Some block drivers have traditionally changed their node to read-only
mode without asking the user. This behaviour has been marked deprecated
since 2.11, expecting users to provide an explicit read-only=on option.
Now that we have auto-read-only=on, enable these drivers to make use of
the option.
This is the only use of bdrv_set_read_only(), so we can make it a bit
more specific and turn it into a bdrv_apply_auto_read_only() that is
more convenient for drivers to use.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
include/block/block.h | 3 ++-
block.c | 37 +++++++++++++++++++++++--------------
block/bochs.c | 17 ++++++-----------
block/cloop.c | 16 +++++-----------
block/dmg.c | 16 +++++-----------
block/rbd.c | 14 ++++----------
block/vvfat.c | 12 +++---------
7 files changed, 48 insertions(+), 67 deletions(-)
diff --git a/include/block/block.h b/include/block/block.h
index 580b3716c3..7f5453b45b 100644
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -438,7 +438,8 @@ int bdrv_is_allocated_above(BlockDriverState *top, BlockDriverState *base,
bool bdrv_is_read_only(BlockDriverState *bs);
int bdrv_can_set_read_only(BlockDriverState *bs, bool read_only,
bool ignore_allow_rdw, Error **errp);
-int bdrv_set_read_only(BlockDriverState *bs, bool read_only, Error **errp);
+int bdrv_apply_auto_read_only(BlockDriverState *bs, const char *errmsg,
+ Error **errp);
bool bdrv_is_writable(BlockDriverState *bs);
bool bdrv_is_sg(BlockDriverState *bs);
bool bdrv_is_inserted(BlockDriverState *bs);
diff --git a/block.c b/block.c
index f999393e28..631501bcae 100644
--- a/block.c
+++ b/block.c
@@ -266,27 +266,36 @@ int bdrv_can_set_read_only(BlockDriverState *bs, bool read_only,
return 0;
}
-/* TODO Remove (deprecated since 2.11)
- * Block drivers are not supposed to automatically change bs->read_only.
- * Instead, they should just check whether they can provide what the user
- * explicitly requested and error out if read-write is requested, but they can
- * only provide read-only access. */
-int bdrv_set_read_only(BlockDriverState *bs, bool read_only, Error **errp)
+/*
+ * Called by a driver that can only provide a read-only image.
+ *
+ * Returns 0 if the node is already read-only or it could switch the node to
+ * read-only because BDRV_O_AUTO_RDONLY is set.
+ *
+ * Returns -EACCES if the node is read-write and BDRV_O_AUTO_RDONLY is not set.
+ * If @errmsg is not NULL, it is used as the error message for the Error
+ * object.
+ */
+int bdrv_apply_auto_read_only(BlockDriverState *bs, const char *errmsg,
+ Error **errp)
{
int ret = 0;
- ret = bdrv_can_set_read_only(bs, read_only, false, errp);
+ if (!(bs->open_flags & BDRV_O_RDWR)) {
+ return 0;
+ }
+ if (!(bs->open_flags & BDRV_O_AUTO_RDONLY)) {
+ error_setg(errp, "%s", errmsg ?: "Image is read-only");
+ return -EACCES;
+ }
+
+ ret = bdrv_can_set_read_only(bs, true, false, errp);
if (ret < 0) {
return ret;
}
- bs->read_only = read_only;
-
- if (read_only) {
- bs->open_flags &= ~BDRV_O_RDWR;
- } else {
- bs->open_flags |= BDRV_O_RDWR;
- }
+ bs->read_only = true;
+ bs->open_flags &= ~BDRV_O_RDWR;
return 0;
}
diff --git a/block/bochs.c b/block/bochs.c
index 50c630047b..22e7d44211 100644
--- a/block/bochs.c
+++ b/block/bochs.c
@@ -105,23 +105,18 @@ static int bochs_open(BlockDriverState *bs, QDict *options, int flags,
struct bochs_header bochs;
int ret;
+ /* No write support yet */
+ ret = bdrv_apply_auto_read_only(bs, NULL, errp);
+ if (ret < 0) {
+ return ret;
+ }
+
bs->file = bdrv_open_child(NULL, options, "file", bs, &child_file,
false, errp);
if (!bs->file) {
return -EINVAL;
}
- if (!bdrv_is_read_only(bs)) {
- error_report("Opening bochs images without an explicit read-only=on "
- "option is deprecated. Future versions will refuse to "
- "open the image instead of automatically marking the "
