auto import from //depot/cupcake/@135843

1 files changed, 267 insertions, 0 deletions

diff --git a/block-cow.c b/block-cow.c
new file mode 100644
index 0000000..9e7b646
--- /dev/null
+++ b/block-cow.c
@@ -0,0 +1,267 @@
+/*
+ * Block driver for the COW format
+ *
+ * Copyright (c) 2004 Fabrice Bellard
+ *
+ * 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.
+ */
+#ifndef _WIN32
+#include "qemu-common.h"
+#include "block_int.h"
+#include <sys/mman.h>
+
+/**************************************************************/
+/* COW block driver using file system holes */
+
+/* user mode linux compatible COW file */
+#define COW_MAGIC 0x4f4f4f4d  /* MOOO */
+#define COW_VERSION 2
+
+struct cow_header_v2 {
+    uint32_t magic;
+    uint32_t version;
+    char backing_file[1024];
+    int32_t mtime;
+    uint64_t size;
+    uint32_t sectorsize;
+};
+
+typedef struct BDRVCowState {
+    int fd;
+    uint8_t *cow_bitmap; /* if non NULL, COW mappings are used first */
+    uint8_t *cow_bitmap_addr; /* mmap address of cow_bitmap */
+    int cow_bitmap_size;
+    int64_t cow_sectors_offset;
+} BDRVCowState;
+
+static int cow_probe(const uint8_t *buf, int buf_size, const char *filename)
+{
+    const struct cow_header_v2 *cow_header = (const void *)buf;
+
+    if (buf_size >= sizeof(struct cow_header_v2) &&
+        be32_to_cpu(cow_header->magic) == COW_MAGIC &&
+        be32_to_cpu(cow_header->version) == COW_VERSION)
+        return 100;
+    else
+        return 0;
+}
+
+static int cow_open(BlockDriverState *bs, const char *filename, int flags)
+{
+    BDRVCowState *s = bs->opaque;
+    int fd;
+    struct cow_header_v2 cow_header;
+    int64_t size;
+
+    fd = open(filename, O_RDWR | O_BINARY | O_LARGEFILE);
+    if (fd < 0) {
+        fd = open(filename, O_RDONLY | O_BINARY | O_LARGEFILE);
+        if (fd < 0)
+            return -1;
+    }
+    s->fd = fd;
+    /* see if it is a cow image */
+    if (read(fd, &cow_header, sizeof(cow_header)) != sizeof(cow_header)) {
+        goto fail;
+    }
+
+    if (be32_to_cpu(cow_header.magic) != COW_MAGIC ||
+        be32_to_cpu(cow_header.version) != COW_VERSION) {
+        goto fail;
+    }
+
+    /* cow image found */
+    size = be64_to_cpu(cow_header.size);
+    bs->total_sectors = size / 512;
+
+    pstrcpy(bs->backing_file, sizeof(bs->backing_file),
+            cow_header.backing_file);
+
+    /* mmap the bitmap */
+    s->cow_bitmap_size = ((bs->total_sectors + 7) >> 3) + sizeof(cow_header);
+    s->cow_bitmap_addr = mmap(get_mmap_addr(s->cow_bitmap_size),
+                              s->cow_bitmap_size,
+                              PROT_READ | PROT_WRITE,
+                              MAP_SHARED, s->fd, 0);
+    if (s->cow_bitmap_addr == MAP_FAILED)
+        goto fail;
+    s->cow_bitmap = s->cow_bitmap_addr + sizeof(cow_header);
+    s->cow_sectors_offset = (s->cow_bitmap_size + 511) & ~511;
+    return 0;
+ fail:
+    close(fd);
+    return -1;
+}
+
+static inline void cow_set_bit(uint8_t *bitmap, int64_t bitnum)
+{
+    bitmap[bitnum / 8] |= (1 << (bitnum%8));
+}
+
+static inline int is_bit_set(const uint8_t *bitmap, int64_t bitnum)
+{
+    return !!(bitmap[bitnum / 8] & (1 << (bitnum%8)));
+}
+
+
+/* Return true if first block has been changed (ie. current version is
+ * in COW file).  Set the number of continuous blocks for which that
+ * is true. */
+static inline int is_changed(uint8_t *bitmap,
+                             int64_t sector_num, int nb_sectors,
+                             int *num_same)
+{
+    int changed;
+
+    if (!bitmap || nb_sectors == 0) {
+	*num_same = nb_sectors;
+	return 0;
+    }
+
+    changed = is_bit_set(bitmap, sector_num);
