})
typedef enum DissectImageFlags {
- DISSECT_IMAGE_DEVICE_READ_ONLY = 1 << 0, /* Make device read-only */
- DISSECT_IMAGE_DISCARD_ON_LOOP = 1 << 1, /* Turn on "discard" if on a loop device and file system supports it */
- DISSECT_IMAGE_DISCARD = 1 << 2, /* Turn on "discard" if file system supports it, on all block devices */
- DISSECT_IMAGE_DISCARD_ON_CRYPTO = 1 << 3, /* Turn on "discard" also on crypto devices */
- DISSECT_IMAGE_DISCARD_ANY = DISSECT_IMAGE_DISCARD_ON_LOOP |
- DISSECT_IMAGE_DISCARD |
- DISSECT_IMAGE_DISCARD_ON_CRYPTO,
- DISSECT_IMAGE_GPT_ONLY = 1 << 4, /* Only recognize images with GPT partition tables */
- DISSECT_IMAGE_GENERIC_ROOT = 1 << 5, /* If no partition table or only single generic partition, assume it's the root fs */
- DISSECT_IMAGE_MOUNT_ROOT_ONLY = 1 << 6, /* Mount only the root and /usr partitions */
- DISSECT_IMAGE_MOUNT_NON_ROOT_ONLY = 1 << 7, /* Mount only the non-root and non-/usr partitions */
- DISSECT_IMAGE_VALIDATE_OS = 1 << 8, /* Refuse mounting images that aren't identifiable as OS images */
- DISSECT_IMAGE_VALIDATE_OS_EXT = 1 << 9, /* Refuse mounting images that aren't identifiable as OS extension images */
- DISSECT_IMAGE_RELAX_VAR_CHECK = 1 << 10, /* Don't insist that the UUID of /var is hashed from /etc/machine-id */
- DISSECT_IMAGE_FSCK = 1 << 11, /* File system check the partition before mounting (no effect when combined with DISSECT_IMAGE_READ_ONLY) */
- DISSECT_IMAGE_NO_PARTITION_TABLE = 1 << 12, /* Only recognize single file system images */
- DISSECT_IMAGE_VERITY_SHARE = 1 << 13, /* When activating a verity device, reuse existing one if already open */
- DISSECT_IMAGE_MKDIR = 1 << 14, /* Make top-level directory to mount right before mounting, if missing */
- DISSECT_IMAGE_USR_NO_ROOT = 1 << 15, /* If no root fs is in the image, but /usr is, then allow this (so that we can mount the rootfs as tmpfs or so */
- DISSECT_IMAGE_REQUIRE_ROOT = 1 << 16, /* Don't accept disks without root partition (or at least /usr partition if DISSECT_IMAGE_USR_NO_ROOT is set) */
- DISSECT_IMAGE_MOUNT_READ_ONLY = 1 << 17, /* Make mounts read-only */
- DISSECT_IMAGE_READ_ONLY = DISSECT_IMAGE_DEVICE_READ_ONLY |
- DISSECT_IMAGE_MOUNT_READ_ONLY,
- DISSECT_IMAGE_GROWFS = 1 << 18, /* Grow file systems in partitions marked for that to the size of the partitions after mount */
- DISSECT_IMAGE_MOUNT_IDMAPPED = 1 << 19, /* Mount mounts with kernel 5.12-style userns ID mapping, if file system type doesn't support uid=/gid= */
- DISSECT_IMAGE_ADD_PARTITION_DEVICES = 1 << 20, /* Create partition devices via BLKPG_ADD_PARTITION */
- DISSECT_IMAGE_PIN_PARTITION_DEVICES = 1 << 21, /* Open dissected partitions and decrypted partitions and pin them by fd */
- DISSECT_IMAGE_RELAX_EXTENSION_CHECK = 1 << 22, /* Don't insist that the extension-release file name matches the image name */
- DISSECT_IMAGE_DISKSEQ_DEVNODE = 1 << 23, /* Prefer /dev/disk/by-diskseq/… device nodes */
- DISSECT_IMAGE_ALLOW_EMPTY = 1 << 24, /* Allow that no usable partitions is present */
+ DISSECT_IMAGE_DEVICE_READ_ONLY = 1 << 0, /* Make device read-only */
+ DISSECT_IMAGE_DISCARD_ON_LOOP = 1 << 1, /* Turn on "discard" if on a loop device and file system supports it */
+ DISSECT_IMAGE_DISCARD = 1 << 2, /* Turn on "discard" if file system supports it, on all block devices */
+ DISSECT_IMAGE_DISCARD_ON_CRYPTO = 1 << 3, /* Turn on "discard" also on crypto devices */
+ DISSECT_IMAGE_DISCARD_ANY = DISSECT_IMAGE_DISCARD_ON_LOOP |
+ DISSECT_IMAGE_DISCARD |
+ DISSECT_IMAGE_DISCARD_ON_CRYPTO,
+ DISSECT_IMAGE_GPT_ONLY = 1 << 4, /* Only recognize images with GPT partition tables */
+ DISSECT_IMAGE_GENERIC_ROOT = 1 << 5, /* If no partition table or only single generic partition, assume it's the root fs */
+ DISSECT_IMAGE_MOUNT_ROOT_ONLY = 1 << 6, /* Mount only the root and /usr partitions */
+ DISSECT_IMAGE_MOUNT_NON_ROOT_ONLY = 1 << 7, /* Mount only the non-root and non-/usr partitions */
+ DISSECT_IMAGE_VALIDATE_OS = 1 << 8, /* Refuse mounting images that aren't identifiable as OS images */
+ DISSECT_IMAGE_VALIDATE_OS_EXT = 1 << 9, /* Refuse mounting images that aren't identifiable as OS extension images */
