On Thu, Jan 30, 2020 at 1:02 PM Martin Steigerwald <martin@xxxxxxxxxxxx> wrote: > > Chris Murphy - 30.01.20, 17:37:42 CET: > > On Thu, Jan 30, 2020 at 3:41 AM Martin Steigerwald > <martin@xxxxxxxxxxxx> wrote: > > > Chris Murphy - 29.01.20, 23:55:06 CET: > > > > On Wed, Jan 29, 2020 at 2:20 PM Martin Steigerwald > > > > > > <martin@xxxxxxxxxxxx> wrote: > > > > > So if its just a cosmetic issue then I can wait for the patch to > > > > > land in linux-stable. Or does it still need testing? > > > > > > > > I'm not seeing it in linux-next. A reasonable short term work > > > > around > > > > is mount option 'metadata_ratio=1' and that's what needs more > > > > testing, because it seems decently likely mortal users will need > > > > an easy work around until a fix gets backported to stable. And > > > > that's gonna be a while, me thinks. > > > > > > > > Is that mount option sufficient? Or does it take a filtered > > > > balance? > > > > What's the most minimal balance needed? I'm hoping -dlimit=1 > > > > > > Does not make a difference. I did: > > > > > > - mount -o remount,metadata_ratio=1 /daten > > > - touch /daten/somefile > > > - dd if=/dev/zero of=/daten/someotherfile bs=1M count=500 > > > - sync > > > - df still reporting zero space free > > > > > > > I can't figure out a way to trigger this though, otherwise I'd be > > > > doing more testing. > > > > > > Sure. > > > > > > I am doing the balance -dlimit=1 thing next. With metadata_ratio=0 > > > again. > > > > > > % btrfs balance start -dlimit=1 /daten > > > Done, had to relocate 1 out of 312 chunks > > > > > > % LANG=en df -hT /daten > > > Filesystem Type Size Used Avail Use% Mounted on > > > /dev/mapper/sata-daten btrfs 400G 311G 0 100% /daten > > > > > > Okay, doing with metadata_ratio=1: > > > > > > % mount -o remount,metadata_ratio=1 /daten > > > > > > % btrfs balance start -dlimit=1 /daten > > > Done, had to relocate 1 out of 312 chunks > > > > > > % LANG=en df -hT /daten > > > Filesystem Type Size Used Avail Use% Mounted on > > > /dev/mapper/sata-daten btrfs 400G 311G 0 100% /daten > > > > > > > > > Okay, other suggestions? I'd like to avoid shuffling 311 GiB data > > > around using a full balance. > > > > There's earlier anecdotal evidence that -dlimit=10 will work. But you > > can just keep using -dlimit=1 and it'll balance a different block > > group each time (you can confirm/deny this with the block group > > address and extent count in dmesg for each balance). Count how many it > > takes to get df to stop misreporting. It may be a file system > > specific value. > > Lost the patience after 25 attempts: > > date; let I=I+1; echo "Balance $I"; btrfs balance start -dlimit=1 /daten > ; LANG=en df -hT /daten > Do 30. Jan 20:59:17 CET 2020 > Balance 25 > Done, had to relocate 1 out of 312 chunks > Filesystem Type Size Used Avail Use% Mounted on > /dev/mapper/sata-daten btrfs 400G 311G 0 100% /daten > > > Doing the -dlimit=10 balance now: > > % btrfs balance start -dlimit=10 /daten ; LANG=en df -hT /daten > Done, had to relocate 10 out of 312 chunks > Filesystem Type Size Used Avail Use% Mounted on > /dev/mapper/sata-daten btrfs 400G 311G 0 100% /daten > > Okay, enough of balancing for today. > > I bet I just wait for a proper fix, instead of needlessly shuffling data > around. What about unmounting and remounting? There is a proposed patch that David referenced in this thread, but it's looking like it papers over the real problem. But even if so, that'd get your file system working sooner than a proper fix, which I think (?) needs to be demonstrated to at least cause no new regressions in 5.6, before it'll be backported to stable. -- Chris Murphy
