From ef0698793cd19e82ce8e94e89f1c6461ec2f1dce Mon Sep 17 00:00:00 2001 From: Lennart Poettering Date: Mon, 6 Apr 2015 15:26:59 +0200 Subject: [PATCH 1/1] btrfs: add support for recursive btrfs snapshotting --- src/shared/btrfs-util.c | 248 +++++++++++++++++++++++++++---------- src/shared/btrfs-util.h | 1 + src/shared/machine-image.c | 2 +- 3 files changed, 182 insertions(+), 69 deletions(-) diff --git a/src/shared/btrfs-util.c b/src/shared/btrfs-util.c index 7fb92b22e..5bf87a389 100644 --- a/src/shared/btrfs-util.c +++ b/src/shared/btrfs-util.c @@ -101,74 +101,6 @@ int btrfs_is_snapshot(int fd) { return F_TYPE_EQUAL(sfs.f_type, BTRFS_SUPER_MAGIC); } -int btrfs_subvol_snapshot_fd(int old_fd, const char *new_path, BtrfsSnapshotFlags flags) { - struct btrfs_ioctl_vol_args_v2 args = { - .flags = flags & BTRFS_SNAPSHOT_READ_ONLY ? BTRFS_SUBVOL_RDONLY : 0, - }; - _cleanup_close_ int new_fd = -1; - const char *subvolume; - int r; - - assert(new_path); - - r = btrfs_is_snapshot(old_fd); - if (r < 0) - return r; - if (r == 0) { - if (!(flags & BTRFS_SNAPSHOT_FALLBACK_COPY)) - return -EISDIR; - - r = btrfs_subvol_make(new_path); - if (r < 0) - return r; - - r = copy_directory_fd(old_fd, new_path, true); - if (r < 0) { - btrfs_subvol_remove(new_path, false); - return r; - } - - if (flags & BTRFS_SNAPSHOT_READ_ONLY) { - r = btrfs_subvol_set_read_only(new_path, true); - if (r < 0) { - btrfs_subvol_remove(new_path, false); - return r; - } - } - - return 0; - } - - r = extract_subvolume_name(new_path, &subvolume); - if (r < 0) - return r; - - new_fd = open_parent(new_path, O_RDONLY|O_NOCTTY|O_CLOEXEC|O_DIRECTORY); - if (new_fd < 0) - return new_fd; - - strncpy(args.name, subvolume, sizeof(args.name)-1); - args.fd = old_fd; - - if (ioctl(new_fd, BTRFS_IOC_SNAP_CREATE_V2, &args) < 0) - return -errno; - - return 0; -} - -int btrfs_subvol_snapshot(const char *old_path, const char *new_path, BtrfsSnapshotFlags flags) { - _cleanup_close_ int old_fd = -1; - - assert(old_path); - assert(new_path); - - old_fd = open(old_path, O_RDONLY|O_NOCTTY|O_CLOEXEC|O_DIRECTORY); - if (old_fd < 0) - return -errno; - - return btrfs_subvol_snapshot_fd(old_fd, new_path, flags); -} - int btrfs_subvol_make(const char *path) { struct btrfs_ioctl_vol_args args = {}; _cleanup_close_ int fd = -1; @@ -909,3 +841,183 @@ int btrfs_subvol_remove(const char *path, bool recursive) { int btrfs_subvol_remove_fd(int fd, const char *subvolume, bool recursive) { return subvol_remove_children(fd, subvolume, 0, recursive); } + +static int subvol_snapshot_children(int old_fd, int new_fd, const char *subvolume, uint64_t subvol_id, BtrfsSnapshotFlags flags) { + + struct btrfs_ioctl_search_args args = { + .key.tree_id = BTRFS_ROOT_TREE_OBJECTID, + + .key.min_objectid = BTRFS_FIRST_FREE_OBJECTID, + .key.max_objectid = BTRFS_LAST_FREE_OBJECTID, + + .key.min_type = BTRFS_ROOT_BACKREF_KEY, + .key.max_type = BTRFS_ROOT_BACKREF_KEY, + + .key.min_transid = 0, + .key.max_transid = (uint64_t) -1, + }; + + struct btrfs_ioctl_vol_args_v2 vol_args = { + .flags = flags & BTRFS_SNAPSHOT_READ_ONLY ? BTRFS_SUBVOL_RDONLY : 0, + .fd = old_fd, + }; + int r; + + assert(old_fd >= 0); + assert(new_fd >= 0); + assert(subvolume); + + strncpy(vol_args.name, subvolume, sizeof(vol_args.name)-1); + vol_args.fd = old_fd; + + if (ioctl(new_fd, BTRFS_IOC_SNAP_CREATE_V2, &vol_args) < 0) + return -errno; + + if (!(flags & BTRFS_SNAPSHOT_RECURSIVE)) + return 0; + + if (subvol_id == 0) { + r = btrfs_subvol_get_id_fd(old_fd, &subvol_id); + if (r < 0) + return r; + } + + args.key.min_offset = args.key.max_offset = subvol_id; + + while (btrfs_ioctl_search_args_compare(&args) <= 0) { + const struct btrfs_ioctl_search_header *sh; + unsigned i; + + args.key.nr_items = 256; + if (ioctl(old_fd, BTRFS_IOC_TREE_SEARCH, &args) < 0) + return -errno; + + if (args.key.nr_items <= 0) + break; + + FOREACH_BTRFS_IOCTL_SEARCH_HEADER(i, sh, args) { + _cleanup_free_ char *p = NULL, *c = NULL, *np = NULL; + struct btrfs_ioctl_ino_lookup_args ino_args; + const struct