added user mode Linux Copy On Write disk image support - added -snapshot support (initial patch by Rusty Russell)

git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@309 c046a42c-6fe2-441c-8c8c-71466251a162

Makefile

@@ -28,7 +28,7 @@ else
 LDFLAGS+=-Wl,-shared
 endif
 ifeq ($(TARGET_ARCH), i386)
-PROGS+=vl
+PROGS+=vl vlmkcow
 endif
 endif
 
@@ -141,7 +141,10 @@ endif
 
 # must use static linking to avoid leaving stuff in virtual address space
 vl: vl.o block.o libqemu.a
-	$(CC) -static -Wl,-T,i386-vl.ld -o $@ $^  $(LIBS)
+	$(CC) -pg -static -Wl,-T,i386-vl.ld -o $@ $^  $(LIBS)
+
+vlmkcow: vlmkcow.o
+	$(CC) -o $@ $^  $(LIBS)
 
 depend: $(SRCS)
 	$(CC) -MM $(CFLAGS) $^ 1>.depend

block.c

@@ -38,58 +38,250 @@
 #include <sys/poll.h>
 #include <errno.h>
 #include <sys/wait.h>
+#include <netinet/in.h>
 
 #include "vl.h"
 
+#define NO_THUNK_TYPE_SIZE
+#include "thunk.h"
+
 struct BlockDriverState {
-    int fd;
+    int fd; /* if -1, only COW mappings */
     int64_t total_sectors;
     int read_only;
+
+    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;
+    int cow_fd;
+    int64_t cow_sectors_offset;
+    char filename[1024];
 };
 
-BlockDriverState *bdrv_open(const char *filename)
+BlockDriverState *bdrv_open(const char *filename, int snapshot)
 {
     BlockDriverState *bs;
-    int fd;
+    int fd, cow_fd;
     int64_t size;
+    char template[] = "/tmp/vl.XXXXXX";
+    struct cow_header_v2 cow_header;
+    struct stat st;
 
     bs = malloc(sizeof(BlockDriverState));
     if(!bs)
         return NULL;
     bs->read_only = 0;
-    fd = open(filename, O_RDWR);
+    bs->fd = -1;
+    bs->cow_fd = -1;
+    bs->cow_bitmap = NULL;
+    strcpy(bs->filename, filename);
+
+    /* open standard HD image */
+    fd = open(filename, O_RDWR | O_LARGEFILE);
     if (fd < 0) {
-        fd = open(filename, O_RDONLY);
+        /* read only image on disk */
+        fd = open(filename, O_RDONLY | O_LARGEFILE);
         if (fd < 0) {
-            close(fd);
+            perror(filename);
-            free(bs);
+            goto fail;
-            return NULL;
         }
+        if (!snapshot)
             bs->read_only = 1;
     }
+    bs->fd = fd;
+
+    /* see if it is a cow image */
+    if (read(fd, &cow_header, sizeof(cow_header)) != sizeof(cow_header)) {
+        fprintf(stderr, "%s: could not read header\n", filename);
+        goto fail;
+    }
+    if (cow_header.magic == htonl(COW_MAGIC) &&
+        cow_header.version == htonl(COW_VERSION)) {
+        /* cow image found */
+        size = cow_header.size;
+#ifndef WORDS_BIGENDIAN
+        size = bswap64(size);
+#endif    
+        bs->total_sectors = size / 512;
+
+        bs->cow_fd = fd;
+        bs->fd = -1;
+        if (cow_header.backing_file[0] != '\0') {
+            if (stat(cow_header.backing_file, &st) != 0) {
+                fprintf(stderr, "%s: could not find original disk image '%s'\n", filename, cow_header.backing_file);
+                goto fail;
+            }
+            if (st.st_mtime != htonl(cow_header.mtime)) {
+                fprintf(stderr, "%s: original raw disk image '%s' does not match saved timestamp\n", filename, cow_header.backing_file);
+                goto fail;
+            }
+            fd = open(cow_header.backing_file, O_RDONLY | O_LARGEFILE);
+            if (fd < 0)
+                goto fail;
+            bs->fd = fd;
+        }
+        /* mmap the bitmap */
+        bs->cow_bitmap_size = ((bs->total_sectors + 7) >> 3) + sizeof(cow_header);
+        bs->cow_bitmap_addr = mmap(get_mmap_addr(bs->cow_bitmap_size), 
+                                   bs->cow_bitmap_size, 
+                                   PROT_READ | PROT_WRITE,
+                                   MAP_SHARED, bs->cow_fd, 0);
+        if (bs->cow_bitmap_addr == MAP_FAILED)
+            goto fail;
+        bs->cow_bitmap = bs->cow_bitmap_addr + sizeof(cow_header);
+        bs->cow_sectors_offset = (bs->cow_bitmap_size + 511) & ~511;
+        snapshot = 0;
+    } else {
+        /* standard raw image */
         size = lseek64(fd, 0, SEEK_END);
         bs->total_sectors = size / 512;
         bs->fd = fd;
+    }
+
+    if (snapshot) {
+        /* create a temporary COW file */
+        cow_fd = mkstemp(template);
+        if (cow_fd < 0)
+            goto fail;
+        bs->cow_fd = cow_fd;
+	unlink(template);
+        
+        /* just need to allocate bitmap */
+        bs->cow_bitmap_size = (bs->total_sectors + 7) >> 3;
+        bs->cow_bitmap_addr = mmap(get_mmap_addr(bs->cow_bitmap_size), 
+                                   bs->cow_bitmap_size, 
+                                   PROT_READ | PROT_WRITE,
+                                   MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+        if (bs->cow_bitmap_addr == MAP_FAILED)
+            goto fail;
+        bs->cow_bitmap = bs->cow_bitmap_addr;
+        bs->cow_sectors_offset = 0;
+    }
+    
     return bs;
+ fail:
+    bdrv_close(bs);
+    return NULL;
 }
 
