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block: do not set BDS read_only if copy_on_read enabled

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A few block drivers will set the BDS read_only flag from their
.bdrv_open() function.  This means the bs->read_only flag could
be set after we enable copy_on_read, as the BDRV_O_COPY_ON_READ
flag check occurs prior to the call to bdrv->bdrv_open().

This adds an error return to bdrv_set_read_only(), and an error will be
return if we try to set the BDS to read_only while copy_on_read is
enabled.

This patch also changes the behavior of vvfat.  Before, vvfat could
override the drive 'readonly' flag with its own, internal 'rw' flag.

For instance, this -drive parameter would result in a writable image:

"-drive format=vvfat,dir=/tmp/vvfat,rw,if=virtio,readonly=on"

This is not correct.  Now, attempting to use the above -drive parameter
will result in an error (i.e., 'rw' is incompatible with 'readonly=on').

Signed-off-by: Jeff Cody <jcody@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: John Snow <jsnow@redhat.com>
Message-id: 0c5b4c1cc2c651471b131f21376dfd5ea24d2196.1491597120.git.jcody@redhat.com
This commit is contained in:
Jeff Cody 2017-04-07 16:55:26 -04:00
parent fe5241bfe3
commit e2b8247a32
7 changed files with 49 additions and 11 deletions
Download patch file Download diff file Expand all files Collapse all files

21
block/vvfat.c
View file

@ -1156,8 +1156,6 @@ static int vvfat_open(BlockDriverState *bs, QDict *options, int flags,
s->current_cluster=0xffffffff;
/* read only is the default for safety */
bdrv_set_read_only(bs, true);
s->qcow = NULL;
s->qcow_filename = NULL;
s->fat2 = NULL;
@ -1169,11 +1167,24 @@ static int vvfat_open(BlockDriverState *bs, QDict *options, int flags,
s->sector_count = cyls * heads * secs - (s->first_sectors_number - 1);
if (qemu_opt_get_bool(opts, "rw", false)) {
ret = enable_write_target(bs, errp);
if (ret < 0) {
if (!bdrv_is_read_only(bs)) {
ret = enable_write_target(bs, errp);
if (ret < 0) {
goto fail;
}
} else {
ret = -EPERM;
error_setg(errp,
"Unable to set VVFAT to 'rw' when drive is read-only");
goto fail;
}
} else {
/* read only is the default for safety */
ret = bdrv_set_read_only(bs, true, &local_err);
if (ret < 0) {
error_propagate(errp, local_err);
goto fail;
}
bdrv_set_read_only(bs, false);
}
bs->total_sectors = cyls * heads * secs;