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

.gitignore

@@ -134,6 +134,7 @@
 /test-async
 /test-barrier
 /test-boot-timestamp
+/test-btrfs
 /test-bus-chat
 /test-bus-cleanup
 /test-bus-creds

Makefile.am

@@ -891,7 +891,9 @@ libsystemd_shared_la_SOURCES = \
 	src/shared/memfd-util.h \
 	src/shared/uid-range.c \
 	src/shared/uid-range.h \
-	src/shared/nss-util.h
+	src/shared/nss-util.h \
+	src/shared/btrfs-util.c \
+	src/shared/btrfs-util.h
 
 if HAVE_UTMP
 libsystemd_shared_la_SOURCES += \
@@ -1319,7 +1321,8 @@ manual_tests += \
 	test-install \
 	test-watchdog \
 	test-log \
-	test-ipcrm
+	test-ipcrm \
+	test-btrfs
 
 if HAVE_KMOD
 manual_tests += \
@@ -1756,6 +1759,12 @@ test_ipcrm_LDADD = \
 	libsystemd-shared.la \
 	-lrt
 
+test_btrfs_SOURCES = \
+	src/test/test-btrfs.c
+
+test_btrfs_LDADD = \
+	libsystemd-shared.la
+
 test_rtnl_manual_SOURCES = \
 	src/test/test-rtnl-manual.c
 

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;
+}

src/shared/btrfs-util.h

@@ -0,0 +1,34 @@
+/*-*- 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 <stdbool.h>
+#include <sys/types.h>
+
+int btrfs_is_snapshot(int fd);
+
+int btrfs_subvol_make(const char *path);
+int btrfs_subvol_remove(const char *path);
+int btrfs_subvol_snapshot(const char *old_path, const char *new_path, bool read_only, bool fallback_copy);
+int btrfs_subvol_read_only(const char *path, bool b);
+
+int btrfs_reflink(int infd, int outfd);
+
+int btrfs_get_block_device(const char *path, dev_t *dev);

src/shared/copy.c

@@ -22,6 +22,7 @@
 #include <sys/sendfile.h>
 
 #include "util.h"
+#include "btrfs-util.h"
 #include "copy.h"
 
 int copy_bytes(int fdf, int fdt, off_t max_bytes) {
@@ -187,20 +188,28 @@ static int fd_copy_node(int df, const char *from, const struct stat *st, int dt,
         return r;
 }
 
-static int fd_copy_directory(int df, const char *from, const struct stat *st, int dt, const char *to, dev_t original_device, bool merge) {
+static int fd_copy_directory(
+                int df,
+                const char *from,
+                const struct stat *st,
+                int dt,
+                const char *to,
+                dev_t original_device,
+                bool merge) {
+
         _cleanup_close_ int fdf = -1, fdt = -1;
         _cleanup_closedir_ DIR *d = NULL;
         struct dirent *de;
         bool created;
         int r;
 
-        assert(from);
         assert(st);
         assert(to);
 
+        if (from)
                 fdf = openat(df, from, O_RDONLY|O_DIRECTORY|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW);
-        if (fdf < 0)
+        else
-                return -errno;
+                fdf = fcntl(df, F_DUPFD_CLOEXEC, 3);
 
         d = fdopendir(fdf);
         if (!d)
@@ -287,6 +296,22 @@ int copy_tree(const char *from, const char *to, bool merge) {
                 return -ENOTSUP;
 }
 
+int copy_tree_fd(int dirfd, const char *to, bool merge) {
+
+        struct stat st;
+
+        assert(dirfd >= 0);
+        assert(to);
+
+        if (fstat(dirfd, &st) < 0)
+                return -errno;
+
+        if (!S_ISDIR(st.st_mode))
+                return -ENOTDIR;
+
+        return fd_copy_directory(dirfd, NULL, &st, AT_FDCWD, to, st.st_dev, merge);
+}
+
 int copy_file_fd(const char *from, int fdt) {
         _cleanup_close_ int fdf = -1;
 

src/shared/copy.h

@@ -27,4 +27,5 @@
 int copy_file_fd(const char *from, int to);
 int copy_file(const char *from, const char *to, int flags, mode_t mode);
 int copy_tree(const char *from, const char *to, bool merge);
+int copy_tree_fd(int dirfd, const char *to, bool merge);
 int copy_bytes(int fdf, int fdt, off_t max_bytes);

src/test/test-btrfs.c

@@ -0,0 +1,68 @@
+/*-*- 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 "log.h"
+#include "btrfs-util.h"
+#include "fileio.h"
+
+int main(int argc, char *argv[]) {
+        int r;
+
+        r = btrfs_subvol_make("/xxxtest");
+        if (r < 0)
+                log_error_errno(r, "Failed to make subvolume: %m");
+
+        r = write_string_file("/xxxtest/afile", "ljsadhfljasdkfhlkjdsfha");
+        if (r < 0)
+                log_error_errno(r, "Failed to write file: %m");
+
+        r = btrfs_subvol_snapshot("/xxxtest", "/xxxtest2", false, false);
+        if (r < 0)
+                log_error_errno(r, "Failed to make snapshot: %m");
+
+        r = btrfs_subvol_snapshot("/xxxtest", "/xxxtest3", true, false);
+        if (r < 0)
+                log_error_errno(r, "Failed to make snapshot: %m");
+
+        r = btrfs_subvol_remove("/xxxtest");
+        if (r < 0)
+                log_error_errno(r, "Failed to remove subvolume: %m");
+
+        r = btrfs_subvol_remove("/xxxtest2");
+        if (r < 0)
+                log_error_errno(r, "Failed to remove subvolume: %m");
+
+        r = btrfs_subvol_remove("/xxxtest3");
+        if (r < 0)
+                log_error_errno(r, "Failed to remove subvolume: %m");
+
+        r = btrfs_subvol_snapshot("/etc", "/etc2", true, true);
+        if (r < 0)
+                log_error_errno(r, "Failed to make snapshot: %m");
+
+        r = btrfs_subvol_remove("/etc2");
+        if (r < 0)
+                log_error_errno(r, "Failed to remove subvolume: %m");
+
+        return 0;
+}