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authorFederico Simoncelli <fsimonce@redhat.com>2011-06-20 12:48:19 -0400
committerKevin Wolf <kwolf@redhat.com>2011-07-05 11:23:29 +0200
commit661a0f712b7c5b78408d85ba8b7f47ce44f395c0 (patch)
tree8c03df5b089035ff4dc1513db25ddd30ec27d344 /qemu-img.c
parent02854532c215872b2af5ed48af93b7a309de1b1b (diff)
qemu-img: Add cache command line option
qemu-img currently writes disk images using writeback and filling up the cache buffers which are then flushed by the kernel preventing other processes from accessing the storage. This is particularly bad in cluster environments where time-based algorithms might be in place and accessing the storage within certain timeouts is critical. This patch adds the option to choose a cache method when writing disk images. Signed-off-by: Federico Simoncelli <fsimonce@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Diffstat (limited to 'qemu-img.c')
-rw-r--r--qemu-img.c80
1 files changed, 67 insertions, 13 deletions
diff --git a/qemu-img.c b/qemu-img.c
index 32628b3110..54137a4e92 100644
--- a/qemu-img.c
+++ b/qemu-img.c
@@ -40,6 +40,7 @@ typedef struct img_cmd_t {
/* Default to cache=writeback as data integrity is not important for qemu-tcg. */
#define BDRV_O_FLAGS BDRV_O_CACHE_WB
+#define BDRV_DEFAULT_CACHE "writeback"
static void format_print(void *opaque, const char *name)
{
@@ -64,6 +65,8 @@ static void help(void)
"Command parameters:\n"
" 'filename' is a disk image filename\n"
" 'fmt' is the disk image format. It is guessed automatically in most cases\n"
+ " 'cache' is the cache mode used to write the output disk image, the valid\n"
+ " options are: 'none', 'writeback' (default), 'writethrough' and 'unsafe'\n"
" 'size' is the disk image size in bytes. Optional suffixes\n"
" 'k' or 'K' (kilobyte, 1024), 'M' (megabyte, 1024k), 'G' (gigabyte, 1024M)\n"
" and T (terabyte, 1024G) are supported. 'b' is ignored.\n"
@@ -180,6 +183,27 @@ static int read_password(char *buf, int buf_size)
}
#endif
+static int set_cache_flag(const char *mode, int *flags)
+{
+ *flags &= ~BDRV_O_CACHE_MASK;
+
+ if (!strcmp(mode, "none") || !strcmp(mode, "off")) {
+ *flags |= BDRV_O_CACHE_WB;
+ *flags |= BDRV_O_NOCACHE;
+ } else if (!strcmp(mode, "writeback")) {
+ *flags |= BDRV_O_CACHE_WB;
+ } else if (!strcmp(mode, "unsafe")) {
+ *flags |= BDRV_O_CACHE_WB;
+ *flags |= BDRV_O_NO_FLUSH;
+ } else if (!strcmp(mode, "writethrough")) {
+ /* this is the default */
+ } else {
+ return -1;
+ }
+
+ return 0;
+}
+
static int print_block_option_help(const char *filename, const char *fmt)
{
BlockDriver *drv, *proto_drv;
@@ -441,13 +465,14 @@ static int img_check(int argc, char **argv)
static int img_commit(int argc, char **argv)
{
- int c, ret;
- const char *filename, *fmt;
+ int c, ret, flags;
+ const char *filename, *fmt, *cache;
BlockDriverState *bs;
fmt = NULL;
+ cache = BDRV_DEFAULT_CACHE;
for(;;) {
- c = getopt(argc, argv, "f:h");
+ c = getopt(argc, argv, "f:ht:");
if (c == -1) {
break;
}
@@ -459,6 +484,9 @@ static int img_commit(int argc, char **argv)
case 'f':
fmt = optarg;
break;
+ case 't':
+ cache = optarg;
