From f64042620963059859d0bbae60e8655ccc44736e Mon Sep 17 00:00:00 2001 From: Kevin Wolf Date: Fri, 15 Mar 2019 18:10:01 +0100 Subject: [PATCH 005/163] block: Make permission changes in reopen less wrong RH-Author: Kevin Wolf Message-id: <20190315181010.14964-6-kwolf@redhat.com> Patchwork-id: 84882 O-Subject: [RHEL-7.7 qemu-kvm-rhev PATCH 05/14] block: Make permission changes in reopen less wrong Bugzilla: 1685989 RH-Acked-by: John Snow RH-Acked-by: Stefan Hajnoczi RH-Acked-by: Miroslav Rezanina 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 (cherry picked from commit 69b736e76567ecbc9b9e55570bc0afc840614a98) Signed-off-by: Kevin Wolf Signed-off-by: Miroslav Rezanina --- block.c | 35 ++++++++++++++++++++++++----------- 1 file changed, 24 insertions(+), 11 deletions(-) diff --git a/block.c b/block.c index 2f1b4d1..b31124c 100644 --- a/block.c +++ b/block.c @@ -1661,6 +1661,7 @@ 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; @@ -3072,6 +3073,16 @@ 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 */ @@ -3080,7 +3091,20 @@ 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) { @@ -3297,12 +3321,6 @@ 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; error: @@ -3352,9 +3370,6 @@ 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) { @@ -3386,8 +3401,6 @@ 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); } -- 1.8.3.1