shared: add new btrfs-util.[ch] helpers for doing common btrfs operation

1 files changed, 294 insertions, 0 deletions

diff --git a/src/shared/btrfs-util.c b/src/shared/btrfs-util.c
new file mode 100644
index 0000000000..fcf543a465
--- /dev/null
+++ b/src/shared/btrfs-util.c
@@ -0,0 +1,294 @@
+/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
+
+/***
+  This file is part of systemd.
+
+  Copyright 2014 Lennart Poettering
+
+  systemd is free software; you can redistribute it and/or modify it
+  under the terms of the GNU Lesser General Public License as published by
+  the Free Software Foundation; either version 2.1 of the License, or
+  (at your option) any later version.
+
+  systemd is distributed in the hope that it will be useful, but
+  WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+  Lesser General Public License for more details.
+
+  You should have received a copy of the GNU Lesser General Public License
+  along with systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+#include <stdlib.h>
+#include <sys/vfs.h>
+#include <sys/stat.h>
+
+#ifdef HAVE_LINUX_BTRFS_H
+#include <linux/btrfs.h>
+#endif
+
+#include "missing.h"
+#include "util.h"
+#include "path-util.h"
+#include "macro.h"
+#include "strv.h"
+#include "copy.h"
+#include "btrfs-util.h"
+
+static int validate_subvolume_name(const char *name) {
+
+        if (!filename_is_valid(name))
+                return -EINVAL;
+
+        if (strlen(name) > BTRFS_SUBVOL_NAME_MAX)
+                return -E2BIG;
+
+        return 0;
+}
+
+static int open_parent(const char *path, int flags) {
+        _cleanup_free_ char *parent = NULL;
+        int r, fd;
+
+        assert(path);
+
+        r = path_get_parent(path, &parent);
+        if (r < 0)
+                return r;
+
+        fd = open(parent, flags);
+        if (fd < 0)
+                return -errno;
+
+        return fd;
+}
+
+static int extract_subvolume_name(const char *path, const char **subvolume) {
+        const char *fn;
+        int r;
+
+        assert(path);
+        assert(subvolume);
+
+        fn = basename(path);
+
+        r = validate_subvolume_name(fn);
+        if (r < 0)
+                return r;
+
+        *subvolume = fn;
+        return 0;
+}
+
+int btrfs_is_snapshot(int fd) {
+        struct stat st;
+        struct statfs sfs;
+
+        if (fstatfs(fd, &sfs) < 0)
+                return -errno;
+
+        if (!F_TYPE_EQUAL(sfs.f_type, BTRFS_SUPER_MAGIC))
+                return 0;
+
+        if (fstat(fd, &st) < 0)
+                return -errno;
+
+        /* On btrfs subvolumes always have the inode 256 */
+
+        return S_ISDIR(st.st_mode) && st.st_ino == 256;
+}
+
+int btrfs_subvol_snapshot(const char *old_path, const char *new_path, bool read_only, bool fallback_copy) {
+        struct btrfs_ioctl_vol_args_v2 args = {
+                .flags = read_only ? BTRFS_SUBVOL_RDONLY : 0,
+        };
+        _cleanup_close_ int old_fd = -1, new_fd = -1;
+        const char *subvolume;
+        int r;
+
+        assert(old_path);
+
+        old_fd = open(old_path, O_RDONLY|O_NOCTTY|O_CLOEXEC|O_DIRECTORY);
+        if (old_fd < 0)
+                return -errno;
+
+        r = btrfs_is_snapshot(old_fd);
+        if (r < 0)
+                return r;
+        if (r == 0) {
+
+                if (fallback_copy) {
+                        r = btrfs_subvol_make(new_path);
+                        if (r < 0)
+                                return r;
+
+                        r = copy_tree_fd(old_fd, new_path, true);
+                        if (r < 0) {
+                                btrfs_subvol_remove(new_path);
+                                return r;
+                        }
+
+                        if (read_only) {
+                                r = btrfs_subvol_read_only(new_path, true);