 void bdrv_close(BlockDriverState *bs)
 {
+    /* we unmap the mapping so that it is written to the COW file */
+    if (bs->cow_bitmap_addr)
+        munmap(bs->cow_bitmap_addr, bs->cow_bitmap_size);
+    if (bs->cow_fd >= 0)
+        close(bs->cow_fd);
+    if (bs->fd >= 0)
         close(bs->fd);
     free(bs);
 }
 
+static inline void 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 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;
+}
+
+/* commit COW file into the raw image */
+int bdrv_commit(BlockDriverState *bs)
+{
+    int64_t i;
+    uint8_t *cow_bitmap;
+
+    if (!bs->cow_bitmap) {
+	fprintf(stderr, "Already committed to %s\n", bs->filename);
+	return 0;
+    }
+
+    if (bs->read_only) {
+	fprintf(stderr, "Can't commit to %s: read-only\n", bs->filename);
+	return -1;
+    }
+
+    cow_bitmap = bs->cow_bitmap;
+    for (i = 0; i < bs->total_sectors; i++) {
+	if (is_bit_set(cow_bitmap, i)) {
+	    unsigned char sector[512];
+	    if (bdrv_read(bs, i, sector, 1) != 0) {
+		fprintf(stderr, "Error reading sector %lli: aborting commit\n",
+			(long long)i);
+		return -1;
+	    }
+
+	    /* Make bdrv_write write to real file for a moment. */
+	    bs->cow_bitmap = NULL;
+	    if (bdrv_write(bs, i, sector, 1) != 0) {
+		fprintf(stderr, "Error writing sector %lli: aborting commit\n",
+			(long long)i);
+		bs->cow_bitmap = cow_bitmap;
+		return -1;
+	    }
+	    bs->cow_bitmap = cow_bitmap;
+	}
+    }
+    fprintf(stderr, "Committed snapshot to %s\n", bs->filename);
+    return 0;
+}
+
 /* return -1 if error */
 int bdrv_read(BlockDriverState *bs, int64_t sector_num, 
               uint8_t *buf, int nb_sectors)
 {
-    int ret;
+    int ret, n, fd;
+    int64_t offset;
     
-    lseek64(bs->fd, sector_num * 512, SEEK_SET);
+    while (nb_sectors > 0) {
-    ret = read(bs->fd, buf, nb_sectors * 512);
+        if (is_changed(bs->cow_bitmap, sector_num, nb_sectors, &n)) {
-    if (ret != nb_sectors * 512)
+            fd = bs->cow_fd;
+            offset = bs->cow_sectors_offset;
+        } else {
+            fd = bs->fd;
+            offset = 0;
+        }
+
+        if (fd < 0) {
+            /* no file, just return empty sectors */
+            memset(buf, 0, n * 512);
+        } else {
+            offset += sector_num * 512;
+            lseek64(fd, offset, SEEK_SET);
+            ret = read(fd, buf, n * 512);
+            if (ret != n * 512) {
                 return -1;
-    else
+            }
+        }
+        nb_sectors -= n;
+        sector_num += n;
+        buf += n * 512;
+    }
     return 0;
 }
 
