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qcow.c
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qcow.c
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/*
* Copyright 2016, Red Hat, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may
* not use this file except in compliance with the License. You may obtain
* a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations
* under the License.
*/
/* Based on QEMU block/qcow{2}.c, which has this license: */
/*
* Block driver for the QCOW format
*
* Original driver from QEMU
* Copyright (c) 2004-2006 Fabrice Bellard
*
* Modified for tcmu-runner by Chris Leech
* Copyright (c) 2015, Red Hat, Inc.
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
#define _GNU_SOURCE
#include <stddef.h>
#include <stdint.h>
#include <stdbool.h>
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <fcntl.h>
#include <endian.h>
#include <limits.h>
#include <inttypes.h>
#include <libgen.h>
#include <alloca.h>
#include <sys/stat.h>
#include <sys/uio.h>
#include <scsi/scsi.h>
#include <assert.h>
#include <errno.h>
#include <zlib.h>
#if defined(HAVE_LINUX_FALLOC)
#include <linux/falloc.h>
#endif
#include "tcmu-runner.h"
#include "scsi_defs.h"
#include "qcow.h"
#include "qcow2.h"
/* Block Device abstraction to support multiple image types */
struct bdev_ops;
static struct bdev_ops qcow_ops;
static struct bdev_ops qcow2_ops;
static struct bdev_ops raw_ops;
struct bdev {
char *config;
void *private;
struct bdev_ops *ops;
/* from TCMU configfs configuration */
int64_t size;
uint32_t block_size;
int fd; /* image file descriptor */
};
struct bdev_ops {
int (*probe) (struct bdev *dev, int dirfd, const char *pathname);
int (*open) (struct bdev *dev, int dirfd, const char *pathname, int flags);
void (*close) (struct bdev *dev);
ssize_t (*preadv) (struct bdev *bdev, struct iovec *iov, int iovcnt, off_t offset);
ssize_t (*pwritev) (struct bdev *bdev, struct iovec *iov, int iovcnt, off_t offset);
};
static int bdev_open(struct bdev *bdev, int dirfd, const char *pathname, int flags)
{
struct bdev_ops *bdev_ops[] = {
&qcow_ops,
&qcow2_ops,
&raw_ops,
NULL,
};
struct bdev_ops **ops;
for (ops = &bdev_ops[0]; *ops != NULL; ops++) {
if ((*ops)->probe(bdev, dirfd, pathname) == 0) {
if ((*ops)->open(bdev, dirfd, pathname, flags) == -1) {
tcmu_err("image open failed: %s\n", pathname);
goto err;
}
bdev->ops = *ops;
return 0;
}
}
tcmu_err("image format not recognized: %s\n", pathname);
err:
return -1;
}
static int get_dirfd(int fd)
{
char proc_path[64];
char *img_path;
char *dir;
int dirfd;
ssize_t len;
/* more than enough room for "/proc/self/fd/<INT_MAX>\0" */
snprintf(proc_path, 64, "/proc/self/fd/%d", fd);
/* can't use lstat in /proc to get name length :( */
img_path = malloc(PATH_MAX);
len = readlink(proc_path, img_path, PATH_MAX);
img_path[len] = '\0';
dir = dirname(img_path);
dirfd = open(dir, O_DIRECTORY | O_PATH);
free(img_path);
return dirfd;
}
/* QCOW version 1 */
static void qcow_header_bswap(struct qcow_header *be, struct qcow_header *dst)
{
dst->magic = be32toh(be->magic);
dst->version = be32toh(be->version);
