From e2b8247a322cd92945785edf25f09e6b3e8285f9 Mon Sep 17 00:00:00 2001 From: Jeff Cody Date: Fri, 7 Apr 2017 16:55:26 -0400 Subject: block: do not set BDS read_only if copy_on_read enabled 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 Reviewed-by: Stefan Hajnoczi Reviewed-by: John Snow Message-id: 0c5b4c1cc2c651471b131f21376dfd5ea24d2196.1491597120.git.jcody@redhat.com --- block/vvfat.c | 19 +++++++++++++++---- 1 file changed, 15 insertions(+), 4 deletions(-) (limited to 'block/vvfat.c') diff --git a/block/vvfat.c b/block/vvfat.c index d4ce6d7092..b509d55642 100644 --- a/block/vvfat.c +++ b/block/vvfat.c @@ -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 (!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; -- cgit v1.2.3