From 0723a0473fb48a1c93b113a28665b64ce5faf35a Mon Sep 17 00:00:00 2001 From: Harald Hoyer Date: Tue, 19 Nov 2013 11:36:05 +0100 Subject: [PATCH] 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: Chris Mason --- fs/btrfs/super.c | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c index d4878ddba87a..994c40955315 100644 --- a/fs/btrfs/super.c +++ b/fs/btrfs/super.c @@ -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); -- 2.34.1