dst->backing_file_offset = be64toh(be->backing_file_offset);
dst->backing_file_size = be32toh(be->backing_file_size);
dst->mtime = be32toh(be->mtime);
dst->size = be64toh(be->size);
dst->cluster_bits = be->cluster_bits;
dst->l2_bits = be->l2_bits;
dst->padding = be16toh(be->padding);
dst->crypt_method = be32toh(be->crypt_method);
dst->l1_table_offset = be64toh(be->l1_table_offset);
}
static void qcow2_header_bswap(struct qcow2_header *be, struct qcow2_header *dst)
{
dst->magic = be32toh(be->magic);
dst->version = be32toh(be->version);
dst->backing_file_offset = be64toh(be->backing_file_offset);
dst->backing_file_size = be32toh(be->backing_file_size);
dst->cluster_bits = be32toh(be->cluster_bits);
dst->size = be64toh(be->size) /* in bytes */;
dst->crypt_method = be32toh(be->crypt_method);
dst->l1_size = be32toh(be->l1_size);
dst->l1_table_offset = be64toh(be->l1_table_offset);
dst->refcount_table_offset = be64toh(be->refcount_table_offset);
dst->refcount_table_clusters = be32toh(be->refcount_table_clusters);
dst->nb_snapshots = be32toh(be->nb_snapshots);
dst->snapshots_offset = be64toh(be->snapshots_offset);
if (dst->version == 2) {
/* The following fields are only valid for version >= 3 */
dst->incompatible_features = 0;
dst->compatible_features = 0;
dst->autoclear_features = 0;
dst->refcount_order = 4;
dst->header_length = 72;
} else {
dst->incompatible_features = be64toh(be->incompatible_features);
dst->compatible_features = be64toh(be->compatible_features);
dst->autoclear_features = be64toh(be->autoclear_features);
dst->refcount_order = be32toh(be->refcount_order);
dst->header_length = be32toh(be->header_length);
}
}
#define RC_CACHE_SIZE L2_CACHE_SIZE
struct qcow_state
{
int fd;
uint64_t size;
unsigned int cluster_bits;
unsigned int cluster_size;
unsigned int cluster_sectors;
unsigned int l2_bits;
unsigned int l2_size;
uint64_t cluster_offset_mask;
/* L1 table, load entire thing into RAM */
unsigned int l1_size;
uint64_t l1_table_offset;
uint64_t *l1_table;
/* L2 cache */
uint64_t *l2_cache;
uint64_t l2_cache_offsets[L2_CACHE_SIZE];
int l2_cache_counts[L2_CACHE_SIZE];
/* cluster decompression cache */
uint8_t *cluster_cache;
uint8_t *cluster_data;
uint64_t cluster_cache_offset;
struct bdev *backing_image;
uint64_t cluster_compressed;
uint64_t cluster_copied;
uint64_t cluster_mask;
/* qcow2 refcount top level table */
uint64_t refcount_table_offset;
uint32_t refcount_table_size;
uint64_t *refcount_table;
/* refcount block cache */
unsigned int refcount_order;
void *rc_cache;
uint64_t rc_cache_offsets[RC_CACHE_SIZE];
int rc_cache_counts[RC_CACHE_SIZE];
uint64_t (*block_alloc) (struct qcow_state *s, size_t size);
int (*set_refcount) (struct qcow_state *s, uint64_t cluster_offset, uint64_t value);
uint64_t first_free_cluster;
};
static uint64_t qcow_block_alloc(struct qcow_state *s, size_t size);
static uint64_t qcow2_block_alloc(struct qcow_state *s, size_t size);
static int qcow_no_refcount(struct qcow_state *s, uint64_t cluster_offset, uint64_t value)
{
return 0;
}
static int qcow2_set_refcount(struct qcow_state *s, uint64_t cluster_offset, uint64_t value);
