diff options
author | Kevin Wolf <kwolf@redhat.com> | 2019-03-05 17:18:22 +0100 |
---|---|---|
committer | Kevin Wolf <kwolf@redhat.com> | 2019-03-12 20:30:14 +0100 |
commit | 69b736e76567ecbc9b9e55570bc0afc840614a98 (patch) | |
tree | 9785fb617e6e0785f52815d145c3b195b1bc7321 /block.c | |
parent | a4615ab31cade201641cbb17a81dcac1b3bea624 (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.c | 35 |
1 files changed, 24 insertions, 11 deletions
@@ -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); } |