@@ -97,16 +289,34 @@ int bdrv_read(BlockDriverState *bs, int64_t sector_num,
 int bdrv_write(BlockDriverState *bs, int64_t sector_num, 
                const uint8_t *buf, int nb_sectors)
 {
-    int ret;
+    int ret, fd, i;
+    int64_t offset, retl;
 
     if (bs->read_only)
         return -1;
 
-    lseek64(bs->fd, sector_num * 512, SEEK_SET);
+    if (bs->cow_bitmap) {
-    ret = write(bs->fd, buf, nb_sectors * 512);
+        fd = bs->cow_fd;
-    if (ret != nb_sectors * 512)
+        offset = bs->cow_sectors_offset;
+    } else {
+        fd = bs->fd;
+        offset = 0;
+    }
+    
+    offset += sector_num * 512;
+    retl = lseek64(fd, offset, SEEK_SET);
+    if (retl == -1) {
         return -1;
-    else
+    }
+    ret = write(fd, buf, nb_sectors * 512);
+    if (ret != nb_sectors * 512) {
+        return -1;
+    }
+
+    if (bs->cow_bitmap) {
+	for (i = 0; i < nb_sectors; i++)
+	    set_bit(bs->cow_bitmap, sector_num + i);
+    }
     return 0;
 }
 

vl.c

@@ -63,6 +63,8 @@
 #define INITRD_LOAD_ADDR   0x00400000
 #define KERNEL_PARAMS_ADDR 0x00090000
 
+#define MAX_DISKS 2
+
 /* from plex86 (BSD license) */
 struct  __attribute__ ((packed)) linux_params {
   // For 0x00..0x3f, see 'struct screen_info' in linux/include/linux/tty.h.
@@ -190,6 +192,7 @@ FILE *logfile = NULL;
 int loglevel;
 IOPortReadFunc *ioport_read_table[3][MAX_IOPORTS];
 IOPortWriteFunc *ioport_write_table[3][MAX_IOPORTS];
+BlockDriverState *bs_table[MAX_DISKS];
 
 /***********************************************************/
 /* x86 io ports */
@@ -1265,6 +1268,7 @@ void term_print_help(void)
     printf("\n"
            "C-a h    print this help\n"
            "C-a x    exit emulatior\n"
+	   "C-a s    save disk data back to file (if -snapshot)\n"
            "C-a b    send break (magic sysrq)\n"
            "C-a C-a  send C-a\n"
            );
@@ -1282,6 +1286,15 @@ void serial_received_byte(SerialState *s, int ch)
         case 'x':
             exit(0);
             break;
+	case 's': 
+            {
+                int i;
+                for (i = 0; i < MAX_DISKS; i++) {
+                    if (bs_table[i])
+                        bdrv_commit(bs_table[i]);
+                }
+	    }
+            break;
         case 'b':
             /* send break */
             s->rbr = 0;
@@ -1976,8 +1989,6 @@ void ne2000_init(void)
 /* set to 1 set disable mult support */
 #define MAX_MULT_SECTORS 8
 
-#define MAX_DISKS 2
-
 struct IDEState;
 
 typedef void EndTransferFunc(struct IDEState *);
@@ -2009,7 +2020,6 @@ typedef struct IDEState {
     uint8_t io_buffer[MAX_MULT_SECTORS*512 + 4];
 } IDEState;
 
-BlockDriverState *bs_table[MAX_DISKS];
 IDEState ide_state[MAX_DISKS];
 
 static void padstr(char *str, const char *src, int len)
@@ -2513,6 +2523,16 @@ static void host_alarm_handler(int host_signum, siginfo_t *info,
     }
 }
 
+unsigned long mmap_addr = PHYS_RAM_BASE;
+
+void *get_mmap_addr(unsigned long size)
+{
+    unsigned long addr;
+    addr = mmap_addr;
+    mmap_addr += ((size + 4095) & ~4095) + 4096;
+    return (void *)addr;
+}
+
 /* main execution loop */
 
