Here's version 2 of providing the subvolume name and ID in /proc/mounts. It turns out that getting the name of a subvolume reliably is a bit trickier than it would seem because of how mounting subvolumes by ID is implemented. In particular, in that case, the dentry we get for the root of the mount is not necessarily attached to the dentry tree, which means that the obvious solution of just dumping the dentry does not work. The solution I put together makes the tradeoff of churning a bit more code in order to avoid implementing this with weird hacks.
Changes from v1 (https://lkml.org/lkml/2015/4/8/16): - Put subvol= last in show_options - Change commit log to remove comment about userspace having no way to know which subvolume is mounted, as David pointed out you can use btrfs inspect-internal rootid <mountpoint> - Split up patch 2 - Minor coding style fixes This still applies to v4.0-rc7. Tested manually and with the script below (updated from v1). Thanks! Omar Sandoval (6): Btrfs: lock superblock before remounting for rw subvol Btrfs: remove all subvol options before mounting top-level Btrfs: clean up error handling in mount_subvol() Btrfs: fail on mismatched subvol and subvolid mount options Btrfs: unify subvol= and subvolid= mounting Btrfs: show subvol= and subvolid= in /proc/mounts fs/btrfs/super.c | 376 ++++++++++++++++++++++++++++++++++++------------------- fs/seq_file.c | 1 + 2 files changed, 251 insertions(+), 126 deletions(-) Testing script: ---- #!/bin/sh set -e check_subvol () { NAME="$1" ID="$2" # Mount by name. mount -osubvol="$NAME" /dev/vdb /mnt if ! findmnt -fno OPTIONS /mnt | grep -F ",subvolid=$ID,subvol=$NAME"; then echo "Failed $NAME" >&2 umount /mnt exit 1 fi umount /mnt # Mount by ID. mount -osubvolid="$ID" /dev/vdb /mnt if ! findmnt -fno OPTIONS /mnt | grep -F ",subvolid=$ID,subvol=$NAME"; then echo "Failed $ID" >&2 umount /mnt exit 1 fi umount /mnt } check_default_subvol () { NAME="$1" ID="$2" mount /dev/vdb /mnt if ! findmnt -fno OPTIONS /mnt | grep -F ",subvolid=$ID,subvol=$NAME"; then echo "Failed default" >&2 umount /mnt exit 1 fi umount /mnt } mkfs.btrfs -f /dev/vdb mount /dev/vdb /mnt btrfs subvolume create /mnt/vol btrfs subvolume create /mnt/vol/nestedvol mkdir /mnt/dir btrfs subvolume create /mnt/dir/dirvol btrfs subvolume create /mnt/dir/dirvol/nesteddirvol mkdir /mnt/vol/voldir btrfs subvolume create /mnt/vol/voldir/voldirvol btrfs subvolume list /mnt umount /mnt check_subvol /vol 257 check_subvol /vol/nestedvol 258 check_subvol /dir/dirvol 259 check_subvol /dir/dirvol/nesteddirvol 260 check_subvol /vol/voldir/voldirvol 261 check_default_subvol / 5 mount /dev/vdb /mnt btrfs subvolume set-default 257 /mnt umount /mnt check_default_subvol /vol 257 if mount -osubvolid=258,subvol=/vol /dev/vdb /mnt 2>/dev/null; then umount /mnt echo "Mount of mismatched subvol and subvolid should have failed" >&2 exit 1 fi ---- -- 2.3.5 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