+    for (*num_same = 1; *num_same < nb_sectors; (*num_same)++) {
+	if (is_bit_set(bitmap, sector_num + *num_same) != changed)
+	    break;
+    }
+
+    return changed;
+}
+
+static int cow_is_allocated(BlockDriverState *bs, int64_t sector_num,
+                            int nb_sectors, int *pnum)
+{
+    BDRVCowState *s = bs->opaque;
+    return is_changed(s->cow_bitmap, sector_num, nb_sectors, pnum);
+}
+
+static int cow_read(BlockDriverState *bs, int64_t sector_num,
+                    uint8_t *buf, int nb_sectors)
+{
+    BDRVCowState *s = bs->opaque;
+    int ret, n;
+
+    while (nb_sectors > 0) {
+        if (is_changed(s->cow_bitmap, sector_num, nb_sectors, &n)) {
+            lseek(s->fd, s->cow_sectors_offset + sector_num * 512, SEEK_SET);
+            ret = read(s->fd, buf, n * 512);
+            if (ret != n * 512)
+                return -1;
+        } else {
+            if (bs->backing_hd) {
+                /* read from the base image */
+                ret = bdrv_read(bs->backing_hd, sector_num, buf, n);
+                if (ret < 0)
+                    return -1;
+            } else {
+            memset(buf, 0, n * 512);
+        }
+        }
+        nb_sectors -= n;
+        sector_num += n;
+        buf += n * 512;
+    }
+    return 0;
+}
+
+static int cow_write(BlockDriverState *bs, int64_t sector_num,
+                     const uint8_t *buf, int nb_sectors)
+{
+    BDRVCowState *s = bs->opaque;
+    int ret, i;
+
+    lseek(s->fd, s->cow_sectors_offset + sector_num * 512, SEEK_SET);
+    ret = write(s->fd, buf, nb_sectors * 512);
+    if (ret != nb_sectors * 512)
+        return -1;
+    for (i = 0; i < nb_sectors; i++)
+        cow_set_bit(s->cow_bitmap, sector_num + i);
+    return 0;
+}
+
+static void cow_close(BlockDriverState *bs)
+{
+    BDRVCowState *s = bs->opaque;
+    munmap(s->cow_bitmap_addr, s->cow_bitmap_size);
+    close(s->fd);
+}
+
+static int cow_create(const char *filename, int64_t image_sectors,
+                      const char *image_filename, int flags)
+{
+    int fd, cow_fd;
+    struct cow_header_v2 cow_header;
+    struct stat st;
+
+    if (flags)
+        return -ENOTSUP;
+
+    cow_fd = open(filename, O_WRONLY | O_CREAT | O_TRUNC | O_BINARY,
+              0644);
+    if (cow_fd < 0)
+        return -1;
+    memset(&cow_header, 0, sizeof(cow_header));
+    cow_header.magic = cpu_to_be32(COW_MAGIC);
+    cow_header.version = cpu_to_be32(COW_VERSION);
+    if (image_filename) {
+        /* Note: if no file, we put a dummy mtime */
+        cow_header.mtime = cpu_to_be32(0);
+
+        fd = open(image_filename, O_RDONLY | O_BINARY);
+        if (fd < 0) {
+            close(cow_fd);
+            goto mtime_fail;
+        }
+        if (fstat(fd, &st) != 0) {
+            close(fd);
+            goto mtime_fail;
+        }
+        close(fd);
+        cow_header.mtime = cpu_to_be32(st.st_mtime);
+    mtime_fail:
+        pstrcpy(cow_header.backing_file, sizeof(cow_header.backing_file),
+                image_filename);
+    }
+    cow_header.sectorsize = cpu_to_be32(512);
+    cow_header.size = cpu_to_be64(image_sectors * 512);
+    write(cow_fd, &cow_header, sizeof(cow_header));
+    /* resize to include at least all the bitmap */
+    ftruncate(cow_fd, sizeof(cow_header) + ((image_sectors + 7) >> 3));
+    close(cow_fd);
+    return 0;
+}
+
+static void cow_flush(BlockDriverState *bs)
+{
+    BDRVCowState *s = bs->opaque;
+    fsync(s->fd);
+}
+
+BlockDriver bdrv_cow = {
+    "cow",
+    sizeof(BDRVCowState),
+    cow_probe,
+    cow_open,
+    cow_read,
+    cow_write,
+    cow_close,
+    cow_create,
+    cow_flush,
+    cow_is_allocated,
+};
+#endif