On Wed, Oct 28, 2015 at 07:25:10AM +0900, Neil Brown wrote: > > If you create a subvolume in btrfs and access it (by name) without > mounting it, then the subvolume looks like a separate mount to some > extent, returning a different st_dev to stat(), but it doesn't look like > a separate mount in that it isn't listed in /proc/mounts. This > inconsistency can confuse tools. > > This patch causes these subvolumes to become separate mounts by using > the VFS' automount functionality, much like NFS uses automount when it > discovered mountpoints on the server. > > The VFS currently makes it impossible to auto-mount a directory on to itself > (i.e. a bind mount). For NFS this isn't a problem as a new superblock > is created for the child filesystem so there are two separate dentries > (and inodes) for the one directory: one in the parent filesystem, one in > the child (note that the two superblocks share a common connection to > the server so there is still a lot of commonality). > > BTRFS has chosen instead to use a single superblock for all subvolumes. Naive question: was there a reason for that choice? --b. > This results in a single dentry for the subvol-root. A dentry which > must be auto-mounted on itself. -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
