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authorKevin Wolf <kwolf@redhat.com>2019-03-05 17:18:22 +0100
committerKevin Wolf <kwolf@redhat.com>2019-03-12 20:30:14 +0100
commit69b736e76567ecbc9b9e55570bc0afc840614a98 (patch)
tree9785fb617e6e0785f52815d145c3b195b1bc7321 /block.c
parenta4615ab31cade201641cbb17a81dcac1b3bea624 (diff)
block: Make permission changes in reopen less wrong
The way that reopen interacts with permission changes has one big problem: Both operations are recursive, and the permissions are changes for each node in the reopen queue. For a simple graph that consists just of parent and child, .bdrv_check_perm will be called twice for the child, once recursively when adjusting the permissions of parent, and once again when the child itself is reopened. Even worse, the first .bdrv_check_perm call happens before .bdrv_reopen_prepare was called for the child and the second one is called afterwards. Making sure that .bdrv_check_perm (and the other permission callbacks) are called only once is hard. We can cope with multiple calls right now, but as soon as file-posix gets a dynamic auto-read-only that may need to open a new file descriptor, we get the additional requirement that all of them are after the .bdrv_reopen_prepare call. So reorder things in bdrv_reopen_multiple() to first call .bdrv_reopen_prepare for all involved nodes and only then adjust permissions. Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Diffstat (limited to 'block.c')
-rw-r--r--block.c35
1 files changed, 24 insertions, 11 deletions
diff --git a/block.c b/block.c
index e18bd5eefd..9b9d25e843 100644
--- a/block.c
+++ b/block.c
@@ -1698,6 +1698,7 @@ static void bdrv_child_set_perm(BdrvChild *c, uint64_t perm, uint64_t shared);
typedef struct BlockReopenQueueEntry {
bool prepared;
+ bool perms_checked;
BDRVReopenState state;
QSIMPLEQ_ENTRY(BlockReopenQueueEntry) entry;
} BlockReopenQueueEntry;
@@ -3166,6 +3167,16 @@ int bdrv_reopen_multiple(AioContext *ctx, BlockReopenQueue *bs_queue, Error **er
bs_entry->prepared = true;
}
+ QSIMPLEQ_FOREACH(bs_entry, bs_queue, entry) {
+ BDRVReopenState *state = &bs_entry->state;
+ ret = bdrv_check_perm(state->bs, bs_queue, state->perm,
+ state->shared_perm, NULL, errp);
+ if (ret < 0) {
+ goto cleanup_perm;
+ }
+ bs_entry->perms_checked = true;
+ }
+
/* If we reach this point, we have success and just need to apply the
* changes
*/
@@ -3174,7 +3185,20 @@ int bdrv_reopen_multiple(AioContext *ctx, BlockReopenQueue *bs_queue, Error **er
}
ret = 0;
+cleanup_perm:
+ QSIMPLEQ_FOREACH_SAFE(bs_entry, bs_queue, entry, next) {
+ BDRVReopenState *state = &bs_entry->state;
+
+ if (!bs_entry->perms_checked) {
+ continue;
+ }
+ if (ret == 0) {
+ bdrv_set_perm(state->bs, state->perm, state->shared_perm);
+ } else {
+ bdrv_abort_perm_update(state->bs);
+ }
+ }
cleanup:
QSIMPLEQ_FOREACH_SAFE(bs_entry, bs_queue, entry, next) {
if (ret) {
@@ -3428,12 +3452,6 @@ 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;
/* Restore the original reopen_state->options QDict */
@@ -3500,9 +3518,6 @@ 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) {
@@ -3534,8 +3549,6 @@ void bdrv_reopen_abort(BDRVReopenState *reopen_state)
if (drv->bdrv_reopen_abort) {
drv->bdrv_reopen_abort(reopen_state);
}
-
- bdrv_abort_perm_update(reopen_state->bs);
}