- "image read-only.");
- ret = bdrv_set_read_only(bs, true, errp); /* no write support yet */
- if (ret < 0) {
- return ret;
- }
- }
-
ret = bdrv_pread(bs->file, 0, &bochs, sizeof(bochs));
if (ret < 0) {
return ret;
diff --git a/block/cloop.c b/block/cloop.c
index 2be68987bd..df2b85f723 100644
--- a/block/cloop.c
+++ b/block/cloop.c
@@ -67,23 +67,17 @@ static int cloop_open(BlockDriverState *bs, QDict *options, int flags,
uint32_t offsets_size, max_compressed_block_size = 1, i;
int ret;
+ ret = bdrv_apply_auto_read_only(bs, NULL, errp);
+ if (ret < 0) {
+ return ret;
+ }
+
bs->file = bdrv_open_child(NULL, options, "file", bs, &child_file,
false, errp);
if (!bs->file) {
return -EINVAL;
}
- if (!bdrv_is_read_only(bs)) {
- error_report("Opening cloop images without an explicit read-only=on "
- "option is deprecated. Future versions will refuse to "
- "open the image instead of automatically marking the "
- "image read-only.");
- ret = bdrv_set_read_only(bs, true, errp);
- if (ret < 0) {
- return ret;
- }
- }
-
/* read header */
ret = bdrv_pread(bs->file, 128, &s->block_size, 4);
if (ret < 0) {
diff --git a/block/dmg.c b/block/dmg.c
index c9b3c519c4..1d9283ba2f 100644
--- a/block/dmg.c
+++ b/block/dmg.c
@@ -413,23 +413,17 @@ static int dmg_open(BlockDriverState *bs, QDict *options, int flags,
int64_t offset;
int ret;
+ ret = bdrv_apply_auto_read_only(bs, NULL, errp);
+ if (ret < 0) {
+ return ret;
+ }
+
bs->file = bdrv_open_child(NULL, options, "file", bs, &child_file,
false, errp);
if (!bs->file) {
return -EINVAL;
}
- if (!bdrv_is_read_only(bs)) {
- error_report("Opening dmg images without an explicit read-only=on "
- "option is deprecated. Future versions will refuse to "
- "open the image instead of automatically marking the "
- "image read-only.");
- ret = bdrv_set_read_only(bs, true, errp);
- if (ret < 0) {
- return ret;
- }
- }
-
block_module_load_one("dmg-bz2");
s->n_chunks = 0;
diff --git a/block/rbd.c b/block/rbd.c
index 014c68d629..ee0b4a6941 100644
--- a/block/rbd.c
+++ b/block/rbd.c
@@ -780,16 +780,10 @@ static int qemu_rbd_open(BlockDriverState *bs, QDict *options, int flags,
/* If we are using an rbd snapshot, we must be r/o, otherwise
* leave as-is */
if (s->snap != NULL) {
- if (!bdrv_is_read_only(bs)) {
- error_report("Opening rbd snapshots without an explicit "
- "read-only=on option is deprecated. Future versions "
- "will refuse to open the image instead of "
- "automatically marking the image read-only.");
- r = bdrv_set_read_only(bs, true, &local_err);
- if (r < 0) {
- error_propagate(errp, local_err);
- goto failed_open;
- }
+ r = bdrv_apply_auto_read_only(bs, "rbd snapshots are read-only", errp);
+ if (r < 0) {
+ rbd_close(s->image);
+ goto failed_open;
}
}
diff --git a/block/vvfat.c b/block/vvfat.c
index 98ba5e2bac..fd814c39c9 100644
--- a/block/vvfat.c
+++ b/block/vvfat.c
@@ -1262,16 +1262,10 @@ static int vvfat_open(BlockDriverState *bs, QDict *options, int flags,
"Unable to set VVFAT to 'rw' when drive is read-only");
goto fail;
}
- } else if (!bdrv_is_read_only(bs)) {
- error_report("Opening non-rw vvfat images without an explicit "
- "read-only=on option is deprecated. Future versions "
- "will refuse to open the image instead of "
- "automatically marking the image read-only.");
- /* read only is the default for safety */
- ret = bdrv_set_read_only(bs, true, &local_err);
+ } else {
+ ret = bdrv_apply_auto_read_only(bs, NULL, errp);
if (ret < 0) {
- error_propagate(errp, local_err);
- goto fail;
+ return ret;
}
}
--
2.19.1
On 10/12/18 6:55 AM, Kevin Wolf wrote:
> Some block drivers have traditionally changed their node to read-only
> mode without asking the user. This behaviour has been marked deprecated
> since 2.11, expecting users to provide an explicit read-only=on option.
