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block: Require auto-read-only for existing fallbacks 

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>
Reviewed-by: Eric Blake <eblake@redhat.com>
This commit is contained in:
Kevin Wolf 2018-10-12 11:27:41 +02:00
parent a51b9c4862
commit eaa2410f1e
7 changed files with 51 additions and 68 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

42
block.c
View File

@ -266,29 +266,41 @@ 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
* or bdrv_can_set_read_only() forbids making the node read-only. 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)) {
goto fail;
}
ret = bdrv_can_set_read_only(bs, true, false, NULL);
if (ret < 0) {
return ret;
goto fail;
}
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;
fail:
error_setg(errp, "%s", errmsg ?: "Image is read-only");
return -EACCES;
}
void bdrv_get_full_backing_filename_from_filename(const char *backed,

17
block/bochs.c
View File

@ -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;

16
block/cloop.c
View File

@ -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) {

16
block/dmg.c
View File

@ -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;

15
block/rbd.c
View File

@ -780,17 +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) {
rbd_close(s->image);
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;
}
}

10
block/vvfat.c
View File

@ -1262,15 +1262,9 @@ 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;
}
}

3
include/block/block.h
View File

@ -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);