* requested by subvol=/path. That way the callchain is straightforward and we
* don't have to play tricks with the mount options and recursive calls to
* btrfs_mount.
+ *
+ * The new btrfs_root_fs_type also servers as a tag for the bdev_holder.
*/
static struct file_system_type btrfs_fs_type;
static struct file_system_type btrfs_root_fs_type;
static struct dentry *mount_subvol(const char *subvol_name, u64 subvol_objectid,
int flags, const char *device_name,
- char *data)
+ char *data, struct vfsmount *mnt)
{
struct dentry *root;
- struct vfsmount *mnt = NULL;
- char *newargs;
int ret;
- newargs = setup_root_args(data);
- if (!newargs) {
- root = ERR_PTR(-ENOMEM);
- goto out;
- }
-
- mnt = vfs_kern_mount(&btrfs_fs_type, flags, device_name, newargs);
- if (PTR_ERR_OR_ZERO(mnt) == -EBUSY) {
- if (flags & SB_RDONLY) {
- mnt = vfs_kern_mount(&btrfs_fs_type, flags & ~SB_RDONLY,
- device_name, newargs);
- } else {
- mnt = vfs_kern_mount(&btrfs_fs_type, flags | SB_RDONLY,
- device_name, newargs);
- if (IS_ERR(mnt)) {
- root = ERR_CAST(mnt);
- mnt = NULL;
- goto out;
- }
-
- down_write(&mnt->mnt_sb->s_umount);
- ret = btrfs_remount(mnt->mnt_sb, &flags, NULL);
- up_write(&mnt->mnt_sb->s_umount);
- if (ret < 0) {
- root = ERR_PTR(ret);
- goto out;
- }
- }
- }
- if (IS_ERR(mnt)) {
- root = ERR_CAST(mnt);
- mnt = NULL;
- goto out;
- }
-
if (!subvol_name) {
if (!subvol_objectid) {
ret = get_default_subvol_objectid(btrfs_sb(mnt->mnt_sb),
out:
mntput(mnt);
- kfree(newargs);
kfree(subvol_name);
return root;
}
return ret;
}
+/*
+ * Find a superblock for the given device / mount point.
+ *
+ * Note: This is based on mount_bdev from fs/super.c with a few additions
+ * for multiple device setup. Make sure to keep it in sync.
+ */
static struct dentry *btrfs_mount_root(struct file_system_type *fs_type,
int flags, const char *device_name, void *data)
{
security_free_mnt_opts(&new_sec_opts);
return ERR_PTR(error);
}
+
/*
- * Find a superblock for the given device / mount point.
+ * Mount function which is called by VFS layer.
*
- * Note: This is based on get_sb_bdev from fs/super.c with a few additions
- * for multiple device setup. Make sure to keep it in sync.
+ * In order to allow mounting a subvolume directly, btrfs uses mount_subtree()
+ * which needs vfsmount* of device's root (/). This means device's root has to
+ * be mounted internally in any case.
+ *
+ * Operation flow:
+ * 1. Parse subvol id related options for later use in mount_subvol().
+ *
+ * 2. Mount device's root (/) by calling vfs_kern_mount().
+ *
+ * NOTE: vfs_kern_mount() is used by VFS to call btrfs_mount() in the
+ * first place. In order to avoid calling btrfs_mount() again, we use
+ * different file_system_type which is not registered to VFS by
+ * register_filesystem() (btrfs_root_fs_type). As a result,
+ * btrfs_mount_root() is called. The return value will be used by
+ * mount_subtree() in mount_subvol().
+ *
+ * 3. Call mount_subvol() to get the dentry of subvolume. Since there is
+ * "btrfs subvolume set-default", mount_subvol() is called always.
*/
static struct dentry *btrfs_mount(struct file_system_type *fs_type, int flags,
const char *device_name, void *data)
{
- struct block_device *bdev = NULL;
- struct super_block *s;
struct btrfs_fs_devices *fs_devices = NULL;
- struct btrfs_fs_info *fs_info = NULL;
- struct security_mnt_opts new_sec_opts;
+ struct vfsmount *mnt_root;
+ struct dentry *root;
fmode_t mode = FMODE_READ;
char *subvol_name = NULL;
u64 subvol_objectid = 0;
return ERR_PTR(error);
}
- if (subvol_name || subvol_objectid != BTRFS_FS_TREE_OBJECTID) {
- /* mount_subvol() will free subvol_name. */
- return mount_subvol(subvol_name, subvol_objectid, flags,
- device_name, data);
- }
-
- security_init_mnt_opts(&new_sec_opts);
- if (data) {
- error = parse_security_options(data, &new_sec_opts);
- if (error)
- return ERR_PTR(error);
- }
-
- error = btrfs_scan_one_device(device_name, mode, fs_type, &fs_devices);
- if (error)
- goto error_sec_opts;
-
- /*
- * Setup a dummy root and fs_info for test/set super. This is because
- * we don't actually fill this stuff out until open_ctree, but we need
- * it for searching for existing supers, so this lets us do that and
- * then open_ctree will properly initialize everything later.
