Le Wednesday 04 Dec 2013 à 11:35:51 (+0800), Fam Zheng a écrit :
> On 2013年12月03日 21:26, Benoît Canet wrote:
> >---
> > block.c | 64
> > +++++++++++++++++++++++++++++++++++++++++------
> > block/blkverify.c | 2 +-
> > include/block/block.h | 16 +++++++++---
> > include/block/block_int.h | 9 ++++---
> > 4 files changed, 75 insertions(+), 16 deletions(-)
> >
> >diff --git a/block.c b/block.c
> >index 8016ff2..0569cb2 100644
> >--- a/block.c
> >+++ b/block.c
> >@@ -4945,21 +4945,69 @@ int bdrv_amend_options(BlockDriverState *bs,
> >QEMUOptionParameter *options)
> > return bs->drv->bdrv_amend_options(bs, options);
> > }
> >
> >-ExtSnapshotPerm bdrv_check_ext_snapshot(BlockDriverState *bs)
> >+/* will be used to recurse on single child block filter until first format
> >+ * (single child block filter will store their child in bs->file)
> >+ */
> >+ExtSnapshotPerm bdrv_generic_check_ext_snapshot(BlockDriverState *bs,
> >+ BlockDriverState *candidate)
> > {
> >- if (bs->drv->bdrv_check_ext_snapshot) {
> >- return bs->drv->bdrv_check_ext_snapshot(bs);
> >+ if (!bs->drv) {
> >+ return EXT_SNAPSHOT_FORBIDDEN;
> > }
> >
> >- if (bs->file && bs->file->drv &&
> >bs->file->drv->bdrv_check_ext_snapshot) {
> >- return bs->file->drv->bdrv_check_ext_snapshot(bs);
> >+ if (!bs->drv->authorizations[BS_CANT_SNAPSHOT]) {
> >+ if (bs == candidate) {
> >+ return EXT_SNAPSHOT_ALLOWED;
> >+ } else {
> >+ return EXT_SNAPSHOT_FORBIDDEN;
> >+ }
> > }
> >
> >- /* external snapshots are allowed by default */
> >- return EXT_SNAPSHOT_ALLOWED;
> >+ if (!bs->drv->authorizations[BS_FILTER_PASS_DOWN]) {
> >+ return EXT_SNAPSHOT_FORBIDDEN;
> >+ }
> >+
> >+ if (!bs->file) {
> >+ return EXT_SNAPSHOT_FORBIDDEN;
> >+ }
> >+
> >+ return bdrv_recurse_check_ext_snapshot(bs->file, candidate);
> > }
> >
> >-ExtSnapshotPerm bdrv_check_ext_snapshot_forbidden(BlockDriverState *bs)
> >+ExtSnapshotPerm bdrv_recurse_check_ext_snapshot(BlockDriverState *bs,
> >+ BlockDriverState *candidate)
> > {
> >+ if (bs->drv && bs->drv->bdrv_check_ext_snapshot) {
> >+ return bs->drv->bdrv_check_ext_snapshot(bs, candidate);
> >+ }
> >+
> >+ return bdrv_generic_check_ext_snapshot(bs, candidate);
> >+}
> >+
> >+/* This function check if the candidate bs has snapshots authorized by going
> >+ * down the forest of bs, skipping filters and stopping on the the first
> >bses
> >+ * authorizing snapshots
> >+ */
> >+ExtSnapshotPerm bdrv_check_ext_snapshot(BlockDriverState *candidate)
> >+{
> >+ BlockDriverState *bs;
> >+
> >+ /* walk down the bs forest recursively */
> >+ QTAILQ_FOREACH(bs, &bdrv_states, device_list) {
> >+ ExtSnapshotPerm perm;
> >+
> >+ if (!bs->file) {
> >+ continue;
> >+ }
> >+
> >+ perm = bdrv_recurse_check_ext_snapshot(bs->file, candidate);
> >+
> >+ /* allowed in the right subtree -> stop here */
> >+ if (perm == EXT_SNAPSHOT_ALLOWED) {
> >+ return EXT_SNAPSHOT_ALLOWED;
> >+ }
> >+ }
> >+
> >+ /* external snapshots are forbidden by default */
> > return EXT_SNAPSHOT_FORBIDDEN;
> > }
> >diff --git a/block/blkverify.c b/block/blkverify.c
> >index e755e4e..b93017c 100644
> >--- a/block/blkverify.c
> >+++ b/block/blkverify.c
> >@@ -313,7 +313,7 @@ static BlockDriver bdrv_blkverify = {