static int qcow_probe(struct bdev *bdev, int dirfd, const char *pathname)
{
int fd;
struct {
uint32_t magic;
uint32_t version;
} head;
tcmu_dbg("%s\n", __func__);
if (faccessat(dirfd, pathname, R_OK|W_OK, AT_EACCESS) == -1)
return -1;
if ((fd = openat(dirfd, pathname, O_RDONLY)) == -1)
return -1;
if (pread(fd, &head, sizeof(head), 0) == -1)
goto err;
if (be32toh(head.magic) != QCOW_MAGIC)
goto err;
if (be32toh(head.version) != 1)
goto err;
close(fd);
return 0;
err:
close(fd);
return -1;
}
static int qcow2_probe(struct bdev *bdev, int dirfd, const char *pathname)
{
int fd;
struct {
uint32_t magic;
uint32_t version;
} head;
tcmu_dbg("%s\n", __func__);
if (faccessat(dirfd, pathname, R_OK|W_OK, AT_EACCESS) == -1) {
tcmu_err("faccessat failed dirfd %d, pathname %s, errno %d\n",
dirfd, pathname, errno);
return -1;
}
if ((fd = openat(dirfd, pathname, O_RDONLY)) == -1) {
tcmu_err("openat failed dirfd %d, pathname %s, errno %d\n",
dirfd, pathname, errno);
return -1;
}
if (pread(fd, &head, sizeof(head), 0) == -1) {
tcmu_err("pread failed dirfd %d, pathname %s, errno %d\n",
dirfd, pathname, errno);
goto err;
}
if (be32toh(head.magic) != QCOW_MAGIC) {
tcmu_warn("not qcow: will treat as raw: %s", pathname);
goto err;
}
if (be32toh(head.version) < 2) {
tcmu_err("version = %d, pathname %s\n", head.version, pathname);
goto err;
}
close(fd);
return 0;
err:
close(fd);
return -1;
}
static int qcow_validate_header(struct qcow_header *header)
{
if (header->magic != QCOW_MAGIC) {
tcmu_err("header is not QCOW\n");
return -1;
}
if (header->version != 1) {
tcmu_err("version is %d, expected 1\n", header->version);
return -1;
}
if (header->cluster_bits < 9 || header->cluster_bits > 16) {
tcmu_err("bad cluster_bits = %d\n", header->cluster_bits);
return -1;
}
if (header->l2_bits < (9 - 3) || header->l2_bits > (16 - 3)) {
tcmu_err("bad l2_bits = %d\n", header->l2_bits);
return -1;
}
switch (header->crypt_method) {
case QCOW_CRYPT_NONE:
break;
case QCOW_CRYPT_AES:
tcmu_err("QCOW AES-CBC encryption has been deprecated\n");
tcmu_err("Convert to unencrypted image using qemu-img\n");
return -1;
default:
tcmu_err("Invalid encryption value %d\n", header->crypt_method);
return -1;
}
return 0;
}
static int qcow2_validate_header(struct qcow2_header *header)
{
/* TODO check other stuff ... L1, refcount, snapshots */
if (header->magic != QCOW_MAGIC) {
tcmu_err("header is not QCOW\n");
return -1;
}
if (header->version < 2) {
tcmu_err("version is %d, expected 2 or 3\n", header->version);
return -1;
}
if (header->cluster_bits < 9 || header->cluster_bits > 16) {
tcmu_err("bad cluster_bits = %d\n", header->cluster_bits);
return -1;
}
switch (header->crypt_method) {
case QCOW2_CRYPT_NONE:
break;
case QCOW2_CRYPT_AES:
tcmu_err("QCOW AES-CBC encryption has been deprecated\n");
tcmu_err("Convert to unencrypted image using qemu-img\n");
return -1;
default:
tcmu_err("Invalid encryption value %d\n", header->crypt_method);
return -1;
}
return 0;
}
static int qcow_setup_backing_file(struct bdev *bdev, struct qcow_header *header)
{
struct qcow_state *s = bdev->private;
char *backing_file;
uint64_t offset;
size_t len;