+ break;
}
}
if (optind >= argc) {
@@ -466,7 +494,14 @@ static int img_commit(int argc, char **argv)
}
filename = argv[optind++];
- bs = bdrv_new_open(filename, fmt, BDRV_O_FLAGS | BDRV_O_RDWR);
+ flags = BDRV_O_RDWR;
+ ret = set_cache_flag(cache, &flags);
+ if (ret < 0) {
+ error_report("Invalid cache option: %s", cache);
+ return -1;
+ }
+
+ bs = bdrv_new_open(filename, fmt, flags);
if (!bs) {
return 1;
}
@@ -591,8 +626,8 @@ static int compare_sectors(const uint8_t *buf1, const uint8_t *buf2, int n,
static int img_convert(int argc, char **argv)
{
int c, ret = 0, n, n1, bs_n, bs_i, compress, cluster_size, cluster_sectors;
- int progress = 0;
- const char *fmt, *out_fmt, *out_baseimg, *out_filename;
+ int progress = 0, flags;
+ const char *fmt, *out_fmt, *cache, *out_baseimg, *out_filename;
BlockDriver *drv, *proto_drv;
BlockDriverState **bs = NULL, *out_bs = NULL;
int64_t total_sectors, nb_sectors, sector_num, bs_offset;
@@ -608,10 +643,11 @@ static int img_convert(int argc, char **argv)
fmt = NULL;
out_fmt = "raw";
+ cache = "unsafe";
out_baseimg = NULL;
compress = 0;
for(;;) {
- c = getopt(argc, argv, "f:O:B:s:hce6o:p");
+ c = getopt(argc, argv, "f:O:B:s:hce6o:pt:");
if (c == -1) {
break;
}
@@ -649,6 +685,9 @@ static int img_convert(int argc, char **argv)
case 'p':
progress = 1;
break;
+ case 't':
+ cache = optarg;
+ break;
}
}
@@ -779,8 +818,14 @@ static int img_convert(int argc, char **argv)
goto out;
}
- out_bs = bdrv_new_open(out_filename, out_fmt,
- BDRV_O_FLAGS | BDRV_O_RDWR | BDRV_O_NO_FLUSH);
+ flags = BDRV_O_RDWR;
+ ret = set_cache_flag(cache, &flags);
+ if (ret < 0) {
+ error_report("Invalid cache option: %s", cache);
+ return -1;
+ }
+
+ out_bs = bdrv_new_open(out_filename, out_fmt, flags);
if (!out_bs) {
ret = -1;
goto out;
@@ -1225,18 +1270,18 @@ static int img_rebase(int argc, char **argv)
BlockDriverState *bs, *bs_old_backing = NULL, *bs_new_backing = NULL;
BlockDriver *old_backing_drv, *new_backing_drv;
char *filename;
- const char *fmt, *out_basefmt, *out_baseimg;
+ const char *fmt, *cache, *out_basefmt, *out_baseimg;
int c, flags, ret;
int unsafe = 0;
int progress = 0;
/* Parse commandline parameters */
fmt = NULL;
+ cache = BDRV_DEFAULT_CACHE;
out_baseimg = NULL;
out_basefmt = NULL;
-
for(;;) {
- c = getopt(argc, argv, "uhf:F:b:p");
+ c = getopt(argc, argv, "uhf:F:b:pt:");
if (c == -1) {
break;
}
@@ -1260,6 +1305,9 @@ static int img_rebase(int argc, char **argv)
case 'p':
progress = 1;
break;
+ case 't':
+ cache = optarg;
+ break;
}
}
@@ -1271,13 +1319,19 @@ static int img_rebase(int argc, char **argv)
qemu_progress_init(progress, 2.0);
qemu_progress_print(0, 100);
+ flags = BDRV_O_RDWR | (unsafe ? BDRV_O_NO_BACKING : 0);
+ ret = set_cache_flag(cache, &flags);
+ if (ret < 0) {
+ error_report("Invalid cache option: %s", cache);
+ return -1;
+ }
+
/*
* Open the images.
*
* Ignore the old backing file for unsafe rebase in case we want to correct
* the reference to a renamed or moved backing file.
*/
- flags = BDRV_O_FLAGS | BDRV_O_RDWR | (unsafe ? BDRV_O_NO_BACKING : 0);
bs = bdrv_new_open(filename, fmt, flags);
if (!bs) {
return 1;