Re: [Qemu-devel] [PATCH 6/6] block: Fix permissions after bdrv_reopen()
Am 15.09.2017 um 21:06 hat Eric Blake geschrieben: > On 09/15/2017 05:10 AM, Kevin Wolf wrote: > > If we switch between read-only and read-write, the permissions that > > image format drivers need on bs->file change, too. Make sure to update > > the permissions during bdrv_reopen(). > > > > Signed-off-by: Kevin Wolf> > --- > > include/block/block.h | 1 + > > block.c | 64 > > +++ > > 2 files changed, 65 insertions(+) > > > > > +static BlockReopenQueueEntry *find_parent_in_reopen_queue(BlockReopenQueue > > *q, > > + BdrvChild *c) > > +{ > > +BlockReopenQueueEntry *entry; > > + > > +QSIMPLEQ_FOREACH(entry, q, entry) { > > +BlockDriverState *bs = entry->state.bs; > > +BdrvChild *child; > > + > > +QLIST_FOREACH(child, >children, next) { > > +if (child == c) { > > +return entry; > > An O(n^2) loop. Is it going to bite us at any point in the future, or > are we generally dealing with a small enough queue size and BDS graph to > not worry about it? The loops you're quoting aren't O(n^2), they don't loop over the same thing. This part is O(n) in terms of BdrvChild elements looked at. The thing that worried me a bit more is the caller: +QLIST_FOREACH(c, >parents, next_parent) { +parent = find_parent_in_reopen_queue(q, c); This is indeed O(n^2) (again with n = number of BdrvChild elements) in the pathological worst case of a quorum node where all children point to the same node. As soon as all parents of the node are distinct - and I don't see any reason why they wouldn't in practice - we're back to O(n) because each BdrvChild belongs to only one parent. Even if we ever introduce a driver where having the same node as a child in a constant number of different roles makes sense for a parent (i.e. anything that doesn't involve an (unbounded) array of children), we would still be O(n) with an additional small constant factor. So I think in practice we should be okay. Kevin signature.asc Description: PGP signature
Re: [Qemu-devel] [PATCH 6/6] block: Fix permissions after bdrv_reopen()
Am 18.09.2017 um 09:37 hat Fam Zheng geschrieben: > On Fri, 09/15 12:10, Kevin Wolf wrote: > > If we switch between read-only and read-write, the permissions that > > image format drivers need on bs->file change, too. Make sure to update > > the permissions during bdrv_reopen(). > > > > Signed-off-by: Kevin Wolf> > --- > > include/block/block.h | 1 + > > block.c | 64 > > +++ > > 2 files changed, 65 insertions(+) > > > > diff --git a/include/block/block.h b/include/block/block.h > > index 082eb2cd9c..3c3af462e4 100644 > > --- a/include/block/block.h > > +++ b/include/block/block.h > > @@ -166,6 +166,7 @@ typedef QSIMPLEQ_HEAD(BlockReopenQueue, > > BlockReopenQueueEntry) BlockReopenQueue; > > typedef struct BDRVReopenState { > > BlockDriverState *bs; > > int flags; > > +uint64_t perm, shared_perm; > > QDict *options; > > QDict *explicit_options; > > void *opaque; > > diff --git a/block.c b/block.c > > index 204cbb46c7..5c65fac672 100644 > > --- a/block.c > > +++ b/block.c > > @@ -2781,6 +2781,10 @@ static BlockReopenQueue > > *bdrv_reopen_queue_child(BlockReopenQueue *bs_queue, > > bs_entry->state.explicit_options = explicit_options; > > bs_entry->state.flags = flags; > > > > +/* This needs to be overwritten in bdrv_reopen_prepare() */ > > +bs_entry->state.perm = UINT64_MAX; > > Probably doesn't matter because as the comment says it will be overwritten > soon, > but is BLK_PERM_ALL more appropriate? I had BLK_PERM_ALL at first, but after debugging some assertion failures in gdb, I came to the conclusion that UINT64_MAX is easier to identify as uninitialised than BLK_PERM_ALL, which could be a valid result of the permission calculation. Kevin
Re: [Qemu-devel] [PATCH 6/6] block: Fix permissions after bdrv_reopen()