- */
- fs_info = kzalloc(sizeof(struct btrfs_fs_info), GFP_KERNEL);
- if (!fs_info) {
- error = -ENOMEM;
- goto error_sec_opts;
- }
-
- fs_info->fs_devices = fs_devices;
-
- fs_info->super_copy = kzalloc(BTRFS_SUPER_INFO_SIZE, GFP_KERNEL);
- fs_info->super_for_commit = kzalloc(BTRFS_SUPER_INFO_SIZE, GFP_KERNEL);
- security_init_mnt_opts(&fs_info->security_opts);
- if (!fs_info->super_copy || !fs_info->super_for_commit) {
- error = -ENOMEM;
- goto error_fs_info;
- }
-
- error = btrfs_open_devices(fs_devices, mode, fs_type);
- if (error)
- goto error_fs_info;
-
- if (!(flags & SB_RDONLY) && fs_devices->rw_devices == 0) {
- error = -EACCES;
- goto error_close_devices;
- }
-
- bdev = fs_devices->latest_bdev;
- s = sget(fs_type, btrfs_test_super, btrfs_set_super, flags | SB_NOSEC,
- fs_info);
- if (IS_ERR(s)) {
- error = PTR_ERR(s);
- goto error_close_devices;
- }
+ /* mount device's root (/) */
+ mnt_root = vfs_kern_mount(&btrfs_root_fs_type, flags, device_name, data);
+ if (PTR_ERR_OR_ZERO(mnt_root) == -EBUSY) {
+ if (flags & SB_RDONLY) {
+ mnt_root = vfs_kern_mount(&btrfs_root_fs_type,
+ flags & ~SB_RDONLY, device_name, data);
+ } else {
+ mnt_root = vfs_kern_mount(&btrfs_root_fs_type,
+ flags | SB_RDONLY, device_name, data);
+ if (IS_ERR(mnt_root)) {
+ root = ERR_CAST(mnt_root);
+ goto out;
+ }
- if (s->s_root) {
- btrfs_close_devices(fs_devices);
- free_fs_info(fs_info);
- if ((flags ^ s->s_flags) & SB_RDONLY)
- error = -EBUSY;
- } else {
- snprintf(s->s_id, sizeof(s->s_id), "%pg", bdev);
- btrfs_sb(s)->bdev_holder = fs_type;
- error = btrfs_fill_super(s, fs_devices, data);
- }
- if (error) {
- deactivate_locked_super(s);
- goto error_sec_opts;
+ down_write(&mnt_root->mnt_sb->s_umount);
+ error = btrfs_remount(mnt_root->mnt_sb, &flags, NULL);
+ up_write(&mnt_root->mnt_sb->s_umount);
+ if (error < 0) {
+ root = ERR_PTR(error);
+ mntput(mnt_root);
+ goto out;
+ }
+ }
}
-
- fs_info = btrfs_sb(s);
- error = setup_security_options(fs_info, s, &new_sec_opts);
- if (error) {
- deactivate_locked_super(s);
- goto error_sec_opts;
+ if (IS_ERR(mnt_root)) {
+ root = ERR_CAST(mnt_root);
+ goto out;
}
- return dget(s->s_root);
+ /* mount_subvol() will free subvol_name and mnt_root */
+ root = mount_subvol(subvol_name, subvol_objectid, flags, device_name,
+ data, mnt_root);
-error_close_devices:
- btrfs_close_devices(fs_devices);
-error_fs_info:
- free_fs_info(fs_info);
-error_sec_opts:
- security_free_mnt_opts(&new_sec_opts);
- return ERR_PTR(error);
+out:
+ return root;
}
static void btrfs_resize_thread_pool(struct btrfs_fs_info *fs_info,
switch (cmd) {
case BTRFS_IOC_SCAN_DEV:
ret = btrfs_scan_one_device(vol->name, FMODE_READ,
- &btrfs_fs_type, &fs_devices);
+ &btrfs_root_fs_type, &fs_devices);
break;
case BTRFS_IOC_DEVICES_READY:
ret = btrfs_scan_one_device(vol->name, FMODE_READ,
- &btrfs_fs_type, &fs_devices);
+ &btrfs_root_fs_type, &fs_devices);
if (ret)
break;
ret = !(fs_devices->num_devices == fs_devices->total_devices);
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