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Commit 0723a047 authored by Harald Hoyer's avatar Harald Hoyer Committed by Chris Mason
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btrfs: allow mounting btrfs subvolumes with different ro/rw options 



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: default avatarChris Mason <clm@fb.com>
parent 36523e95

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);