+                                if (r < 0) {
+                                        btrfs_subvol_remove(new_path);
+                                        return r;
+                                }
+                        }
+
+                        return 0;
+                }
+
+                return -EISDIR;
+        }
+
+        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_make(const char *path) {
+        struct btrfs_ioctl_vol_args args = {};
+        _cleanup_close_ int fd = -1;
+        const char *subvolume;
+        int r;
+
+        assert(path);
+
+        r = extract_subvolume_name(path, &subvolume);
+        if (r < 0)
+                return r;
+
+        fd = open_parent(path, O_RDONLY|O_NOCTTY|O_CLOEXEC|O_DIRECTORY);
+        if (fd < 0)
+                return fd;
+
+        strncpy(args.name, subvolume, sizeof(args.name)-1);
+
+        if (ioctl(fd, BTRFS_IOC_SUBVOL_CREATE, &args) < 0)
+                return -errno;
+
+        return 0;
+}
+
+int btrfs_subvol_remove(const char *path) {
+        struct btrfs_ioctl_vol_args args = {};
+        _cleanup_close_ int fd = -1;
+        const char *subvolume;
+        int r;
+
+        assert(path);
+
+        r = extract_subvolume_name(path, &subvolume);
+        if (r < 0)
+                return r;
+
+        fd = open_parent(path, O_RDONLY|O_NOCTTY|O_CLOEXEC|O_DIRECTORY);
+        if (fd < 0)
+                return fd;
+
+        strncpy(args.name, subvolume, sizeof(args.name)-1);
+
+        if (ioctl(fd, BTRFS_IOC_SNAP_DESTROY, &args) < 0)
+                return -errno;
+
+        return 0;
+}
+
+int btrfs_subvol_read_only(const char *path, bool b) {
+        _cleanup_close_ int fd = -1;
+        uint64_t flags, nflags;
+
+        fd = open(path, O_RDONLY|O_NOCTTY|O_CLOEXEC);
+        if (fd < 0)
+                return -errno;
+
+        if (ioctl(fd, BTRFS_IOC_SUBVOL_GETFLAGS, &flags) < 0)
+                return -errno;
+
+        if (b)
+                nflags = flags | BTRFS_SUBVOL_RDONLY;
+        else
+                nflags = flags & ~BTRFS_SUBVOL_RDONLY;
+
+        if (flags == nflags)
+                return 0;
+
+        if (ioctl(fd, BTRFS_IOC_SUBVOL_SETFLAGS, &nflags) < 0)
+                return -errno;
+
+        return 0;
+}
+
+int btrfs_reflink(int infd, int outfd) {
+        int r;
+
+        assert(infd >= 0);
+        assert(outfd >= 0);
+
+        r = ioctl(outfd, BTRFS_IOC_CLONE, infd);
+        if (r < 0)
+                return -errno;
+
+        return 0;
+}
+
+int btrfs_get_block_device(const char *path, dev_t *dev) {
+        struct btrfs_ioctl_fs_info_args fsi = {};
+        _cleanup_close_ int fd = -1;
+        uint64_t id;
+
+        assert(path);
+        assert(dev);
+
+        fd = open(path, O_RDONLY|O_NOCTTY|O_CLOEXEC|O_DIRECTORY);
+        if (fd < 0)
+                return -errno;
+
+        if (ioctl(fd, BTRFS_IOC_FS_INFO, &fsi) < 0)
+                return -errno;
+
+        /* We won't do this for btrfs RAID */
+        if (fsi.num_devices != 1)
+                return 0;
+
+        for (id = 1; id <= fsi.max_id; id++) {
+                struct btrfs_ioctl_dev_info_args di = {
+                        .devid = id,
+                };
+                struct stat st;
+
+                if (ioctl(fd, BTRFS_IOC_DEV_INFO, &di) < 0) {
+                        if (errno == ENODEV)
+                                continue;
+
+                        return -errno;
+                }
+
+                if (stat((char*) di.path, &st) < 0)
+                        return -errno;
+
+                if (!S_ISBLK(st.st_mode))
+                        return -ENODEV;
+
+                if (major(st.st_rdev) == 0)
+                        return -ENODEV;
+
+                *dev = st.st_rdev;
+                return 1;
+        }
+
+        return -ENODEV;
+}