On Fri, 09/15 12:10, Kevin Wolf wrote: > If we switch between read-only and read-write, the permissions that > image format drivers need on bs->file change, too. Make sure to update > the permissions during bdrv_reopen(). > > Signed-off-by: Kevin Wolf> --- > include/block/block.h | 1 + > block.c | 64 > +++ > 2 files changed, 65 insertions(+) > > diff --git a/include/block/block.h b/include/block/block.h > index 082eb2cd9c..3c3af462e4 100644 > --- a/include/block/block.h > +++ b/include/block/block.h > @@ -166,6 +166,7 @@ typedef QSIMPLEQ_HEAD(BlockReopenQueue, > BlockReopenQueueEntry) BlockReopenQueue; > typedef struct BDRVReopenState { > BlockDriverState *bs; > int flags; > +uint64_t perm, shared_perm; > QDict *options; > QDict *explicit_options; > void *opaque; > diff --git a/block.c b/block.c > index 204cbb46c7..5c65fac672 100644 > --- a/block.c > +++ b/block.c > @@ -2781,6 +2781,10 @@ static BlockReopenQueue > *bdrv_reopen_queue_child(BlockReopenQueue *bs_queue, > bs_entry->state.explicit_options = explicit_options; > bs_entry->state.flags = flags; > > +/* This needs to be overwritten in bdrv_reopen_prepare() */ > +bs_entry->state.perm = UINT64_MAX; Probably doesn't matter because as the comment says it will be overwritten soon, but is BLK_PERM_ALL more appropriate? > +bs_entry->state.shared_perm = 0; > + > QLIST_FOREACH(child, >children, next) { > QDict *new_child_options; > char *child_key_dot; > @@ -2887,6 +2891,52 @@ int bdrv_reopen(BlockDriverState *bs, int bdrv_flags, > Error **errp) > return ret; > } > > +static BlockReopenQueueEntry *find_parent_in_reopen_queue(BlockReopenQueue > *q, > + BdrvChild *c) > +{ > +BlockReopenQueueEntry *entry; > + > +QSIMPLEQ_FOREACH(entry, q, entry) { > +BlockDriverState *bs = entry->state.bs; > +BdrvChild *child; > + > +QLIST_FOREACH(child, >children, next) { > +if (child == c) { > +return entry; > +} > +} > +} > + > +return NULL; > +} > + > +static void bdrv_reopen_perm(BlockReopenQueue *q, BlockDriverState *bs, > + uint64_t *perm, uint64_t *shared) > +{ > +BdrvChild *c; > +BlockReopenQueueEntry *parent; > +uint64_t cumulative_perms = 0; > +uint64_t cumulative_shared_perms = BLK_PERM_ALL; > + > +QLIST_FOREACH(c, >parents, next_parent) { > +parent = find_parent_in_reopen_queue(q, c); > +if (!parent) { > +cumulative_perms |= c->perm; > +cumulative_shared_perms &= c->shared_perm; > +} else { > +uint64_t nperm, nshared; > + > +bdrv_child_perm(parent->state.bs, bs, c, c->role, q, > +parent->state.perm, parent->state.shared_perm, > +, ); > + > +cumulative_perms |= nperm; > +cumulative_shared_perms &= nshared; > +} > +} > +*perm = cumulative_perms; > +*shared = cumulative_shared_perms; > +} > > /* > * Prepares a BlockDriverState for reopen. All changes are staged in the > @@ -2952,6 +3002,9 @@ int bdrv_reopen_prepare(BDRVReopenState *reopen_state, > BlockReopenQueue *queue, > goto error; > } > > +/* Calculate required permissions after reopening */ > +bdrv_reopen_perm(queue, reopen_state->bs, > + _state->perm, _state->shared_perm); > > ret = bdrv_flush(reopen_state->bs); > if (ret) { > @@ -3007,6 +3060,12 @@ int bdrv_reopen_prepare(BDRVReopenState *reopen_state, > BlockReopenQueue *queue, > } while ((entry = qdict_next(reopen_state->options, entry))); > } > > +ret = bdrv_check_perm(reopen_state->bs, queue, reopen_state->perm, > + reopen_state->shared_perm, NULL, errp); > +if (ret < 0) { > +goto error; > +} > + > ret = 0; > > error: > @@ -3047,6 +3106,9 @@ void bdrv_reopen_commit(BDRVReopenState *reopen_state) > > bdrv_refresh_limits(bs, NULL); > > +bdrv_set_perm(reopen_state->bs, reopen_state->perm, > + reopen_state->shared_perm); > + > new_can_write = > !bdrv_is_read_only(bs) && !(bdrv_get_flags(bs) & BDRV_O_INACTIVE); > if (!old_can_write && new_can_write && drv->bdrv_reopen_bitmaps_rw) { > @@ -3080,6 +3142,8 @@ void bdrv_reopen_abort(BDRVReopenState *reopen_state) > } > > QDECREF(reopen_state->explicit_options); > + > +bdrv_abort_perm_update(reopen_state->bs); > } > > > -- > 2.13.5 >
Re: [Qemu-devel] [PATCH 6/6] block: Fix permissions after bdrv_reopen()
