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, 444 insertions, 0 deletions

diff --git a/arch/um/drivers/cow_user.c b/arch/um/drivers/cow_user.c
new file mode 100644
index 000000000..29b46581d
--- /dev/null
+++ b/arch/um/drivers/cow_user.c
@@ -0,0 +1,444 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2007 Jeff Dike (jdike@{linux.intel,addtoit}.com)
+ */
+
+/*
+ * _XOPEN_SOURCE is needed for pread, but we define _GNU_SOURCE, which defines
+ * that.
+ */
+#include <unistd.h>
+#include <errno.h>
+#include <string.h>
+#include <arpa/inet.h>
+#include <endian.h>
+#include "cow.h"
+#include "cow_sys.h"
+
+#define PATH_LEN_V1 256
+
+/* unsigned time_t works until year 2106 */
+typedef __u32 time32_t;
+
+struct cow_header_v1 {
+	__s32 magic;
+	__s32 version;
+	char backing_file[PATH_LEN_V1];
+	time32_t mtime;
+	__u64 size;
+	__s32 sectorsize;
+} __attribute__((packed));
+
+/*
+ * Define PATH_LEN_V3 as the usual value of MAXPATHLEN, just hard-code it in
+ * case other systems have different values for MAXPATHLEN.
+ *
+ * The same must hold for V2 - we want file format compatibility, not anything
+ * else.
+ */
+#define PATH_LEN_V3 4096
+#define PATH_LEN_V2 PATH_LEN_V3
+
+struct cow_header_v2 {
+	__u32 magic;
+	__u32 version;
+	char backing_file[PATH_LEN_V2];
+	time32_t mtime;
+	__u64 size;
+	__s32 sectorsize;
+} __attribute__((packed));
+
+/*
+ * Changes from V2 -
+ *	PATH_LEN_V3 as described above
+ *	Explicitly specify field bit lengths for systems with different
+ *		lengths for the usual C types.  Not sure whether char or
+ *		time_t should be changed, this can be changed later without
+ *		breaking compatibility
+ *	Add alignment field so that different alignments can be used for the
+ *		bitmap and data
+ * 	Add cow_format field to allow for the possibility of different ways
+ *		of specifying the COW blocks.  For now, the only value is 0,
+ * 		for the traditional COW bitmap.
+ *	Move the backing_file field to the end of the header.  This allows
+ *		for the possibility of expanding it into the padding required
+ *		by the bitmap alignment.
+ * 	The bitmap and data portions of the file will be aligned as specified
+ * 		by the alignment field.  This is to allow COW files to be
+ *		put on devices with restrictions on access alignments, such as
+ *		/dev/raw, with a 512 byte alignment restriction.  This also
+ *		allows the data to be more aligned more strictly than on
+ *		sector boundaries.  This is needed for ubd-mmap, which needs
+ *		the data to be page aligned.
+ *	Fixed (finally!) the rounding bug
+ */
+
+/*
+ * Until Dec2005, __attribute__((packed)) was left out from the below
+ * definition, leading on 64-bit systems to 4 bytes of padding after mtime, to
+ * align size to 8-byte alignment.  This shifted all fields above (no padding
+ * was present on 32-bit, no other padding was added).