>
> Now that we have auto-read-only=on, enable these drivers to make use of
> the option.
>
> This is the only use of bdrv_set_read_only(), so we can make it a bit
> more specific and turn it into a bdrv_apply_auto_read_only() that is
> more convenient for drivers to use.
>
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> ---
> +++ b/block.c
> @@ -266,27 +266,36 @@ int bdrv_can_set_read_only(BlockDriverState *bs, bool read_only,
> return 0;
> }
>
> -/* TODO Remove (deprecated since 2.11)
> - * Block drivers are not supposed to automatically change bs->read_only.
> - * Instead, they should just check whether they can provide what the user
> - * explicitly requested and error out if read-write is requested, but they can
> - * only provide read-only access. */
> -int bdrv_set_read_only(BlockDriverState *bs, bool read_only, Error **errp)
> +/*
> + * Called by a driver that can only provide a read-only image.
> + *
> + * Returns 0 if the node is already read-only or it could switch the node to
> + * read-only because BDRV_O_AUTO_RDONLY is set.
> + *
> + * Returns -EACCES if the node is read-write and BDRV_O_AUTO_RDONLY is not set.
> + * If @errmsg is not NULL, it is used as the error message for the Error
> + * object.
I like it.
Worth documenting the -EINVAL (copy-on-read prevents setting read-only)
failure as well? (The -EPERM failure of bdrv_can_set_read_only() is not
reachable, since this new function never clears readonly).
> + */
> +int bdrv_apply_auto_read_only(BlockDriverState *bs, const char *errmsg,
> + Error **errp)
> {
> int ret = 0;
>
> - ret = bdrv_can_set_read_only(bs, read_only, false, errp);
> + if (!(bs->open_flags & BDRV_O_RDWR)) {
> + return 0;
> + }
> + if (!(bs->open_flags & BDRV_O_AUTO_RDONLY)) {
> + error_setg(errp, "%s", errmsg ?: "Image is read-only");
> + return -EACCES;
> + }
> +
> + ret = bdrv_can_set_read_only(bs, true, false, errp);
> if (ret < 0) {
> return ret;
> }
Makes sense.
> +++ b/block/vvfat.c
> @@ -1262,16 +1262,10 @@ static int vvfat_open(BlockDriverState *bs, QDict *options, int flags,
> "Unable to set VVFAT to 'rw' when drive is read-only");
> goto fail;
> }
> - } else if (!bdrv_is_read_only(bs)) {
> - error_report("Opening non-rw vvfat images without an explicit "
> - "read-only=on option is deprecated. Future versions "
> - "will refuse to open the image instead of "
> - "automatically marking the image read-only.");
> - /* read only is the default for safety */
> - ret = bdrv_set_read_only(bs, true, &local_err);
> + } else {
> + ret = bdrv_apply_auto_read_only(bs, NULL, errp);
> if (ret < 0) {
> - error_propagate(errp, local_err);
> - goto fail;
> + return ret;
Don't you still need the goto fail, to avoid leaking opts?
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3266
Virtualization: qemu.org | libvirt.org
Am 12.10.2018 um 19:02 hat Eric Blake geschrieben:
> On 10/12/18 6:55 AM, Kevin Wolf wrote:
> > Some block drivers have traditionally changed their node to read-only
> > mode without asking the user. This behaviour has been marked deprecated
> > since 2.11, expecting users to provide an explicit read-only=on option.
> >
> > Now that we have auto-read-only=on, enable these drivers to make use of
> > the option.
> >
> > This is the only use of bdrv_set_read_only(), so we can make it a bit
> > more specific and turn it into a bdrv_apply_auto_read_only() that is
> > more convenient for drivers to use.
> >
> > Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> > ---
>
> > +++ b/block.c
> > @@ -266,27 +266,36 @@ int bdrv_can_set_read_only(BlockDriverState *bs, bool read_only,
> > return 0;
> > }
> > -/* TODO Remove (deprecated since 2.11)
> > - * Block drivers are not supposed to automatically change bs->read_only.
> > - * Instead, they should just check whether they can provide what the user
> > - * explicitly requested and error out if read-write is requested, but they can
> > - * only provide read-only access. */
> > -int bdrv_set_read_only(BlockDriverState *bs, bool read_only, Error **errp)
> > +/*
> > + * Called by a driver that can only provide a read-only image.
