+	befs_blocknr_t blocks;
+	befs_blocknr_t datablocks;	/* File data blocks */
+	befs_blocknr_t metablocks;	/* FS metadata blocks */
+	struct befs_sb_info *befs_sb = BEFS_SB(sb);
+
+	befs_debug(sb, "---> %s", __func__);
+
+	datablocks = ds->size >> befs_sb->block_shift;
+	if (ds->size & (befs_sb->block_size - 1))
+		datablocks += 1;
+
+	metablocks = 1;		/* Start with 1 block for inode */
+
+	/* Size of indirect block */
+	if (ds->size > ds->max_direct_range)
+		metablocks += ds->indirect.len;
+
+	/*
+	 * Double indir block, plus all the indirect blocks it maps.
+	 * In the double-indirect range, all block runs of data are
+	 * BEFS_DBLINDIR_BRUN_LEN blocks long. Therefore, we know
+	 * how many data block runs are in the double-indirect region,
+	 * and from that we know how many indirect blocks it takes to
+	 * map them. We assume that the indirect blocks are also
+	 * BEFS_DBLINDIR_BRUN_LEN blocks long.
+	 */
+	if (ds->size > ds->max_indirect_range && ds->max_indirect_range != 0) {
+		uint dbl_bytes;
+		uint dbl_bruns;
+		uint indirblocks;
+
+		dbl_bytes =
+		    ds->max_double_indirect_range - ds->max_indirect_range;
+		dbl_bruns =
+		    dbl_bytes / (befs_sb->block_size * BEFS_DBLINDIR_BRUN_LEN);
+		indirblocks = dbl_bruns / befs_iaddrs_per_block(sb);
+
+		metablocks += ds->double_indirect.len;
+		metablocks += indirblocks;
+	}
+
+	blocks = datablocks + metablocks;
+	befs_debug(sb, "<--- %s %u blocks", __func__, (unsigned int)blocks);
+
+	return blocks;
+}
+
+/**
+ * befs_find_brun_direct - find a direct block run in the datastream
+ * @sb: the superblock
+ * @data: the datastream
+ * @blockno: the blocknumber to find
+ * @run: The found run is passed back through this pointer
+ *
+ * Finds the block run that starts at file block number blockno
+ * in the file represented by the datastream data, if that
+ * blockno is in the direct region of the datastream.
+ *
+ * Return value is BEFS_OK if the blockrun is found, BEFS_ERR
+ * otherwise.
+ *
+ * Algorithm:
+ * Linear search. Checks each element of array[] to see if it
+ * contains the blockno-th filesystem block. This is necessary
+ * because the block runs map variable amounts of data. Simply
+ * keeps a count of the number of blocks searched so far (sum),
+ * incrementing this by the length of each block run as we come
+ * across it. Adds sum to *count before returning (this is so
+ * you can search multiple arrays that are logicaly one array,
+ * as in the indirect region code).
+ *
+ * When/if blockno is found, if blockno is inside of a block
+ * run as stored on disk, we offset the start and length members
+ * of the block run, so that blockno is the start and len is
+ * still valid (the run ends in the same place).
+ */
+static int
+befs_find_brun_direct(struct super_block *sb, const befs_data_stream *data,
+		      befs_blocknr_t blockno, befs_block_run *run)
+{
+	int i;
+	const befs_block_run *array = data->direct;
+	befs_blocknr_t sum;
+
+	befs_debug(sb, "---> %s, find %lu", __func__, (unsigned long)blockno);
+
+	for (i = 0, sum = 0; i < BEFS_NUM_DIRECT_BLOCKS;
+	     sum += array[i].len, i++) {
+		if (blockno >= sum && blockno < sum + (array[i].len)) {
+			int offset = blockno - sum;
+
+			run->allocation_group = array[i].allocation_group;
+			run->start = array[i].start + offset;
+			run->len = array[i].len - offset;
+
+			befs_debug(sb, "---> %s, "
+				   "found %lu at direct[%d]", __func__,
+				   (unsigned long)blockno, i);
+			return BEFS_OK;
+		}
+	}
+
+	befs_error(sb, "%s failed to find file block %lu", __func__,
+		   (unsigned long)blockno);
+	befs_debug(sb, "---> %s ERROR", __func__);
+	return BEFS_ERR;
+}
+
+/**
+ * befs_find_brun_indirect - find a block run in the datastream
+ * @sb: the superblock
+ * @data: the datastream
+ * @blockno: the blocknumber to find
+ * @run: The found run is passed back through this pointer
+ *
+ * Finds the block run that starts at file block number blockno
+ * in the file represented by the datastream data, if that
+ * blockno is in the indirect region of the datastream.