+ *
+ * However, this _can be detected_: it means that cow_format (always 0 until
+ * now) is shifted onto the first 4 bytes of backing_file, where it is otherwise
+ * impossible to find 4 zeros. -bb */
+
+struct cow_header_v3 {
+	__u32 magic;
+	__u32 version;
+	__u32 mtime;
+	__u64 size;
+	__u32 sectorsize;
+	__u32 alignment;
+	__u32 cow_format;
+	char backing_file[PATH_LEN_V3];
+} __attribute__((packed));
+
+/* This is the broken layout used by some 64-bit binaries. */
+struct cow_header_v3_broken {
+	__u32 magic;
+	__u32 version;
+	__s64 mtime;
+	__u64 size;
+	__u32 sectorsize;
+	__u32 alignment;
+	__u32 cow_format;
+	char backing_file[PATH_LEN_V3];
+};
+
+/* COW format definitions - for now, we have only the usual COW bitmap */
+#define COW_BITMAP 0
+
+union cow_header {
+	struct cow_header_v1 v1;
+	struct cow_header_v2 v2;
+	struct cow_header_v3 v3;
+	struct cow_header_v3_broken v3_b;
+};
+
+#define COW_MAGIC 0x4f4f4f4d  /* MOOO */
+#define COW_VERSION 3
+
+#define DIV_ROUND(x, len) (((x) + (len) - 1) / (len))
+#define ROUND_UP(x, align) DIV_ROUND(x, align) * (align)
+
+void cow_sizes(int version, __u64 size, int sectorsize, int align,
+	       int bitmap_offset, unsigned long *bitmap_len_out,
+	       int *data_offset_out)
+{
+	if (version < 3) {
+		*bitmap_len_out = (size + sectorsize - 1) / (8 * sectorsize);
+
+		*data_offset_out = bitmap_offset + *bitmap_len_out;
+		*data_offset_out = (*data_offset_out + sectorsize - 1) /
+			sectorsize;
+		*data_offset_out *= sectorsize;
+	}
+	else {
+		*bitmap_len_out = DIV_ROUND(size, sectorsize);
+		*bitmap_len_out = DIV_ROUND(*bitmap_len_out, 8);
+
+		*data_offset_out = bitmap_offset + *bitmap_len_out;
+		*data_offset_out = ROUND_UP(*data_offset_out, align);
+	}
+}
+
+static int absolutize(char *to, int size, char *from)
+{
+	char save_cwd[256], *slash;
+	int remaining;
+
+	if (getcwd(save_cwd, sizeof(save_cwd)) == NULL) {
+		cow_printf("absolutize : unable to get cwd - errno = %d\n",
+			   errno);
+		return -1;
+	}
+	slash = strrchr(from, '/');
+	if (slash != NULL) {
+		*slash = '\0';
+		if (chdir(from)) {
+			*slash = '/';
+			cow_printf("absolutize : Can't cd to '%s' - "
+				   "errno = %d\n", from, errno);
+			return -1;
+		}
+		*slash = '/';
+		if (getcwd(to, size) == NULL) {
+			cow_printf("absolutize : unable to get cwd of '%s' - "
+			       "errno = %d\n", from, errno);
+			return -1;
+		}
+		remaining = size - strlen(to);
+		if (strlen(slash) + 1 > remaining) {
+			cow_printf("absolutize : unable to fit '%s' into %d "
+			       "chars\n", from, size);
+			return -1;
+		}
+		strcat(to, slash);
+	}
+	else {
+		if (strlen(save_cwd) + 1 + strlen(from) + 1 > size) {
+			cow_printf("absolutize : unable to fit '%s' into %d "
+			       "chars\n", from, size);
+			return -1;
+		}
+		strcpy(to, save_cwd);
+		strcat(to, "/");
+		strcat(to, from);
+	}
+	if (chdir(save_cwd)) {
+		cow_printf("absolutize : Can't cd to '%s' - "
+			   "errno = %d\n", save_cwd, errno);
+		return -1;
+	}
+	return 0;
+}
+
+int write_cow_header(char *cow_file, int fd, char *backing_file,
+		     int sectorsize, int alignment, unsigned long long *size)
+{
+	struct cow_header_v3 *header;
+	long long modtime;
+	int err;
+
+	err = cow_seek_file(fd, 0);
+	if (err < 0) {
+		cow_printf("write_cow_header - lseek failed, err = %d\n", -err);
+		goto out;
+	}
+
+	err = -ENOMEM;
+	header = cow_malloc(sizeof(*header));
