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block/ssh: Set bdrv_has_zero_init according to the file type. 

If the remote is a regular file, set it to true (ie. reads of
uninitialized areas in a newly created file will return zeroes).
If we can't prove that, return false (a safe default).

Tested by adding a debugging print statement [not part of this commit]
and creating a remote file and a remote block device:

  $ ./qemu-img create ssh://localhost/tmp/new 100M
  Formatting 'ssh://localhost/tmp/new', fmt=raw size=104857600
  filename ssh://localhost/tmp/new: has_zero_init = 1
  $ sudo lvcreate -L 1G -n tmp /dev/fedora
    Logical volume "tmp" created
  $ ./qemu-img create ssh://localhost/dev/fedora/tmp 1G
  Formatting 'ssh://localhost/dev/fedora/tmp', fmt=raw size=1073741824
  filename ssh://localhost/dev/fedora/tmp: has_zero_init = 0

Cc: Kevin Wolf <kwolf@redhat.com>
Cc: qemu-stable@nongnu.org
Signed-off-by: Richard W.M. Jones <rjones@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Richard W.M. Jones 2013-06-25 18:15:18 +01:00 committed by Kevin Wolf
parent f59fee8d50
commit 0b3f21e6a9
1 changed files with 16 additions and 0 deletions
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16
block/ssh.c
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@ -716,6 +716,21 @@ static void ssh_close(BlockDriverState *bs)
ssh_state_free(s);
}
static int ssh_has_zero_init(BlockDriverState *bs)
{
BDRVSSHState *s = bs->opaque;
/* Assume false, unless we can positively prove it's true. */
int has_zero_init = 0;
if (s->attrs.flags & LIBSSH2_SFTP_ATTR_PERMISSIONS) {
if (s->attrs.permissions & LIBSSH2_SFTP_S_IFREG) {
has_zero_init = 1;
}
}
return has_zero_init;
}
static void restart_coroutine(void *opaque)
{
Coroutine *co = opaque;
@ -1037,6 +1052,7 @@ static BlockDriver bdrv_ssh = {
.bdrv_file_open = ssh_file_open,
.bdrv_create = ssh_create,
.bdrv_close = ssh_close,
.bdrv_has_zero_init = ssh_has_zero_init,
.bdrv_co_readv = ssh_co_readv,
.bdrv_co_writev = ssh_co_writev,
.bdrv_getlength = ssh_getlength,