On 09/15/2017 05:10 AM, Kevin Wolf wrote: > If we switch between read-only and read-write, the permissions that > image format drivers need on bs->file change, too. Make sure to update > the permissions during bdrv_reopen(). > > Signed-off-by: Kevin Wolf> --- > include/block/block.h | 1 + > block.c | 64 > +++ > 2 files changed, 65 insertions(+) > > +static BlockReopenQueueEntry *find_parent_in_reopen_queue(BlockReopenQueue > *q, > + BdrvChild *c) > +{ > +BlockReopenQueueEntry *entry; > + > +QSIMPLEQ_FOREACH(entry, q, entry) { > +BlockDriverState *bs = entry->state.bs; > +BdrvChild *child; > + > +QLIST_FOREACH(child, >children, next) { > +if (child == c) { > +return entry; An O(n^2) loop. Is it going to bite us at any point in the future, or are we generally dealing with a small enough queue size and BDS graph to not worry about it? Reviewed-by: Eric Blake -- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3266 Virtualization: qemu.org | libvirt.org signature.asc Description: OpenPGP digital signature
[Qemu-devel] [PATCH 6/6] block: Fix permissions after bdrv_reopen()
If we switch between read-only and read-write, the permissions that image format drivers need on bs->file change, too. Make sure to update the permissions during bdrv_reopen(). Signed-off-by: Kevin Wolf--- include/block/block.h | 1 + block.c | 64 +++ 2 files changed, 65 insertions(+) diff --git a/include/block/block.h b/include/block/block.h index 082eb2cd9c..3c3af462e4 100644 --- a/include/block/block.h +++ b/include/block/block.h @@ -166,6 +166,7 @@ typedef QSIMPLEQ_HEAD(BlockReopenQueue, BlockReopenQueueEntry) BlockReopenQueue; typedef struct BDRVReopenState { BlockDriverState *bs; int flags; +uint64_t perm, shared_perm; QDict *options; QDict *explicit_options; void *opaque; diff --git a/block.c b/block.c index 204cbb46c7..5c65fac672 100644 --- a/block.c +++ b/block.c @@ -2781,6 +2781,10 @@ static BlockReopenQueue *bdrv_reopen_queue_child(BlockReopenQueue *bs_queue, bs_entry->state.explicit_options = explicit_options; bs_entry->state.flags = flags; +/* This needs to be overwritten in bdrv_reopen_prepare() */ +bs_entry->state.perm = UINT64_MAX; +bs_entry->state.shared_perm = 0; + QLIST_FOREACH(child, >children, next) { QDict *new_child_options; char *child_key_dot; @@ -2887,6 +2891,52 @@ int bdrv_reopen(BlockDriverState *bs, int bdrv_flags, Error **errp) return ret; } +static BlockReopenQueueEntry *find_parent_in_reopen_queue(BlockReopenQueue *q, + BdrvChild *c) +{ +BlockReopenQueueEntry *entry; + +QSIMPLEQ_FOREACH(entry, q, entry) { +BlockDriverState *bs = entry->state.bs; +BdrvChild *child; + +QLIST_FOREACH(child, >children, next) { +if (child == c) { +return entry; +} +} +} + +return NULL; +} + +static void bdrv_reopen_perm(BlockReopenQueue *q, BlockDriverState *bs, + uint64_t *perm, uint64_t *shared) +{ +BdrvChild *c; +BlockReopenQueueEntry *parent; +uint64_t cumulative_perms = 0; +uint64_t cumulative_shared_perms = BLK_PERM_ALL; + +QLIST_FOREACH(c, >parents, next_parent) { +parent = find_parent_in_reopen_queue(q, c); +if (!parent) { +cumulative_perms |= c->perm; +cumulative_shared_perms &= c->shared_perm; +} else { +uint64_t nperm, nshared; + +bdrv_child_perm(parent->state.bs, bs, c, c->role, q, +parent->state.perm, parent->state.shared_perm, +, ); + +cumulative_perms |= nperm; +cumulative_shared_perms &= nshared; +} +} +*perm = cumulative_perms; +*shared = cumulative_shared_perms; +} /* * Prepares a BlockDriverState for reopen. All changes are staged in the @@ -2952,6 +3002,9 @@ int bdrv_reopen_prepare(BDRVReopenState *reopen_state, BlockReopenQueue *queue, goto error; } +/* Calculate required permissions after reopening */ +bdrv_reopen_perm(queue, reopen_state->bs, + _state->perm, _state->shared_perm); ret = bdrv_flush(reopen_state->bs); if (ret) { @@ -3007,6 +3060,12 @@ int bdrv_reopen_prepare(BDRVReopenState *reopen_state, BlockReopenQueue *queue, } while ((entry = qdict_next(reopen_state->options, entry))); } +ret = bdrv_check_perm(reopen_state->bs, queue, reopen_state->perm, + reopen_state->shared_perm, NULL, errp); +if (ret < 0) { +goto error; +} + ret = 0; error: @@ -3047,6 +3106,9 @@ void bdrv_reopen_commit(BDRVReopenState *reopen_state) bdrv_refresh_limits(bs, NULL); +bdrv_set_perm(reopen_state->bs, reopen_state->perm, + reopen_state->shared_perm); + new_can_write = !bdrv_is_read_only(bs) && !(bdrv_get_flags(bs) & BDRV_O_INACTIVE); if (!old_can_write && new_can_write && drv->bdrv_reopen_bitmaps_rw) { @@ -3080,6 +3142,8 @@ void bdrv_reopen_abort(BDRVReopenState *reopen_state) } QDECREF(reopen_state->explicit_options); + +bdrv_abort_perm_update(reopen_state->bs); } -- 2.13.5