int dirfd;
int ret;
offset = header->backing_file_offset;
len = header->backing_file_size;
if (offset == 0 || len == 0)
return 0;
if (len >= PATH_MAX) {
tcmu_err("Backing file name too long\n");
return -1;
}
backing_file = alloca(len + 1);
if (pread(bdev->fd, backing_file, len, header->backing_file_offset) != len) {
tcmu_err("Error reading backing file name\n");
return -1;
}
backing_file[len] = '\0';
s->backing_image = calloc(1, sizeof(struct bdev));
if (!s->backing_image)
return -1;
/* backing file settings copied from overlay */
s->backing_image->size = bdev->size;
s->backing_image->block_size = bdev->block_size;
/* backing file pathname may be relative to the overlay image */
dirfd = get_dirfd(bdev->fd);
if (dirfd == -1)
goto fail;
ret = bdev_open(s->backing_image, dirfd, backing_file, O_RDONLY);
close(dirfd);
if (ret == -1)
goto fail;
return 0;
fail:
free(s->backing_image);
s->backing_image = NULL;
return -1;
}
static int qcow2_setup_backing_file(struct bdev *bdev, struct qcow2_header *header)
{
/* backing file info is at the same place in both headers,
* so we can cheat and use this for qcow2 also */
return qcow_setup_backing_file(bdev, (struct qcow_header *) header);
}
static int qcow_image_open(struct bdev *bdev, int dirfd, const char *pathname, int flags)
{
struct qcow_header buf;
struct qcow_header header;
struct qcow_state *s;
uint64_t l1_size;
unsigned int shift;
ssize_t read;
s = calloc(1, sizeof(struct qcow_state));
if (!s)
return -1;
bdev->private = s;
bdev->fd = openat(dirfd, pathname, flags);
s->fd = bdev->fd;
if (bdev->fd == -1) {
tcmu_err("Failed to open file: %s\n", pathname);
goto fail_nofd;
}
if (pread(bdev->fd, &buf, sizeof(buf), 0) != sizeof(buf)) {
tcmu_err("Failed to read file: &s\n", pathname);
goto fail;
}
qcow_header_bswap(&buf, &header);
if (qcow_validate_header(&header) < 0)
goto fail;
if (bdev->size != header.size) {
tcmu_err("size misconfigured, TCMU says %" PRId64
" but image says %" PRId64 "\n",
bdev->size, header.size);
goto fail;
}
s->size = bdev->size;
if (bdev->block_size != 512) {
tcmu_err("block_size misconfigured, TCMU says %" PRId32
" but qcow only supports 512\n",
bdev->block_size);
goto fail;
}
s->cluster_bits = header.cluster_bits;
s->cluster_size = 1 << s->cluster_bits;
s->cluster_sectors = 1 << (s->cluster_bits - 9);
s->l2_bits = header.l2_bits;
s->l2_size = 1 << s->l2_bits;
s->cluster_offset_mask = (1LL << (63 - s->cluster_bits)) - 1;
shift = s->cluster_bits + s->l2_bits;
if (header.size > UINT64_MAX - (1LL << shift)) {
tcmu_err("Image size too big\n");
goto fail;
}
l1_size = (header.size + (1LL << shift) - 1) >> shift;
if (l1_size > INT_MAX / sizeof(uint64_t)) {
tcmu_err("Image size too big\n");
goto fail;
}
s->l1_size = l1_size;
s->l1_table_offset = header.l1_table_offset;
s->l1_table = calloc(s->l1_size, sizeof(uint64_t));
if (!s->l1_table) {
tcmu_err("Failed to allocate L1 table\n");
goto fail;
}
read = pread(bdev->fd, s->l1_table, s->l1_size * sizeof(uint64_t), s->l1_table_offset);
if (read != s->l1_size * sizeof(uint64_t)) {
tcmu_err("Failed to read L1 table\n");
goto fail;
}