+	if (header == NULL) {
+		cow_printf("write_cow_header - failed to allocate COW V3 "
+			   "header\n");
+		goto out;
+	}
+	header->magic = htobe32(COW_MAGIC);
+	header->version = htobe32(COW_VERSION);
+
+	err = -EINVAL;
+	if (strlen(backing_file) > sizeof(header->backing_file) - 1) {
+		/* Below, %zd is for a size_t value */
+		cow_printf("Backing file name \"%s\" is too long - names are "
+			   "limited to %zd characters\n", backing_file,
+			   sizeof(header->backing_file) - 1);
+		goto out_free;
+	}
+
+	if (absolutize(header->backing_file, sizeof(header->backing_file),
+		      backing_file))
+		goto out_free;
+
+	err = os_file_modtime(header->backing_file, &modtime);
+	if (err < 0) {
+		cow_printf("write_cow_header - backing file '%s' mtime "
+			   "request failed, err = %d\n", header->backing_file,
+			   -err);
+		goto out_free;
+	}
+
+	err = cow_file_size(header->backing_file, size);
+	if (err < 0) {
+		cow_printf("write_cow_header - couldn't get size of "
+			   "backing file '%s', err = %d\n",
+			   header->backing_file, -err);
+		goto out_free;
+	}
+
+	header->mtime = htobe32(modtime);
+	header->size = htobe64(*size);
+	header->sectorsize = htobe32(sectorsize);
+	header->alignment = htobe32(alignment);
+	header->cow_format = COW_BITMAP;
+
+	err = cow_write_file(fd, header, sizeof(*header));
+	if (err != sizeof(*header)) {
+		cow_printf("write_cow_header - write of header to "
+			   "new COW file '%s' failed, err = %d\n", cow_file,
+			   -err);
+		goto out_free;
+	}
+	err = 0;
+ out_free:
+	cow_free(header);
+ out:
+	return err;
+}
+
+int file_reader(__u64 offset, char *buf, int len, void *arg)
+{
+	int fd = *((int *) arg);
+
+	return pread(fd, buf, len, offset);
+}
+
+/* XXX Need to sanity-check the values read from the header */
+
+int read_cow_header(int (*reader)(__u64, char *, int, void *), void *arg,
+		    __u32 *version_out, char **backing_file_out,
+		    long long *mtime_out, unsigned long long *size_out,
+		    int *sectorsize_out, __u32 *align_out,
+		    int *bitmap_offset_out)
+{
+	union cow_header *header;
+	char *file;
+	int err, n;
+	unsigned long version, magic;
+
+	header = cow_malloc(sizeof(*header));
+	if (header == NULL) {
+	        cow_printf("read_cow_header - Failed to allocate header\n");
+		return -ENOMEM;
+	}
+	err = -EINVAL;
+	n = (*reader)(0, (char *) header, sizeof(*header), arg);
+	if (n < offsetof(typeof(header->v1), backing_file)) {
+		cow_printf("read_cow_header - short header\n");
+		goto out;
+	}
+
+	magic = header->v1.magic;
+	if (magic == COW_MAGIC)
+		version = header->v1.version;
+	else if (magic == be32toh(COW_MAGIC))
+		version = be32toh(header->v1.version);
+	/* No error printed because the non-COW case comes through here */
+	else goto out;
+
+	*version_out = version;
+
+	if (version == 1) {
+		if (n < sizeof(header->v1)) {
+			cow_printf("read_cow_header - failed to read V1 "
+				   "header\n");
+			goto out;
+		}
+		*mtime_out = header->v1.mtime;
+		*size_out = header->v1.size;
+		*sectorsize_out = header->v1.sectorsize;
+		*bitmap_offset_out = sizeof(header->v1);
+		*align_out = *sectorsize_out;
+		file = header->v1.backing_file;
+	}
+	else if (version == 2) {
+		if (n < sizeof(header->v2)) {
+			cow_printf("read_cow_header - failed to read V2 "
+				   "header\n");
+			goto out;
+		}
+		*mtime_out = be32toh(header->v2.mtime);
+		*size_out = be64toh(header->v2.size);