 CPUState *cpu_gdbstub_get_env(void *opaque)
@@ -2612,6 +2632,7 @@ void help(void)
            "-initrd file   use 'file' as initial ram disk\n"
            "-hda file      use 'file' as hard disk 0 image\n"
            "-hdb file      use 'file' as hard disk 1 image\n"
+	   "-snapshot      write to temporary files instead of disk image files\n"
            "-m megs        set virtual RAM size to megs MB\n"
            "-n script      set network init script [default=%s]\n"
            "\n"
@@ -2630,12 +2651,14 @@ struct option long_options[] = {
     { "initrd", 1, NULL, 0, },
     { "hda", 1, NULL, 0, },
     { "hdb", 1, NULL, 0, },
+    { "snapshot", 0, NULL, 0, },
     { NULL, 0, NULL, 0 },
 };
 
 int main(int argc, char **argv)
 {
     int c, ret, initrd_size, i, use_gdbstub, gdbstub_port, long_index;
+    int snapshot;
     struct linux_params *params;
     struct sigaction act;
     struct itimerval itv;
@@ -2652,6 +2675,7 @@ int main(int argc, char **argv)
     pstrcpy(network_script, sizeof(network_script), DEFAULT_NETWORK_SCRIPT);
     use_gdbstub = 0;
     gdbstub_port = DEFAULT_GDBSTUB_PORT;
+    snapshot = 0;
     for(;;) {
         c = getopt_long_only(argc, argv, "hm:dn:sp:", long_options, &long_index);
         if (c == -1)
@@ -2668,6 +2692,9 @@ int main(int argc, char **argv)
             case 2:
                 hd_filename[1] = optarg;
                 break;
+            case 3:
+                snapshot = 1;
+                break;
             }
             break;
         case 'h':
@@ -2711,18 +2738,6 @@ int main(int argc, char **argv)
         setvbuf(logfile, NULL, _IOLBF, 0);
     }
 
-    /* open the virtual block devices */
-    for(i = 0; i < MAX_DISKS; i++) {
-        if (hd_filename[i]) {
-            bs_table[i] = bdrv_open(hd_filename[i]);
-            if (!bs_table[i]) {
-                fprintf(stderr, "vl: could not open hard disk image '%s\n",
-                        hd_filename[i]);
-                exit(1);
-            }
-        }
-    }
-
     /* init network tun interface */
     net_init();
 
@@ -2744,7 +2759,7 @@ int main(int argc, char **argv)
     }
     ftruncate(phys_ram_fd, phys_ram_size);
     unlink(phys_ram_file);
-    phys_ram_base = mmap((void *)PHYS_RAM_BASE, phys_ram_size, 
+    phys_ram_base = mmap(get_mmap_addr(phys_ram_size), phys_ram_size, 
                          PROT_WRITE | PROT_READ, MAP_SHARED | MAP_FIXED, 
                          phys_ram_fd, 0);
     if (phys_ram_base == MAP_FAILED) {
@@ -2752,6 +2767,18 @@ int main(int argc, char **argv)
         exit(1);
     }
 
+    /* open the virtual block devices */
+    for(i = 0; i < MAX_DISKS; i++) {
+        if (hd_filename[i]) {
+            bs_table[i] = bdrv_open(hd_filename[i], snapshot);
+            if (!bs_table[i]) {
+                fprintf(stderr, "vl: could not open hard disk image '%s\n",
+                        hd_filename[i]);
+                exit(1);
+            }
+        }
+    }
+
     /* now we can load the kernel */
     ret = load_kernel(argv[optind], phys_ram_base + KERNEL_LOAD_ADDR);
     if (ret < 0) {

vl.h

@@ -24,16 +24,32 @@
 #ifndef VL_H
 #define VL_H
 
+/* vl.c */
+void *get_mmap_addr(unsigned long size);
+
 /* block.c */
 typedef struct BlockDriverState BlockDriverState;
 
-BlockDriverState *bdrv_open(const char *filename);
+BlockDriverState *bdrv_open(const char *filename, int snapshot);
 void bdrv_close(BlockDriverState *bs);
 int bdrv_read(BlockDriverState *bs, int64_t sector_num, 
               uint8_t *buf, int nb_sectors);
 int bdrv_write(BlockDriverState *bs, int64_t sector_num, 
                const uint8_t *buf, int nb_sectors);
 void bdrv_get_geometry(BlockDriverState *bs, int64_t *nb_sectors_ptr);
+int bdrv_commit(BlockDriverState *bs);
 