s->l2_cache = calloc(L2_CACHE_SIZE, s->l2_size * sizeof(uint64_t));
if (s->l2_cache == NULL) {
tcmu_err("Failed to allocate L2 cache\n");
goto fail;
}
/* cluster decompression cache */
s->cluster_cache = calloc(1, s->cluster_size);
s->cluster_data = calloc(1, s->cluster_size);
s->cluster_cache_offset = -1;
if (!s->cluster_cache || !s->cluster_data) {
tcmu_err("Failed to allocate cluster decompression space\n");
goto fail;
}
if (qcow_setup_backing_file(bdev, &header) == -1)
goto fail;
s->cluster_compressed = QCOW_OFLAG_COMPRESSED;
s->cluster_mask = ~QCOW_OFLAG_COMPRESSED;
s->block_alloc = qcow_block_alloc;
s->set_refcount = qcow_no_refcount;
tcmu_dbg("%d: %s\n", bdev->fd, pathname);
return 0;
fail:
close(bdev->fd);
free(s->cluster_cache);
free(s->cluster_data);
free(s->l2_cache);
free(s->l1_table);
fail_nofd:
free(s);
return -1;
}
static int qcow2_image_open(struct bdev *bdev, int dirfd, const char *pathname, int flags)
{
struct qcow2_header buf;
struct qcow2_header header;
struct qcow_state *s;
uint64_t l1_size;
unsigned int shift;
ssize_t read;
s = calloc(1, sizeof(struct qcow_state));
if (!s)
return -1;
bdev->private = s;
bdev->fd = openat(dirfd, pathname, flags);
s->fd = bdev->fd;
if (bdev->fd == -1) {
tcmu_err("Failed to open file: %s\n", pathname);
goto fail_nofd;
}
if (pread(bdev->fd, &buf, sizeof(buf), 0) != sizeof(buf)) {
tcmu_err("Failed to read file: %s\n", pathname);
goto fail;
}
qcow2_header_bswap(&buf, &header);
if (qcow2_validate_header(&header) < 0)
goto fail;
if (bdev->size != header.size) {
tcmu_err("size misconfigured, TCMU says %" PRId64
" but image says %" PRId64 "\n",
bdev->size, header.size);
goto fail;
}
s->size = bdev->size;
if (bdev->block_size != 512) {
tcmu_err("block_size misconfigured, TCMU says %" PRId32
" but qcow only supports 512\n",
bdev->block_size);
goto fail;
}
s->cluster_bits = header.cluster_bits;
s->cluster_size = 1 << s->cluster_bits;
s->cluster_sectors = 1 << (s->cluster_bits - 9);
s->l2_bits = s->cluster_bits - 3; // L2 table is always 1 cluster in size (8 (2^3) byte entries)
s->l2_size = 1 << s->l2_bits;
s->cluster_offset_mask = (1LL << (63 - s->cluster_bits)) - 1;
shift = s->cluster_bits + s->l2_bits;
if (header.size > UINT64_MAX - (1LL << shift)) {
tcmu_err("Image size too big\n");
goto fail;
}
l1_size = (header.size + (1LL << shift) - 1) >> shift;
if (l1_size > INT_MAX / sizeof(uint64_t)) {
tcmu_err("Image size too big\n");
goto fail;
}
s->l1_size = l1_size;
// why did they add this to qcow2 ?
if (header.l1_size != s->l1_size) {
tcmu_err("L1 size is incorrect\n");
goto fail;
}
s->l1_table_offset = header.l1_table_offset;
s->l1_table = calloc(s->l1_size, sizeof(uint64_t));
if (!s->l1_table) {
tcmu_err("Failed to allocate L1 table\n");
goto fail;
}
read = pread(bdev->fd, s->l1_table, s->l1_size * sizeof(uint64_t), s->l1_table_offset);
if (read != s->l1_size * sizeof(uint64_t)) {
tcmu_err("Failed to read L1 table\n");
goto fail;
}
s->l2_cache = calloc(L2_CACHE_SIZE, s->l2_size * sizeof(uint64_t));
if (s->l2_cache == NULL) {
tcmu_err("Failed to allocate L2 cache\n");
goto fail;
}
tcmu_dbg("s->l2_cache = %p\n", s->l2_cache);