+		*sectorsize_out = be32toh(header->v2.sectorsize);
+		*bitmap_offset_out = sizeof(header->v2);
+		*align_out = *sectorsize_out;
+		file = header->v2.backing_file;
+	}
+	/* This is very subtle - see above at union cow_header definition */
+	else if (version == 3 && (*((int*)header->v3.backing_file) != 0)) {
+		if (n < sizeof(header->v3)) {
+			cow_printf("read_cow_header - failed to read V3 "
+				   "header\n");
+			goto out;
+		}
+		*mtime_out = be32toh(header->v3.mtime);
+		*size_out = be64toh(header->v3.size);
+		*sectorsize_out = be32toh(header->v3.sectorsize);
+		*align_out = be32toh(header->v3.alignment);
+		if (*align_out == 0) {
+			cow_printf("read_cow_header - invalid COW header, "
+				   "align == 0\n");
+		}
+		*bitmap_offset_out = ROUND_UP(sizeof(header->v3), *align_out);
+		file = header->v3.backing_file;
+	}
+	else if (version == 3) {
+		cow_printf("read_cow_header - broken V3 file with"
+			   " 64-bit layout - recovering content.\n");
+
+		if (n < sizeof(header->v3_b)) {
+			cow_printf("read_cow_header - failed to read V3 "
+				   "header\n");
+			goto out;
+		}
+
+		/*
+		 * this was used until Dec2005 - 64bits are needed to represent
+		 * 2106+. I.e. we can safely do this truncating cast.
+		 *
+		 * Additionally, we must use be32toh() instead of be64toh(), since
+		 * the program used to use the former (tested - I got mtime
+		 * mismatch "0 vs whatever").
+		 *
+		 * Ever heard about bug-to-bug-compatibility ? ;-) */
+		*mtime_out = (time32_t) be32toh(header->v3_b.mtime);
+
+		*size_out = be64toh(header->v3_b.size);
+		*sectorsize_out = be32toh(header->v3_b.sectorsize);
+		*align_out = be32toh(header->v3_b.alignment);
+		if (*align_out == 0) {
+			cow_printf("read_cow_header - invalid COW header, "
+				   "align == 0\n");
+		}
+		*bitmap_offset_out = ROUND_UP(sizeof(header->v3_b), *align_out);
+		file = header->v3_b.backing_file;
+	}
+	else {
+		cow_printf("read_cow_header - invalid COW version\n");
+		goto out;
+	}
+	err = -ENOMEM;
+	*backing_file_out = cow_strdup(file);
+	if (*backing_file_out == NULL) {
+		cow_printf("read_cow_header - failed to allocate backing "
+			   "file\n");
+		goto out;
+	}
+	err = 0;
+ out:
+	cow_free(header);
+	return err;
+}
+
+int init_cow_file(int fd, char *cow_file, char *backing_file, int sectorsize,
+		  int alignment, int *bitmap_offset_out,
+		  unsigned long *bitmap_len_out, int *data_offset_out)
+{
+	unsigned long long size, offset;
+	char zero = 0;
+	int err;
+
+	err = write_cow_header(cow_file, fd, backing_file, sectorsize,
+			       alignment, &size);
+	if (err)
+		goto out;
+
+	*bitmap_offset_out = ROUND_UP(sizeof(struct cow_header_v3), alignment);
+	cow_sizes(COW_VERSION, size, sectorsize, alignment, *bitmap_offset_out,
+		  bitmap_len_out, data_offset_out);
+
+	offset = *data_offset_out + size - sizeof(zero);
+	err = cow_seek_file(fd, offset);
+	if (err < 0) {
+		cow_printf("cow bitmap lseek failed : err = %d\n", -err);
+		goto out;
+	}
+
+	/*
+	 * does not really matter how much we write it is just to set EOF
+	 * this also sets the entire COW bitmap
+	 * to zero without having to allocate it
+	 */
+	err = cow_write_file(fd, &zero, sizeof(zero));
+	if (err != sizeof(zero)) {
+		cow_printf("Write of bitmap to new COW file '%s' failed, "
+			   "err = %d\n", cow_file, -err);
+		if (err >= 0)
+			err = -EINVAL;
+		goto out;
+	}
+
+	return 0;
+ out:
+	return err;
+}