btrfs_root_ref *ref; + _cleanup_close_ int old_child_fd = -1, new_child_fd = -1; + + btrfs_ioctl_search_args_set(&args, sh); + + if (sh->type != BTRFS_ROOT_BACKREF_KEY) + continue; + if (sh->offset != subvol_id) + continue; + + ref = BTRFS_IOCTL_SEARCH_HEADER_BODY(sh); + + p = strndup((char*) ref + sizeof(struct btrfs_root_ref), le64toh(ref->name_len)); + if (!p) + return -ENOMEM; + + zero(ino_args); + ino_args.treeid = subvol_id; + ino_args.objectid = htole64(ref->dirid); + + if (ioctl(old_fd, BTRFS_IOC_INO_LOOKUP, &ino_args) < 0) + return -errno; + + /* The kernel returns an empty name if the + * subvolume is in the top-level directory, + * and otherwise appends a slash, so that we + * can just concatenate easily here, without + * adding a slash. */ + c = strappend(ino_args.name, p); + if (!c) + return -ENOMEM; + + old_child_fd = openat(old_fd, c, O_RDONLY|O_NOCTTY|O_CLOEXEC|O_DIRECTORY); + if (old_child_fd < 0) + return -errno; + + np = strjoin(subvolume, "/", ino_args.name, NULL); + if (!np) + return -ENOMEM; + + new_child_fd = openat(new_fd, np, O_RDONLY|O_NOCTTY|O_CLOEXEC|O_DIRECTORY); + if (new_child_fd < 0) + return -errno; + + /* When btrfs clones the subvolumes, child + * subvolumes appear as directories. Remove + * them, so that we can create a new snapshot + * in their place */ + if (unlinkat(new_child_fd, p, AT_REMOVEDIR) < 0) + return -errno; + + r = subvol_snapshot_children(old_child_fd, new_child_fd, p, sh->objectid, flags & ~BTRFS_SNAPSHOT_FALLBACK_COPY); + if (r < 0) + return r; + } + + /* Increase search key by one, to read the next item, if we can. */ + if (!btrfs_ioctl_search_args_inc(&args)) + break; + } + + return 0; +} + +int btrfs_subvol_snapshot_fd(int old_fd, const char *new_path, BtrfsSnapshotFlags flags) { + _cleanup_close_ int new_fd = -1; + const char *subvolume; + int r; + + assert(old_fd >= 0); + assert(new_path); + + r = btrfs_is_snapshot(old_fd); + if (r < 0) + return r; + if (r == 0) { + if (!(flags & BTRFS_SNAPSHOT_FALLBACK_COPY)) + return -EISDIR; + + r = btrfs_subvol_make(new_path); + if (r < 0) + return r; + + r = copy_directory_fd(old_fd, new_path, true); + if (r < 0) { + btrfs_subvol_remove(new_path, false); + return r; + } + + if (flags & BTRFS_SNAPSHOT_READ_ONLY) { + r = btrfs_subvol_set_read_only(new_path, true); + if (r < 0) { + btrfs_subvol_remove(new_path, false); + return r; + } + } + + return 0; + } + + r = extract_subvolume_name(new_path, &subvolume); + if (r < 0) + return r; + + new_fd = open_parent(new_path, O_RDONLY|O_NOCTTY|O_CLOEXEC|O_DIRECTORY); + if (new_fd < 0) + return new_fd; + + return subvol_snapshot_children(old_fd, new_fd, subvolume, 0, flags); +} + +int btrfs_subvol_snapshot(const char *old_path, const char *new_path, BtrfsSnapshotFlags flags) { + _cleanup_close_ int old_fd = -1; + + assert(old_path); + assert(new_path); + + old_fd = open(old_path, O_RDONLY|O_NOCTTY|O_CLOEXEC|O_DIRECTORY); + if (old_fd < 0) + return -errno; + + return btrfs_subvol_snapshot_fd(old_fd, new_path, flags); +} diff --git a/src/shared/btrfs-util.h b/src/shared/btrfs-util.h index e3ad98750..02e46e30e 100644 --- a/src/shared/btrfs-util.h +++ b/src/shared/btrfs-util.h @@ -46,6 +46,7 @@ typedef struct BtrfsQuotaInfo { typedef enum BtrfsSnapshotFlags { BTRFS_SNAPSHOT_FALLBACK_COPY = 1, BTRFS_SNAPSHOT_READ_ONLY = 2, + BTRFS_SNAPSHOT_RECURSIVE = 4, } BtrfsSnapshotFlags; int btrfs_is_snapshot(int fd); diff --git a/src/shared/machine-image.c b/src/shared/machine-image.c index ebe5a130f..0b41860b5 100644 --- a/src/shared/machine-image.c +++ b/src/shared/machine-image.c @@ -491,7 +491,7 @@ int image_clone(Image *i, const char *new_name, bool read_only) { case IMAGE_DIRECTORY: new_path = strjoina("/var/lib/machines/", new_name); - r = btrfs_subvol_snapshot(i->path, new_path, (read_only ? BTRFS_SNAPSHOT_READ_ONLY : 0) | BTRFS_SNAPSHOT_FALLBACK_COPY); + r = btrfs_subvol_snapshot(i->path, new_path, (read_only ? BTRFS_SNAPSHOT_READ_ONLY : 0) | BTRFS_SNAPSHOT_FALLBACK_COPY | BTRFS_SNAPSHOT_RECURSIVE); break; case IMAGE_RAW: -- 2.30.2