block: add -drive copy-on-read=on|off
This patch adds the -drive copy-on-read=on|off command-line option:
copy-on-read=on|off
copy-on-read is "on" or "off" and enables whether to copy read backing
file sectors into the image file. Copy-on-read avoids accessing the
same backing file sectors repeatedly and is useful when the backing
file is over a slow network. By default copy-on-read is off.
Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
diff --git a/blockdev.c b/blockdev.c
index 9068c5b..af4e239 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -257,6 +257,7 @@
DriveInfo *dinfo;
BlockIOLimit io_limits;
int snapshot = 0;
+ bool copy_on_read;
int ret;
translation = BIOS_ATA_TRANSLATION_AUTO;
@@ -273,6 +274,7 @@
snapshot = qemu_opt_get_bool(opts, "snapshot", 0);
ro = qemu_opt_get_bool(opts, "readonly", 0);
+ copy_on_read = qemu_opt_get_bool(opts, "copy-on-read", false);
file = qemu_opt_get(opts, "file");
serial = qemu_opt_get(opts, "serial");
@@ -546,6 +548,10 @@
bdrv_flags |= (BDRV_O_SNAPSHOT|BDRV_O_CACHE_WB|BDRV_O_NO_FLUSH);
}
+ if (copy_on_read) {
+ bdrv_flags |= BDRV_O_COPY_ON_READ;
+ }
+
if (media == MEDIA_CDROM) {
/* CDROM is fine for any interface, don't check. */
ro = 1;