+ *
+ * Return value is BEFS_OK if the blockrun is found, BEFS_ERR
+ * otherwise.
+ *
+ * Algorithm:
+ * For each block in the indirect run of the datastream, read
+ * it in and search through it for search_blk.
+ *
+ * XXX:
+ * Really should check to make sure blockno is inside indirect
+ * region.
+ */
+static int
+befs_find_brun_indirect(struct super_block *sb,
+			const befs_data_stream *data,
+			befs_blocknr_t blockno,
+			befs_block_run *run)
+{
+	int i, j;
+	befs_blocknr_t sum = 0;
+	befs_blocknr_t indir_start_blk;
+	befs_blocknr_t search_blk;
+	struct buffer_head *indirblock;
+	befs_disk_block_run *array;
+
+	befs_block_run indirect = data->indirect;
+	befs_blocknr_t indirblockno = iaddr2blockno(sb, &indirect);
+	int arraylen = befs_iaddrs_per_block(sb);
+
+	befs_debug(sb, "---> %s, find %lu", __func__, (unsigned long)blockno);
+
+	indir_start_blk = data->max_direct_range >> BEFS_SB(sb)->block_shift;
+	search_blk = blockno - indir_start_blk;
+
+	/* Examine blocks of the indirect run one at a time */
+	for (i = 0; i < indirect.len; i++) {
+		indirblock = sb_bread(sb, indirblockno + i);
+		if (indirblock == NULL) {
+			befs_error(sb, "---> %s failed to read "
+				   "disk block %lu from the indirect brun",
+				   __func__, (unsigned long)indirblockno + i);
+			befs_debug(sb, "<--- %s ERROR", __func__);
+			return BEFS_ERR;
+		}
+
+		array = (befs_disk_block_run *) indirblock->b_data;
+
+		for (j = 0; j < arraylen; ++j) {
+			int len = fs16_to_cpu(sb, array[j].len);
+
+			if (search_blk >= sum && search_blk < sum + len) {
+				int offset = search_blk - sum;
+				run->allocation_group =
+				    fs32_to_cpu(sb, array[j].allocation_group);
+				run->start =
+				    fs16_to_cpu(sb, array[j].start) + offset;
+				run->len =
+				    fs16_to_cpu(sb, array[j].len) - offset;
+
+				brelse(indirblock);
+				befs_debug(sb,
+					   "<--- %s found file block "
+					   "%lu at indirect[%d]", __func__,
+					   (unsigned long)blockno,
+					   j + (i * arraylen));
+				return BEFS_OK;
+			}
+			sum += len;
+		}
+
+		brelse(indirblock);
+	}
+
+	/* Only fallthrough is an error */
+	befs_error(sb, "BeFS: %s failed to find "
+		   "file block %lu", __func__, (unsigned long)blockno);
+
+	befs_debug(sb, "<--- %s ERROR", __func__);
+	return BEFS_ERR;
+}
+
+/**
+ * befs_find_brun_dblindirect - find a block run in the datastream
+ * @sb: the superblock
+ * @data: the datastream
+ * @blockno: the blocknumber to find
+ * @run: The found run is passed back through this pointer
+ *
+ * Finds the block run that starts at file block number blockno
+ * in the file represented by the datastream data, if that
+ * blockno is in the double-indirect region of the datastream.
+ *
+ * Return value is BEFS_OK if the blockrun is found, BEFS_ERR
+ * otherwise.
+ *
+ * Algorithm:
+ * The block runs in the double-indirect region are different.
+ * They are always allocated 4 fs blocks at a time, so each
+ * block run maps a constant amount of file data. This means
+ * that we can directly calculate how many block runs into the
+ * double-indirect region we need to go to get to the one that
+ * maps a particular filesystem block.
+ *
+ * We do this in two stages. First we calculate which of the
+ * inode addresses in the double-indirect block will point us
+ * to the indirect block that contains the mapping for the data,
+ * then we calculate which of the inode addresses in that
+ * indirect block maps the data block we are after.
+ *
+ * Oh, and once we've done that, we actually read in the blocks
+ * that contain the inode addresses we calculated above. Even
+ * though the double-indirect run may be several blocks long,
+ * we can calculate which of those blocks will contain the index
+ * we are after and only read that one. We then follow it to
+ * the indirect block and perform a similar process to find
+ * the actual block run that maps the data block we are interested
+ * in.
+ *
+ * Then we offset the run as in befs_find_brun_array() and we are
+ * done.
