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From: Jeff Cody <jcody@redhat.com>
To: qemu-block@nongnu.org
Date: Fri, 21 Apr 2017 09:46:37 -0400
Message-Id: <20170421134644.10239-6-jcody@redhat.com>
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Subject: [Qemu-devel] [PULL 05/12] block: do not set BDS read_only if
copy_on_read enabled
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Cc: peter.maydell@linaro.org, jcody@redhat.com, qemu-devel@nongnu.org
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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=3Dvvfat,dir=3D/tmp/vvfat,rw,if=3Dvirtio,readonly=3Don"
This is not correct. Now, attempting to use the above -drive parameter
will result in an error (i.e., 'rw' is incompatible with 'readonly=3Don').
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@r=
edhat.com
---
block.c | 10 +++++++++-
block/bochs.c | 5 ++++-
block/cloop.c | 5 ++++-
block/dmg.c | 6 +++++-
block/rbd.c | 11 ++++++++++-
block/vvfat.c | 19 +++++++++++++++----
include/block/block.h | 2 +-
7 files changed, 48 insertions(+), 10 deletions(-)
diff --git a/block.c b/block.c
index 25a4cfd..4766b8a 100644
--- a/block.c
+++ b/block.c
@@ -192,9 +192,17 @@ void path_combine(char *dest, int dest_size,
}
}
=20
-void bdrv_set_read_only(BlockDriverState *bs, bool read_only)
+int bdrv_set_read_only(BlockDriverState *bs, bool read_only, Error **errp)
{
+ /* Do not set read_only if copy_on_read is enabled */
+ if (bs->copy_on_read && read_only) {
+ error_setg(errp, "Can't set node '%s' to r/o with copy-on-read ena=
bled",
+ bdrv_get_device_or_node_name(bs));
+ return -EINVAL;
+ }
+
bs->read_only =3D read_only;
+ return 0;
}
=20
void bdrv_get_full_backing_filename_from_filename(const char *backed,
diff --git a/block/bochs.c b/block/bochs.c
index bdc2831..a759b6e 100644
--- a/block/bochs.c
+++ b/block/bochs.c
@@ -110,7 +110,10 @@ static int bochs_open(BlockDriverState *bs, QDict *opt=
ions, int flags,
return -EINVAL;
}
=20
- bdrv_set_read_only(bs, true); /* no write support yet */
+ ret =3D bdrv_set_read_only(bs, true, errp); /* no write support yet */
+ if (ret < 0) {
+ return ret;
+ }
=20
ret =3D bdrv_pread(bs->file, 0, &bochs, sizeof(bochs));
if (ret < 0) {
diff --git a/block/cloop.c b/block/cloop.c
index 11f17c8..d6597fc 100644
--- a/block/cloop.c
+++ b/block/cloop.c
@@ -72,7 +72,10 @@ static int cloop_open(BlockDriverState *bs, QDict *optio=
ns, int flags,
return -EINVAL;
}
=20
- bdrv_set_read_only(bs, true);
+ ret =3D bdrv_set_read_only(bs, true, errp);
+ if (ret < 0) {
+ return ret;
+ }
=20
/* read header */
ret =3D bdrv_pread(bs->file, 128, &s->block_size, 4);
diff --git a/block/dmg.c b/block/dmg.c
index 27ce4a6..900ae5a 100644
--- a/block/dmg.c
+++ b/block/dmg.c
@@ -419,8 +419,12 @@ static int dmg_open(BlockDriverState *bs, QDict *optio=
ns, int flags,
return -EINVAL;
}
=20
+ ret =3D bdrv_set_read_only(bs, true, errp);
+ if (ret < 0) {
+ return ret;
+ }
+
block_module_load_one("dmg-bz2");
- bdrv_set_read_only(bs, true);
=20
s->n_chunks =3D 0;
s->offsets =3D s->lengths =3D s->sectors =3D s->sectorcounts =3D NULL;
diff --git a/block/rbd.c b/block/rbd.c
index 6ad2904..1c43171 100644
--- a/block/rbd.c
+++ b/block/rbd.c
@@ -635,13 +635,22 @@ static int qemu_rbd_open(BlockDriverState *bs, QDict =
*options, int flags,
goto failed_shutdown;
}
=20
+ /* rbd_open is always r/w */
r =3D rbd_open(s->io_ctx, s->name, &s->image, s->snap);
if (r < 0) {
error_setg_errno(errp, -r, "error reading header from %s", s->name=
);
goto failed_open;
}
=20
- bdrv_set_read_only(bs, (s->snap !=3D NULL));
+ /* If we are using an rbd snapshot, we must be r/o, otherwise
+ * leave as-is */
+ if (s->snap !=3D NULL) {
+ r =3D bdrv_set_read_only(bs, true, &local_err);
+ if (r < 0) {
+ error_propagate(errp, local_err);
+ goto failed_open;
+ }
+ }
=20
qemu_opts_del(opts);
return 0;
diff --git a/block/vvfat.c b/block/vvfat.c
index d4ce6d7..b509d55 100644
--- a/block/vvfat.c
+++ b/block/vvfat.c
@@ -1156,8 +1156,6 @@ static int vvfat_open(BlockDriverState *bs, QDict *op=
tions, int flags,
=20
s->current_cluster=3D0xffffffff;
=20
- /* read only is the default for safety */
- bdrv_set_read_only(bs, true);
s->qcow =3D NULL;
s->qcow_filename =3D NULL;
s->fat2 =3D NULL;
@@ -1169,11 +1167,24 @@ static int vvfat_open(BlockDriverState *bs, QDict *=
options, int flags,
s->sector_count =3D cyls * heads * secs - (s->first_sectors_number - 1=
);
=20
if (qemu_opt_get_bool(opts, "rw", false)) {
- ret =3D enable_write_target(bs, errp);
+ if (!bdrv_is_read_only(bs)) {
+ ret =3D enable_write_target(bs, errp);
+ if (ret < 0) {
+ goto fail;
+ }
+ } else {
+ ret =3D -EPERM;
+ error_setg(errp,
+ "Unable to set VVFAT to 'rw' when drive is read-onl=
y");
+ goto fail;
+ }
+ } else {
+ /* read only is the default for safety */
+ ret =3D bdrv_set_read_only(bs, true, &local_err);
if (ret < 0) {
+ error_propagate(errp, local_err);
goto fail;
}
- bdrv_set_read_only(bs, false);
}
=20
bs->total_sectors =3D cyls * heads * secs;
diff --git a/include/block/block.h b/include/block/block.h
index 16eb909..3525590 100644
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -434,7 +434,7 @@ int bdrv_is_allocated_above(BlockDriverState *top, Bloc=
kDriverState *base,
int64_t sector_num, int nb_sectors, int *pnum);
=20
bool bdrv_is_read_only(BlockDriverState *bs);
-void bdrv_set_read_only(BlockDriverState *bs, bool read_only);
+int bdrv_set_read_only(BlockDriverState *bs, bool read_only, Error **errp);
bool bdrv_is_sg(BlockDriverState *bs);
bool bdrv_is_inserted(BlockDriverState *bs);
int bdrv_media_changed(BlockDriverState *bs);
--=20
2.9.3