On Tue, Feb 19, 2013 at 02:22:27PM -0600, Mitch Harder wrote: > I've encountered an issue where the space from previously deleted > snapshots is not being freed up by the cleaner thread. > > I'm only encountering this issue when I mount with the inode_cache option. > > I've reproduced this on a 3.7.9 kernel merged with the latest > for-linus branch. No additional patches are involved. My testing > partition is 16 GB. > > There is nothing in dmesg indicating any issues. > > A simple manual test can reproduce the issue on my box > > (1) Format a fresh, scratch btrfs partition (it would probably work > with an existing test partition, but I always like to test things that > seem broken on a scratch partition). > (2) Mount partition (my options are -o > compress-force=lzo,inode_cache). My mount command was: > mount -o compress-force=lzo,inode_cache /dev/sda7 /mnt/benchmark/ > (3) Make a subvolume: cd /mnt/<device>; btrfs su create test1 > (4) Untar kernel sources to the subvolume: cd test1; tar -xpf > <path/to/kernel/source/tarball> > I believe anything you use to populate the subvolume is sufficient. > (5) Make a note of the disk usage: df -T /mnt/<device> > (6) Remove the subvolume: cd ..; btrfs su delete test1 > (7) Wait 2 minutes, and notice that the space has not been freed up. > I've waited much longer, but I forget the exact timeout on the cleaner > thread. > df -T /mnt/<device> > > If I unmount and remount the partition with the same mount options, > the cleaner will begin to correctly free the space.
Hi Mitch, Good summary. > > I've never used the inode_cache option before, so I'll try a few other > kernels to see if this is a regression. I think I know why inode_cache keeps us from freeing space, inode_cache adds a cache_inode in each btrfs root, and this cache_inode will be iput at the very last of stage during umount, ie. after we do cleanup work on old snapshot/subvols, where we free the space. A remount will force btrfs to do cleanup work on old snapshots during mount. This may explain the situation. thanks, liubo > -- > To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in > the body of a message to majord...@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