+ */
+static int
+befs_find_brun_dblindirect(struct super_block *sb,
+			   const befs_data_stream *data,
+			   befs_blocknr_t blockno,
+			   befs_block_run *run)
+{
+	int dblindir_indx;
+	int indir_indx;
+	int offset;
+	int dbl_which_block;
+	int which_block;
+	int dbl_block_indx;
+	int block_indx;
+	off_t dblindir_leftover;
+	befs_blocknr_t blockno_at_run_start;
+	struct buffer_head *dbl_indir_block;
+	struct buffer_head *indir_block;
+	befs_block_run indir_run;
+	befs_disk_inode_addr *iaddr_array;
+
+	befs_blocknr_t indir_start_blk =
+	    data->max_indirect_range >> BEFS_SB(sb)->block_shift;
+
+	off_t dbl_indir_off = blockno - indir_start_blk;
+
+	/* number of data blocks mapped by each of the iaddrs in
+	 * the indirect block pointed to by the double indirect block
+	 */
+	size_t iblklen = BEFS_DBLINDIR_BRUN_LEN;
+
+	/* number of data blocks mapped by each of the iaddrs in
+	 * the double indirect block
+	 */
+	size_t diblklen = iblklen * befs_iaddrs_per_block(sb)
+	    * BEFS_DBLINDIR_BRUN_LEN;
+
+	befs_debug(sb, "---> %s find %lu", __func__, (unsigned long)blockno);
+
+	/* First, discover which of the double_indir->indir blocks
+	 * contains pos. Then figure out how much of pos that
+	 * accounted for. Then discover which of the iaddrs in
+	 * the indirect block contains pos.
+	 */
+
+	dblindir_indx = dbl_indir_off / diblklen;
+	dblindir_leftover = dbl_indir_off % diblklen;
+	indir_indx = dblindir_leftover / diblklen;
+
+	/* Read double indirect block */
+	dbl_which_block = dblindir_indx / befs_iaddrs_per_block(sb);
+	if (dbl_which_block > data->double_indirect.len) {
+		befs_error(sb, "The double-indirect index calculated by "
+			   "%s, %d, is outside the range "
+			   "of the double-indirect block", __func__,
+			   dblindir_indx);
+		return BEFS_ERR;
+	}
+
+	dbl_indir_block =
+	    sb_bread(sb, iaddr2blockno(sb, &data->double_indirect) +
+					dbl_which_block);
+	if (dbl_indir_block == NULL) {
+		befs_error(sb, "%s couldn't read the "
+			   "double-indirect block at blockno %lu", __func__,
+			   (unsigned long)
+			   iaddr2blockno(sb, &data->double_indirect) +
+			   dbl_which_block);
+		return BEFS_ERR;
+	}
+
+	dbl_block_indx =
+	    dblindir_indx - (dbl_which_block * befs_iaddrs_per_block(sb));
+	iaddr_array = (befs_disk_inode_addr *) dbl_indir_block->b_data;
+	indir_run = fsrun_to_cpu(sb, iaddr_array[dbl_block_indx]);
+	brelse(dbl_indir_block);
+
+	/* Read indirect block */
+	which_block = indir_indx / befs_iaddrs_per_block(sb);
+	if (which_block > indir_run.len) {
+		befs_error(sb, "The indirect index calculated by "
+			   "%s, %d, is outside the range "
+			   "of the indirect block", __func__, indir_indx);
+		return BEFS_ERR;
+	}
+
+	indir_block =
+	    sb_bread(sb, iaddr2blockno(sb, &indir_run) + which_block);
+	if (indir_block == NULL) {
+		befs_error(sb, "%s couldn't read the indirect block "
+			   "at blockno %lu", __func__, (unsigned long)
+			   iaddr2blockno(sb, &indir_run) + which_block);
+		return BEFS_ERR;
+	}
+
+	block_indx = indir_indx - (which_block * befs_iaddrs_per_block(sb));
+	iaddr_array = (befs_disk_inode_addr *) indir_block->b_data;
+	*run = fsrun_to_cpu(sb, iaddr_array[block_indx]);
+	brelse(indir_block);
+
+	blockno_at_run_start = indir_start_blk;
+	blockno_at_run_start += diblklen * dblindir_indx;
+	blockno_at_run_start += iblklen * indir_indx;
+	offset = blockno - blockno_at_run_start;
+
+	run->start += offset;
+	run->len -= offset;
+
+	befs_debug(sb, "Found file block %lu in double_indirect[%d][%d],"
+		   " double_indirect_leftover = %lu", (unsigned long)
+		   blockno, dblindir_indx, indir_indx, dblindir_leftover);
+
+	return BEFS_OK;
+}