+ DISSECT_IMAGE_RELAX_VAR_CHECK = 1 << 10, /* Don't insist that the UUID of /var is hashed from /etc/machine-id */
+ DISSECT_IMAGE_FSCK = 1 << 11, /* File system check the partition before mounting (no effect when combined with DISSECT_IMAGE_READ_ONLY) */
+ DISSECT_IMAGE_NO_PARTITION_TABLE = 1 << 12, /* Only recognize single file system images */
+ DISSECT_IMAGE_VERITY_SHARE = 1 << 13, /* When activating a verity device, reuse existing one if already open */
+ DISSECT_IMAGE_MKDIR = 1 << 14, /* Make top-level directory to mount right before mounting, if missing */
+ DISSECT_IMAGE_USR_NO_ROOT = 1 << 15, /* If no root fs is in the image, but /usr is, then allow this (so that we can mount the rootfs as tmpfs or so */
+ DISSECT_IMAGE_REQUIRE_ROOT = 1 << 16, /* Don't accept disks without root partition (or at least /usr partition if DISSECT_IMAGE_USR_NO_ROOT is set) */
+ DISSECT_IMAGE_MOUNT_READ_ONLY = 1 << 17, /* Make mounts read-only */
+ DISSECT_IMAGE_READ_ONLY = DISSECT_IMAGE_DEVICE_READ_ONLY |
+ DISSECT_IMAGE_MOUNT_READ_ONLY,
+ DISSECT_IMAGE_GROWFS = 1 << 18, /* Grow file systems in partitions marked for that to the size of the partitions after mount */
+ DISSECT_IMAGE_MOUNT_IDMAPPED = 1 << 19, /* Mount mounts with kernel 5.12-style userns ID mapping, if file system type doesn't support uid=/gid= */
+ DISSECT_IMAGE_ADD_PARTITION_DEVICES = 1 << 20, /* Create partition devices via BLKPG_ADD_PARTITION */
+ DISSECT_IMAGE_PIN_PARTITION_DEVICES = 1 << 21, /* Open dissected partitions and decrypted partitions and pin them by fd */
+ DISSECT_IMAGE_RELAX_EXTENSION_CHECK = 1 << 22, /* Don't insist that the extension-release file name matches the image name */
+ DISSECT_IMAGE_DISKSEQ_DEVNODE = 1 << 23, /* Prefer /dev/disk/by-diskseq/… device nodes */
+ DISSECT_IMAGE_ALLOW_EMPTY = 1 << 24, /* Allow that no usable partitions is present */
+ DISSECT_IMAGE_TRY_ATOMIC_MOUNT_EXCHANGE = 1 << 25, /* Try to mount the image beneath the specified mountpoint, rather than on top of it, and then umount the top */
} DissectImageFlags;
struct DissectedImage {
return 0;
}
+int mount_exchange_graceful(int fsmount_fd, const char *dest, bool mount_beneath) {
+ int r;
+
+ assert(fsmount_fd >= 0);
+ assert(dest);
+
+ /* First, try to mount beneath an existing mount point, and if that works, umount the old mount,
+ * which is now at the top. This will ensure we can atomically replace a mount. Note that this works
+ * also in the case where there are submounts down the tree. Mount propagation is allowed but
+ * restricted to layouts that don't end up propagation the new mount on top of the mount stack. If
+ * this is not supported (minimum kernel v6.5), or if there is no mount on the mountpoint, we get
+ * -EINVAL and then we fallback to normal mounting. */
+
+ r = RET_NERRNO(move_mount(
+ fsmount_fd,
+ /* from_path= */ "",
+ /* to_fd= */ -EBADF,
+ dest,
+ MOVE_MOUNT_F_EMPTY_PATH | (mount_beneath ? MOVE_MOUNT_BENEATH : 0)));
+ if (mount_beneath) {
+ if (r == -EINVAL) { /* Fallback if mount_beneath is not supported */
+ log_debug_errno(r,
+ "Failed to mount beneath '%s', falling back to overmount",
+ dest);
+ return RET_NERRNO(move_mount(
+ fsmount_fd,
+ /* from_path= */ "",
+ /* to_fd= */ -EBADF,
+ dest,
+ MOVE_MOUNT_F_EMPTY_PATH));
+ }
+
+ if (r >= 0) /* If it is, now remove the old mount */
+ return umount_verbose(LOG_DEBUG, dest, UMOUNT_NOFOLLOW|MNT_DETACH);
+ }
+
+ return r;
+}
+
int mount_option_mangle(
const char *options,
unsigned long mount_flags,
(void) mkdir_parents(dest, 0755);
if (img) {
- DissectImageFlags f = 0;
+ DissectImageFlags f = DISSECT_IMAGE_TRY_ATOMIC_MOUNT_EXCHANGE;
if (make_file_or_directory)
f |= DISSECT_IMAGE_MKDIR;
if (make_file_or_directory)
(void) make_mount_point_inode_from_stat(&st, dest, 0700);
- r = RET_NERRNO(move_mount(new_mount_fd,
- "",
- -EBADF,
- dest,
- MOVE_MOUNT_F_EMPTY_PATH));
+ r = mount_exchange_graceful(new_mount_fd, dest, /* mount_beneath= */ true);
}
if (r < 0) {
(void) write(errno_pipe_fd[1], &r, sizeof(r));
projects / thirdparty / systemd.git / commitdiff