> > + *
> > + * Returns 0 if the node is already read-only or it could switch the node to
> > + * read-only because BDRV_O_AUTO_RDONLY is set.
> > + *
> > + * Returns -EACCES if the node is read-write and BDRV_O_AUTO_RDONLY is not set.
> > + * If @errmsg is not NULL, it is used as the error message for the Error
> > + * object.
>
> I like it.
>
> Worth documenting the -EINVAL (copy-on-read prevents setting read-only)
> failure as well? (The -EPERM failure of bdrv_can_set_read_only() is not
> reachable, since this new function never clears readonly).
In fact, -EINVAL and the error string from bdrv_can_set_read_only() may
be confusing because the user didn't explicitly request a read-only
image. Maybe it would be better to just turn this case into -EACCES with
the same error message.
What do you think?
> > + */
> > +int bdrv_apply_auto_read_only(BlockDriverState *bs, const char *errmsg,
> > + Error **errp)
> > {
> > int ret = 0;
> > - ret = bdrv_can_set_read_only(bs, read_only, false, errp);
> > + if (!(bs->open_flags & BDRV_O_RDWR)) {
> > + return 0;
> > + }
> > + if (!(bs->open_flags & BDRV_O_AUTO_RDONLY)) {
> > + error_setg(errp, "%s", errmsg ?: "Image is read-only");
> > + return -EACCES;
> > + }
> > +
> > + ret = bdrv_can_set_read_only(bs, true, false, errp);
> > if (ret < 0) {
> > return ret;
> > }
>
> Makes sense.
>
> > +++ b/block/vvfat.c
> > @@ -1262,16 +1262,10 @@ static int vvfat_open(BlockDriverState *bs, QDict *options, int flags,
> > "Unable to set VVFAT to 'rw' when drive is read-only");
> > goto fail;
> > }
> > - } else if (!bdrv_is_read_only(bs)) {
> > - error_report("Opening non-rw vvfat images without an explicit "
> > - "read-only=on option is deprecated. Future versions "
> > - "will refuse to open the image instead of "
> > - "automatically marking the image read-only.");
> > - /* read only is the default for safety */
> > - ret = bdrv_set_read_only(bs, true, &local_err);
> > + } else {
> > + ret = bdrv_apply_auto_read_only(bs, NULL, errp);
> > if (ret < 0) {
> > - error_propagate(errp, local_err);
> > - goto fail;
> > + return ret;
>
> Don't you still need the goto fail, to avoid leaking opts?
Yes, I do. Thanks.
Kevin
On 10/16/18 9:12 AM, Kevin Wolf wrote: > Am 12.10.2018 um 19:02 hat Eric Blake geschrieben: >> On 10/12/18 6:55 AM, Kevin Wolf wrote: >>> Some block drivers have traditionally changed their node to read-only >>> mode without asking the user. This behaviour has been marked deprecated >>> since 2.11, expecting users to provide an explicit read-only=on option. >>> >>> Now that we have auto-read-only=on, enable these drivers to make use of >>> the option. >>> >>> This is the only use of bdrv_set_read_only(), so we can make it a bit >>> more specific and turn it into a bdrv_apply_auto_read_only() that is >>> more convenient for drivers to use. >>> >>> Signed-off-by: Kevin Wolf <kwolf@redhat.com> >>> --- >> >> Worth documenting the -EINVAL (copy-on-read prevents setting read-only) >> failure as well? (The -EPERM failure of bdrv_can_set_read_only() is not >> reachable, since this new function never clears readonly). > > In fact, -EINVAL and the error string from bdrv_can_set_read_only() may > be confusing because the user didn't explicitly request a read-only > image. Maybe it would be better to just turn this case into -EACCES with > the same error message. > > What do you think? So, how would it trigger in practice? The user requests a copy-on-read action with the BDS as destination (thus the BDS must be writable, and can't be set to readonly); they omitted read-only (because they know they want copy-on-read); they supplied auto-read-only=true (because they are lazy and want to always use that flag if it is available); but the particular BDS they selected is not writable (whether read-only file system, read-only NBD server, etc). In short, we can't grant them read-write to begin with, and can't gracefully fall back to read-only because it would violate their request for copy-on-read, so as long as we give them a sane error message about their request being impossible, we're good. Yes, -EACCES sounds reasonable, if you want to code that in. -- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3266 Virtualization: qemu.org | libvirt.org
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