btrfs: allow mounting btrfs subvolumes with different ro/rw options (0723a047) · Commits · 戴 / test

Given the following /etc/fstab entries: /dev/sda3 /mnt/foo btrfs subvol=foo,ro 0 0 /dev/sda3 /mnt/bar btrfs subvol=bar,rw 0 0 you can't issue: $ mount /mnt/foo $ mount /mnt/bar You would have to do: $ mount /mnt/foo $ mount -o remount,rw /mnt/foo $ mount --bind -o remount,ro /mnt/foo $ mount /mnt/bar or $ mount /mnt/bar $ mount --rw /mnt/foo $ mount --bind -o remount,ro /mnt/foo With this patch you can do $ mount /mnt/foo $ mount /mnt/bar $ cat /proc/self/mountinfo 49 33 0:41 /foo /mnt/foo ro,relatime shared:36 - btrfs /dev/sda3 rw,ssd,space_cache 87 33 0:41 /bar /mnt/bar rw,relatime shared:74 - btrfs /dev/sda3 rw,ssd,space_cache Signed-off-by:

Chris Mason <clm@fb.com>

fs/btrfs/super.c

+22 −0

Original line number	Diff line number	Diff line
		@@ -66,6 +66,8 @@
		static const struct super_operations btrfs_super_ops;
		static struct file_system_type btrfs_fs_type;

		static int btrfs_remount(struct super_block sb, int flags, char *data);

		static const char *btrfs_decode_error(int errno)
		{
		char *errstr = "unknown";
		@@ -1185,6 +1187,26 @@ static struct dentry mount_subvol(const char subvol_name, int flags,
		mnt = vfs_kern_mount(&btrfs_fs_type, flags, device_name,
		newargs);
		kfree(newargs);

		if (PTR_RET(mnt) == -EBUSY) {
		if (flags & MS_RDONLY) {
		mnt = vfs_kern_mount(&btrfs_fs_type, flags & ~MS_RDONLY, device_name,
		newargs);
		} else {
		int r;
		mnt = vfs_kern_mount(&btrfs_fs_type, flags \| MS_RDONLY, device_name,
		newargs);
		if (IS_ERR(mnt))
		return ERR_CAST(mnt);

		r = btrfs_remount(mnt->mnt_sb, &flags, NULL);
		if (r < 0) {
		/* FIXME: release vfsmount mnt ??*/
		return ERR_PTR(r);
		}
		}
		}

		if (IS_ERR(mnt))
		return ERR_CAST(mnt);

Admin message