> > .bdrv_aio_writev = blkverify_aio_writev,
> > .bdrv_aio_flush = blkverify_aio_flush,
> >
> >- .bdrv_check_ext_snapshot = bdrv_check_ext_snapshot_forbidden,
> >+ .authorizations = { true, false },
> > };
> >
> > static void bdrv_blkverify_init(void)
> >diff --git a/include/block/block.h b/include/block/block.h
> >index 26c48e7..73c59fe 100644
> >--- a/include/block/block.h
> >+++ b/include/block/block.h
> >@@ -280,16 +280,24 @@ int bdrv_amend_options(BlockDriverState *bs_new,
> >QEMUOptionParameter *options);
> > /* external snapshots */
> >
> > typedef enum {
> >- EXT_SNAPSHOT_ALLOWED,
> > EXT_SNAPSHOT_FORBIDDEN,
> >+ EXT_SNAPSHOT_ALLOWED,
> > } ExtSnapshotPerm;
> >
> >+typedef enum {
> >+ BS_CANT_SNAPSHOT,
> >+ BS_FILTER_PASS_DOWN,
> >+ BS_AUTHORIZATION_COUNT,
> >+} BsAuthorization;
> >+
> > /* return EXT_SNAPSHOT_ALLOWED if external snapshot is allowed
> > * return EXT_SNAPSHOT_FORBIDDEN if external snapshot is forbidden
> > */
> >-ExtSnapshotPerm bdrv_check_ext_snapshot(BlockDriverState *bs);
> >-/* helper used to forbid external snapshots like in blkverify */
> >-ExtSnapshotPerm bdrv_check_ext_snapshot_forbidden(BlockDriverState *bs);
> >+ExtSnapshotPerm bdrv_generic_check_ext_snapshot(BlockDriverState *bs,
> >+ BlockDriverState
> >*candidate);
> >+ExtSnapshotPerm bdrv_recurse_check_ext_snapshot(BlockDriverState *bs,
> >+ BlockDriverState
> >*candidate);
> >+ExtSnapshotPerm bdrv_check_ext_snapshot(BlockDriverState *candidate);
> >
> > /* async block I/O */
> > typedef void BlockDriverDirtyHandler(BlockDriverState *bs, int64_t sector,
> >diff --git a/include/block/block_int.h b/include/block/block_int.h
> >index 9e789d2..d9704f2 100644
> >--- a/include/block/block_int.h
> >+++ b/include/block/block_int.h
> >@@ -69,10 +69,13 @@ struct BlockDriver {
> > const char *format_name;
> > int instance_size;
> >
> >- /* if not defined external snapshots are allowed
> >- * future block filters will query their children to build the response
> >+ /* this table of boolean contains authorizations for the block
> >operations */
> >+ bool authorizations[BS_AUTHORIZATION_COUNT];
>
> OK, I see some overlap of work here with my image fleecing patch series:
>
> http://lists.gnu.org/archive/html/qemu-devel/2013-11/msg03694.html
>
> The disadvantage of using a bool array is that it can't keep track
> of multiple points in code that want to forbid the same operation.
> So I think an array of int is better here.
>
> And what do you think of my posted interface, does it works for you?
Your is in BlockDriverState mine is in BlockDriver so there are not compatible.
I think we need to get advice from other people.
Best regards
Benoît
>
> Fam
>
> >+ /* future complex block filters will implement the following to query
> >their
> >+ * children to check if snapshoting is allowed on a bs of the graph
> > */
> >- ExtSnapshotPerm (*bdrv_check_ext_snapshot)(BlockDriverState *bs);
> >+ ExtSnapshotPerm (*bdrv_check_ext_snapshot)(BlockDriverState *bs,
> >+ BlockDriverState *candidate);
> >
> > int (*bdrv_probe)(const uint8_t *buf, int buf_size, const char
> > *filename);
> > int (*bdrv_probe_device)(const char *filename);
> >
>
>