+/* user mode linux compatible COW file */
+#define COW_MAGIC 0x4f4f4f4d  /* MOOO */
+#define COW_VERSION 2
+
+struct cow_header_v2 {
+    uint32_t magic;
+    uint32_t  long version;
+    char backing_file[1024];
+    int32_t mtime;
+    uint64_t size;
+    uint32_t sectorsize;
+};
 
 #endif /* VL_H */

vlmkcow.c

@@ -0,0 +1,142 @@
+/*
+ * create a COW disk image
+ * 
+ * Copyright (c) 2003 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.
+ */
+#include <stdlib.h>
+#include <stdio.h>
+#include <stdarg.h>
+#include <string.h>
+#include <getopt.h>
+#include <inttypes.h>
+#include <unistd.h>
+#include <sys/mman.h>
+#include <fcntl.h>
+#include <signal.h>
+#include <time.h>
+#include <sys/time.h>
+#include <malloc.h>
+#include <termios.h>
+#include <sys/poll.h>
+#include <errno.h>
+#include <sys/wait.h>
+#include <netinet/in.h>
+
+#include "vl.h"
+
+#define NO_THUNK_TYPE_SIZE
+#include "thunk.h"
+
+int cow_create(int cow_fd, const char *image_filename, 
+               int64_t image_sectors)
+{
+    struct cow_header_v2 cow_header;
+    int fd;
+    struct stat st;
+
+    memset(&cow_header, 0, sizeof(cow_header));
+    cow_header.magic = htonl(COW_MAGIC);
+    cow_header.version = htonl(COW_VERSION);
+    if (image_filename) {
+        fd = open(image_filename, O_RDONLY);
+        if (fd < 0) {
+            perror(image_filename);
+            exit(1);
+        }
+        image_sectors = lseek64(fd, 0, SEEK_END);
+        if (fstat(fd, &st) != 0) {
+            close(fd);
+            return -1;
+        }
+        close(fd);
+        image_sectors /= 512;
+        cow_header.mtime = htonl(st.st_mtime);
+        realpath(image_filename, cow_header.backing_file);
+    }
+    cow_header.sectorsize = htonl(512);
+    cow_header.size = image_sectors * 512;
+#ifndef WORDS_BIGENDIAN
+    cow_header.size = bswap64(cow_header.size);
+#endif    
+    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));
+    lseek(cow_fd, 0, SEEK_SET);
+    return 0;
+}
+
+void help(void)
+{
+    printf("usage vlmkcow [-h] [-f disk_image] cow_image [cow_size]\n"
+           "Create a Copy On Write disk image from an optional raw disk image\n"
+           "\n"
+           "-f disk_image   set the raw disk image name\n"
+           "cow_image       the created cow_image\n"
+           "cow_size        the create cow_image size in MB if no raw disk image is used\n"
+           "\n"
+           "Once the cow_image is created from a raw disk image, you must not modify the original raw disk image\n"
+           );
+    exit(1);
+}
+
+int main(int argc, char **argv)
+{
+    const char *image_filename, *cow_filename;
+    int cow_fd, c, nb_args;
+    int64_t image_size;
+    
+    image_filename = NULL;
+    image_size = 0;
+    for(;;) {
+        c = getopt(argc, argv, "hf:");
+        if (c == -1)
+            break;
+        switch(c) {
+        case 'h':
+            help();
+            break;
+        case 'f':
+            image_filename = optarg;
+            break;
+        }
+    }
+    if (!image_filename)
+        nb_args = 2;
+    else
+        nb_args = 1;
+    if (optind + nb_args != argc)
+        help();
+
+    cow_filename = argv[optind];
+    if (nb_args == 2) {
+        image_size = (int64_t)atoi(argv[optind + 1]) * 2 * 1024;
+    }
+
+    cow_fd = open(cow_filename, O_RDWR | O_CREAT | O_TRUNC, 0644);
+    if (!cow_fd < 0)
+        return -1;
+    if (cow_create(cow_fd, image_filename, image_size) < 0) {
+        fprintf(stderr, "%s: error while formating\n", cow_filename);
+        exit(1);
+    }
+    close(cow_fd);
+    return 0;
+}