/* cluster decompression cache */
s->cluster_cache = calloc(1, s->cluster_size);
s->cluster_data = calloc(1, s->cluster_size);
s->cluster_cache_offset = -1;
if (!s->cluster_cache || !s->cluster_data) {
tcmu_err("Failed to allocate cluster decompression space\n");
goto fail;
}
tcmu_dbg("s->cluster_cache = %p\n", s->cluster_cache);
/* refcount table */
s->refcount_table_offset = header.refcount_table_offset;
s->refcount_table_size = header.refcount_table_clusters << (s->cluster_bits - 3);
s->refcount_table = calloc(s->refcount_table_size, sizeof(uint64_t));
if (!s->refcount_table) {
tcmu_err("Failed to allocate refcount table\n");
goto fail;
}
read = pread(bdev->fd, s->refcount_table, s->refcount_table_size * sizeof(uint64_t), s->refcount_table_offset);
if (read != s->refcount_table_size * sizeof(uint64_t)) {
tcmu_err("Failed to read refcount table\n");
goto fail;
}
s->refcount_order = header.refcount_order;
s->rc_cache = calloc(RC_CACHE_SIZE, s->cluster_size);
if (s->rc_cache == NULL) {
tcmu_err("Failed to allocate refcount cache\n");
goto fail;
}
tcmu_dbg("s->rc_cache = %p\n", s->rc_cache);
if (qcow2_setup_backing_file(bdev, &header) == -1)
goto fail;
s->cluster_compressed = QCOW2_OFLAG_COMPRESSED;
s->cluster_copied = QCOW2_OFLAG_COPIED;
s->cluster_mask = ~(QCOW_OFLAG_COMPRESSED | QCOW2_OFLAG_COPIED | QCOW2_OFLAG_ZERO);
s->block_alloc = qcow2_block_alloc;
s->set_refcount = qcow2_set_refcount;
tcmu_dbg("%d: %s\n", bdev->fd, pathname);
return 0;
fail:
close(bdev->fd);
free(s->cluster_cache);
free(s->cluster_data);
free(s->rc_cache);
free(s->refcount_table);
free(s->l2_cache);
free(s->l1_table);
fail_nofd:
free(s);
return -1;
}
static void qcow_image_close(struct bdev *bdev)
{
struct qcow_state *s = bdev->private;
if (s->backing_image) {
s->backing_image->ops->close(s->backing_image);
free(s->backing_image);
}
close(bdev->fd);
free(s->cluster_cache);
free(s->cluster_data);
free(s->l1_table);
free(s->l2_cache);
free(s->refcount_table);
free(s->rc_cache);
free(s);
}
static uint64_t *l2_cache_lookup(struct qcow_state *s, uint64_t l2_offset)
{
int i, j;
int min_index = 0;
int min_count = INT_MAX;
uint64_t *l2_table;
ssize_t read;
/* l2 cache lookup */
for (i = 0; i < L2_CACHE_SIZE; i++) {
if (l2_offset == s->l2_cache_offsets[i]) {
if (++s->l2_cache_counts[i] == INT_MAX) {
for (j = 0; i < L2_CACHE_SIZE; j++) {
s->l2_cache_counts[j] >>= 1;
}
}
l2_table = s->l2_cache + (i << s->l2_bits);
tcmu_dbg("%s: l2 hit %llx at index %d\n", __func__, l2_table, i);
return l2_table;
}
}
/* not found, evict least used entry */
for (i = 0; i < L2_CACHE_SIZE; i++) {
if (s->l2_cache_counts[i] < min_count) {
min_count = s->l2_cache_counts[i];
min_index = i;
}
}
l2_table = s->l2_cache + (min_index << s->l2_bits);
read = pread(s->fd, l2_table, s->l2_size * sizeof(uint64_t), l2_offset);
if (read != s->l2_size * sizeof(uint64_t))
return NULL;
s->l2_cache_offsets[min_index] = l2_offset;
s->l2_cache_counts[min_index] = 1;
return l2_table;
}
static uint64_t qcow_cluster_alloc(struct qcow_state *s)
{
tcmu_dbg("%s\n", __func__);
return s->block_alloc(s, s->cluster_size);
}
