On Mon, Sep 25, 2017 at 04:27:07PM +0900, Misono, Tomohiro wrote:
> Add mount_root() and new file_system_type for preparation of cleanup of
> btrfs_mount(). Code path is not changed yet.
>
> mount_root() is almost the same as current btrfs_mount(), but doesn't
> have subvolume related part.
>
> Signed-off-by: Tomohiro Misono <misono.tomohiro@xxxxxxxxxxxxxx>
> ---
> fs/btrfs/super.c | 116 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 116 insertions(+)
>
> diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
> index 12540b6..fe43606 100644
> --- a/fs/btrfs/super.c
> +++ b/fs/btrfs/super.c
> @@ -66,6 +66,7 @@
>
> static const struct super_operations btrfs_super_ops;
> static struct file_system_type btrfs_fs_type;
> +static struct file_system_type btrfs_root_fs_type;
A comment why we need this would be useful.
>
> static int btrfs_remount(struct super_block *sb, int *flags, char *data);
>
> @@ -1514,6 +1515,112 @@ static int setup_security_options(struct btrfs_fs_info *fs_info,
> return ret;
> }
>
> +static struct dentry *mount_root(struct file_system_type *fs_type, int flags,
'mount_root' is too generic and could be confused with other mount_*
functions from VFS, btrfs_mount_root would be better.
> + 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;
> + fmode_t mode = FMODE_READ;
> + char *subvol_name = NULL;
> + u64 subvol_objectid = 0;
> + int error = 0;
> +
> + if (!(flags & MS_RDONLY))
> + mode |= FMODE_WRITE;
> +
> + error = btrfs_parse_early_options(data, mode, fs_type,
> + &subvol_name, &subvol_objectid,
> + &fs_devices);
> + if (error) {
> + kfree(subvol_name);
> + return ERR_PTR(error);
> + }
> +
> + 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_NOFS);
Why GFP_NOFS?
> + 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_NOFS);
> + fs_info->super_for_commit = kzalloc(BTRFS_SUPER_INFO_SIZE, GFP_NOFS);
Also here. Current code uses GFP_KERNEL so this might got switched in
the meantim.
> + 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 & MS_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 | MS_NOSEC,
> + fs_info);
> + if (IS_ERR(s)) {
> + error = PTR_ERR(s);
> + goto error_close_devices;
> + }
> +
> + if (s->s_root) {
> + btrfs_close_devices(fs_devices);
> + free_fs_info(fs_info);
> + if ((flags ^ s->s_flags) & MS_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;
> + }
> +
> + 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;
> + }
> +
> + return dget(s->s_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);
> +}
> /*
> * Find a superblock for the given device / mount point.
> *
> @@ -2133,6 +2240,15 @@ static struct file_system_type btrfs_fs_type = {
> .kill_sb = btrfs_kill_super,
> .fs_flags = FS_REQUIRES_DEV | FS_BINARY_MOUNTDATA,
> };
> +
> +static struct file_system_type btrfs_root_fs_type = {
> + .owner = THIS_MODULE,
> + .name = "btrfs",
> + .mount = mount_root,
> + .kill_sb = btrfs_kill_super,
> + .fs_flags = FS_REQUIRES_DEV | FS_BINARY_MOUNTDATA,
> +};
> +
> MODULE_ALIAS_FS("btrfs");
>
> static int btrfs_control_open(struct inode *inode, struct file *file)
> --
> 2.9.5
>
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