diff options
author | Pavel Tikhomirov <ptikhomirov@virtuozzo.com> | 2022-05-18 18:25:43 +0300 |
---|---|---|
committer | Andrei Vagin <avagin@gmail.com> | 2022-06-22 20:20:33 +0300 |
commit | 229c5df5cefa4be44305ca08ae20befbb3d0f91d (patch) | |
tree | f7fc4de6e005de2429dab38e7975bf48d74770b8 | |
parent | f8c9e07e4f21685e31a91430da7f1fc55ad36bbb (diff) |
mount-v2: workaround for multiple external bindmounts with no common root
It's a problem when while restoring sharing group we need to copy
sharing between two mounts with non-intersecting roots, because kernel
does not allow it.
We have a case https://github.com/opencontainers/runc/pull/3442, where
runc adds different devtmpfs file-bindmounts to container and there is
no fsroot mount in container for this devtmpfs, thus mount-v2 faces the
above problem.
Luckily for the case of external mounts which are in one sharing group
and which have non-intersecting roots, these mounts likely only have
external master with no sharing, so we can just copy sharing from
external source and make it slave as a workaround.
https://github.com/checkpoint-restore/criu/issues/1886
Signed-off-by: Pavel Tikhomirov <ptikhomirov@virtuozzo.com>
-rw-r--r-- | criu/mount-v2.c | 32 |
1 files changed, 29 insertions, 3 deletions
diff --git a/criu/mount-v2.c b/criu/mount-v2.c index 1d188114f..5d53e9a22 100644 --- a/criu/mount-v2.c +++ b/criu/mount-v2.c @@ -996,9 +996,35 @@ static int restore_one_sharing_group(struct sharing_group *sg) if (other == first) continue; - if (move_mount_set_group(first->mnt_fd_id, NULL, other->mnt_fd_id)) { - pr_err("Failed to copy sharing from %d to %d\n", first->mnt_id, other->mnt_id); - return -1; + if (is_sub_path(other->root, first->root)) { + if (move_mount_set_group(first->mnt_fd_id, NULL, other->mnt_fd_id)) { + pr_err("Failed to copy sharing from %d to %d\n", first->mnt_id, other->mnt_id); + return -1; + } + } else { + /* + * Case where mounts of this sharing group don't have common root. + * For instance we can create two sub-directories .a and .b in some + * shared mount, bindmount them separately somethere and umount the + * original mount. Now we have both bindmounts shared between each + * other. Kernel only allows to copy sharing between mounts when + * source root contains destination root, which is not true for + * these two, so we can't just copy from first to other. + * + * For external sharing (!sg->parent) with only master_id (shared_id + * == 0) we can workaround this by copying from their external source + * instead (same as we did for a first mount). + * + * This is a w/a runc usecase, see https://github.com/opencontainers/runc/pull/3442 + */ + if (!sg->parent && !sg->shared_id) { + if (restore_one_sharing(sg, other)) + return -1; + } else { + pr_err("Can't copy sharing from %d[%s] to %d[%s]\n", first->mnt_id, first->root, + other->mnt_id, other->root); + return -1; + } } } |