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block: Formats don't need CONSISTENT_READ with NO_IO

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Commit 1f4ad7d fixed 'qemu-img info' for raw images that are currently
in use as a mirror target. It is not enough for image formats, though,
as these still unconditionally request BLK_PERM_CONSISTENT_READ.

As this permission is geared towards whether the guest-visible data is
consistent, and has no impact on whether the metadata is sane, and
'qemu-img info' does not read guest-visible data (except for the raw
format), it makes sense to not require BLK_PERM_CONSISTENT_READ if there
is not going to be any guest I/O performed, regardless of image format.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Kevin Wolf 2017-11-30 17:38:43 +01:00
parent 281f327487
commit 5fbfabd313
1 changed files with 5 additions and 1 deletions
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6
block.c
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@ -1924,6 +1924,8 @@ void bdrv_format_default_perms(BlockDriverState *bs, BdrvChild *c,
assert(role == &child_backing || role == &child_file);
if (!backing) {
int flags = bdrv_reopen_get_flags(reopen_queue, bs);
/* Apart from the modifications below, the same permissions are
* forwarded and left alone as for filters */
bdrv_filter_default_perms(bs, c, role, reopen_queue, perm, shared,
@ -1936,7 +1938,9 @@ void bdrv_format_default_perms(BlockDriverState *bs, BdrvChild *c,
/* bs->file always needs to be consistent because of the metadata. We
* can never allow other users to resize or write to it. */
perm |= BLK_PERM_CONSISTENT_READ;
if (!(flags & BDRV_O_NO_IO)) {
perm |= BLK_PERM_CONSISTENT_READ;
}
shared &= ~(BLK_PERM_WRITE | BLK_PERM_RESIZE);
} else {
/* We want consistent read from backing files if the parent needs it.