/* qcow 1 simply grows the file as new clusters or L2 blocks are needed */
static uint64_t qcow_block_alloc(struct qcow_state *s, size_t size)
{
uint64_t offset;
off_t off;
off = lseek(s->fd, 0, SEEK_END);
if (off == -1)
return 0;
offset = (off + size - 1) & ~(size - 1);
if (ftruncate(s->fd, offset + size) == -1)
return 0;
return offset;
}
static uint64_t l2_table_alloc(struct qcow_state *s)
{
tcmu_dbg("%s\n", __func__);
return s->block_alloc(s, s->l2_size * sizeof(uint64_t));
}
static int l1_table_update(struct qcow_state *s, unsigned int l1_index, uint64_t l2_offset)
{
ssize_t ret;
tcmu_dbg("%s: setting L1[%d] to %llx\n", __func__, l1_index, l2_offset);
s->l1_table[l1_index] = htobe64(l2_offset);
ret = pwrite(s->fd,
&s->l1_table[l1_index],
sizeof(uint64_t),
s->l1_table_offset + (l1_index * sizeof(uint64_t)));
if (ret != sizeof(uint64_t))
tcmu_err("%s: error, L1 writeback failed (%zd)\n", __func__, ret);
fdatasync(s->fd);
return ret;
}
/* refcount table */
static uint64_t get_refcount(unsigned int order, void *rcblock, size_t index)
{
switch (order) {
case 0:
return (((uint8_t *)rcblock)[index / 8] >> (index % 8)) & 0x1;
case 1:
return (((uint8_t *)rcblock)[index / 4] >> (2 * (index % 4))) & 0x3;
case 2:
return (((uint8_t *)rcblock)[index / 2] >> (4 * (index % 2))) & 0xf;
case 3:
return ((uint8_t *)rcblock)[index];
case 4:
return be16toh(((uint16_t *)rcblock)[index]);
case 5:
return be32toh(((uint32_t *)rcblock)[index]);
case 6:
return be64toh(((uint64_t *)rcblock)[index]);
default:
assert(0);
}
return 0; /* NOT REACHED */
}
static void set_refcount(unsigned int order, void *rcblock, size_t index, uint64_t value)
{
assert(!(value >> (1 << order)));
switch (order) {
case 0:
((uint8_t *)rcblock)[index / 8] &= ~(0x1 << (index % 8));
((uint8_t *)rcblock)[index / 8] |= value << (index % 8);
break;
case 1:
((uint8_t *)rcblock)[index / 4] &= ~(0x3 << (2 * (index % 4)));
((uint8_t *)rcblock)[index / 4] |= value << (2 * (index % 4));
break;
case 2:
((uint8_t *)rcblock)[index / 2] &= ~(0xf << (4 * (index % 2)));
((uint8_t *)rcblock)[index / 2] |= value << (4 * (index % 2));
break;
case 3:
((uint8_t *)rcblock)[index] = value;
break;
case 4:
((uint16_t *)rcblock)[index] = htobe16(value);
break;
case 5:
((uint32_t *)rcblock)[index] = htobe32(value);
break;
case 6:
((uint64_t *)rcblock)[index] = htobe64(value);
break;
default:
assert(0);
}
}
static void *rc_cache_lookup(struct qcow_state *s, uint64_t rc_offset)
{
int i, j;
int min_index = 0;
int min_count = INT_MAX;
void *rc_table;
ssize_t read;
/* rc cache lookup */
for (i = 0; i < RC_CACHE_SIZE; i++) {
if (rc_offset == s->rc_cache_offsets[i]) {
if (++s->rc_cache_counts[i] == INT_MAX) {
for (j = 0; i < RC_CACHE_SIZE; j++) {
s->rc_cache_counts[j] >>= 1;
}
}
rc_table = s->rc_cache + (i << s->cluster_bits);
return rc_table;
}
}
/* not found, evict least used entry */
for (i = 0; i < RC_CACHE_SIZE; i++) {
if (s->rc_cache_counts[i] < min_count) {
min_count = s->rc_cache_counts[i];
min_index = i;
}
}
rc_table = s->rc_cache + (min_index << s->cluster_bits);
read = pread(s->fd, rc_table, 1 << s->cluster_bits, rc_offset);
if (read != 1 << s->cluster_bits)
return NULL;
