On Tue, 20 May 2014 14:50:10 Astro Xe wrote: > On my box, the "used" value in the output of "btrfs filesystem df" is not > updated in a timely manner, after that one or more subvolumes have been > deleted. I need to execute "btrfs filesystem sync", in order to update the > value. > > How do I fix this? Or, could someone fix this in btrfs-progs, please? > > I suspect the cause is that subvolumes are marked immediately as deleted, > but cleaned up at a later time, is this right?
That appears to be the case. I've deleted subvolumes and then had btrfs take 10+ minutes to reclaim all the disk space. I've even had the system crash during the process (due to btrfs bugs that seem fixed in 3.14) and the space keeps getting freed after the reboot. Do we really want to make it the default to block on a btrfs sync? In the case of manual sysadmin tasks it's probably going to be preferable to run the delete command and then move on to other things. In the case of cron jobs we have to consider bulk performance, maybe it would be better for the authors of cron jobs to run a filesystem sync after deleting all snapshots to avoid driving the load average too high (I have had issues in the past when cron jobs to remove snapshots end up running at the same time as creating snapshots and scrubbing the filesystem). If a cron job was to delete dozens of snapshots and sync after each one would that cause more disk access than syncing once after all deletes? -- My Main Blog http://etbe.coker.com.au/ My Documents Blog http://doc.coker.com.au/ -- 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
