Messages in this thread | | | Date | Mon, 11 May 2015 18:07:38 +0200 | From | David Sterba <> | Subject | Re: [PATCH v2 1/6] Btrfs: lock superblock before remounting for rw subvol |
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On Thu, Apr 09, 2015 at 02:34:51PM -0700, Omar Sandoval wrote: > Since commit 0723a0473fb4 ("btrfs: allow mounting btrfs subvolumes with > different ro/rw options"), when mounting a subvolume read/write when > another subvolume has previously been mounted read-only, we first do a > remount. However, this should be done with the superblock locked, as per > sync_filesystem(): > > /* > * We need to be protected against the filesystem going from > * r/o to r/w or vice versa. > */ > WARN_ON(!rwsem_is_locked(&sb->s_umount)); > > This WARN_ON can easily be hit with: > > mkfs.btrfs -f /dev/vdb > mount /dev/vdb /mnt > btrfs subvol create /mnt/vol1 > btrfs subvol create /mnt/vol2 > umount /mnt > mount -oro,subvol=/vol1 /dev/vdb /mnt > mount -orw,subvol=/vol2 /dev/vdb /mnt2 > > Fixes: 0723a0473fb4 ("btrfs: allow mounting btrfs subvolumes with different ro/rw options") > Signed-off-by: Omar Sandoval <osandov@osandov.com>
Reviewed-by: David Sterba <dsterba@suse.cz>
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