s->rc_cache_offsets[min_index] = rc_offset;
s->rc_cache_counts[min_index] = 1;
return rc_table;
}
static uint64_t qcow2_get_refcount(struct qcow_state *s, int64_t cluster_offset)
{
unsigned int refcount_bits;
uint64_t rc_index;
uint64_t refblock_offset;
uint64_t refblock_index;
void *refblock;
uint64_t rc;
refcount_bits = s->cluster_bits - s->refcount_order + 3;
rc_index = cluster_offset >> (s->cluster_bits + refcount_bits);
refblock_offset = be64toh(s->refcount_table[rc_index]);
if (!refblock_offset)
return 0;
refblock = rc_cache_lookup(s, refblock_offset);
if (!refblock)
return 0;
refblock_index = (cluster_offset >> s->cluster_bits) & ((1 << refcount_bits) - 1);
rc = get_refcount(s->refcount_order, refblock, refblock_index);
return rc;
}
static int rc_table_update(struct qcow_state *s, unsigned int rc_index, uint64_t refblock_offset)
{
ssize_t ret;
tcmu_dbg("%s: setting RC[%d] to %llx\n", __func__, rc_index, refblock_offset);
s->refcount_table[rc_index] = htobe64(refblock_offset);
ret = pwrite(s->fd,
&s->refcount_table[rc_index],
sizeof(uint64_t),
s->refcount_table_offset + (rc_index * sizeof(uint64_t)));
if (ret != sizeof(uint64_t))
tcmu_err("%s: error, RC writeback failed (%zd)\n", __func__, ret);
fdatasync(s->fd);
return ret;
}
static int qcow2_set_refcount(struct qcow_state *s, uint64_t cluster_offset, uint64_t value)
{
unsigned int refcount_bits;
uint64_t rc_index;
uint64_t refblock_offset;
uint64_t refblock_index;
void *refblock;
ssize_t ret;
refcount_bits = s->cluster_bits - s->refcount_order + 3;
rc_index = cluster_offset >> (s->cluster_bits + refcount_bits);
refblock_offset = be64toh(s->refcount_table[rc_index]);
refblock_index = (cluster_offset >> s->cluster_bits) & ((1 << refcount_bits) - 1);
tcmu_dbg("%s: rc[%d][%d] = %llx[%d] = %d\n", __func__, rc_index, refblock_index, refblock_offset, refblock_index, value);
if (!refblock_offset) {
if (!(refblock_offset = qcow_cluster_alloc(s))) {
tcmu_err("refblock allocation failure\n");
return -1;
}
rc_table_update(s, rc_index, refblock_offset | s->cluster_copied);
qcow2_set_refcount(s, refblock_offset, 1);
}
refblock = rc_cache_lookup(s, refblock_offset);
if (!refblock) {
tcmu_err("refblock cache failure\n");
return -1;
}
set_refcount(s->refcount_order, refblock, refblock_index, value);
/* for now this writes back the entire block */
ret = pwrite(s->fd, refblock, s->cluster_size, refblock_offset);
if (ret != s->cluster_size)
tcmu_err("%s: error, refblock writeback failed (%zd)\n", __func__, ret);
fdatasync(s->fd);
return ret;
}
/* qcow 2 uses the refcount table to find free clusters */
static uint64_t qcow2_block_alloc(struct qcow_state *s, size_t size)
{
uint64_t cluster;
uint64_t count;
int ret;
tcmu_dbg(" %s %zx\n", __func__, size);
/* all allocations for qcow2 should be of the same size */
assert(size == s->cluster_size);
for (cluster = s->first_free_cluster; cluster < s->size; cluster += s->cluster_size) {
count = qcow2_get_refcount(s, cluster);
if (count == 0) {
ret = fallocate(s->fd, FALLOC_FL_ZERO_RANGE, cluster, s->cluster_size);
if (ret) {
tcmu_err("fallocate failed: %m\n");
return 0;
}