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block: add -drive copy-on-read=on|off

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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>
This commit is contained in:
Stefan Hajnoczi 2011-11-17 13:40:32 +00:00 • committed by Kevin Wolf
parent ab1859218a
commit fb0490f69f
4 changed files with 21 additions and 3 deletions
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6
blockdev.c
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@ -257,6 +257,7 @@ DriveInfo *drive_init(QemuOpts *opts, int default_to_scsi)
DriveInfo *dinfo;
BlockIOLimit io_limits;
int snapshot = 0;
bool copy_on_read;
int ret;
translation = BIOS_ATA_TRANSLATION_AUTO;
@ -273,6 +274,7 @@ DriveInfo *drive_init(QemuOpts *opts, int default_to_scsi)
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 @@ DriveInfo *drive_init(QemuOpts *opts, int default_to_scsi)
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;