On Tue, 10 Nov 2015 16:16:26 +0800 Qu Wenruo <quwenruo.bt...@gmx.com> wrote:
> So if things are correct, the btrfs you converted should still be in > mixed-bg mode. > A recent 'btrfs fi df' command should show things like: > Data+Metadata, DUP: total=512.00MiB, used=68.23MiB Actually not quite. After all the rebalancing, I currently have: Data, single: total=8.37TiB, used=7.50TiB System, DUP: total=32.00MiB, used=592.00KiB Metadata, DUP: total=8.00GiB, used=6.42GiB GlobalReserve, single: total=512.00MiB, used=0.00B > > But as we know recently there were reports that it now causes corruption or > > does not work. So I wonder what happened that broke it, and is there really > > no > > simpler fix? Even if requiring the user to balance to get rid of the bloated > > Metadata like I had to. > > > > Yes, current btrfs-convert has problem on marking chunk meta or data. > Resulting some data extents may lay in metadata chunk, and vice verse. > At least it won't pass latest btrfsck. > > In that incorrect chunk layout, I'm not surprised any thing go wrong. Made an experiment: # dd if=/dev/zero bs=1M count=1 seek=100000 of=100G 1+0 records in 1+0 records out 1048576 bytes (1.0 MB) copied, 0.0023896 s, 439 MB/s # losetup /dev/loop7 100G # mkfs.ext4 /dev/loop7 // Success # mount /dev/loop7 /mnt/tmp1/ // Copy some files there # df -h /mnt/tmp1/ Filesystem Size Used Avail Use% Mounted on /dev/loop7 96G 2.6G 89G 3% /mnt/tmp1 # umount /mnt/tmp1/ # btrfs-convert -d /dev/loop7 creating btrfs metadata. creating ext2fs image file. cleaning up system chunk. conversion complete. # mount /dev/loop7 /mnt/tmp1/ # btrfs fi df /mnt/tmp1/ Data, single: total=65.00GiB, used=1.32GiB System, single: total=32.00MiB, used=12.00KiB Metadata, single: total=32.63GiB, used=2.91GiB GlobalReserve, single: total=92.00MiB, used=0.00B # btrfs sub del /mnt/tmp1/ext2_saved Transaction commit: none (default) Delete subvolume '/mnt/tmp1/ext2_saved' # btrfs fi df /mnt/tmp1/ Data, single: total=10.00GiB, used=120.12MiB System, single: total=32.00MiB, used=4.00KiB Metadata, single: total=4.00GiB, used=2.37GiB GlobalReserve, single: total=52.00MiB, used=0.00B // It has 2.6 GB of files, and most of them are now accounted as "Metadata". # btrfs fi balance start -m /mnt/tmp1/ Done, had to relocate 5 out of 7 chunks // They are now reclassified as data: # btrfs fi df /mnt/tmp1/ Data, single: total=10.00GiB, used=2.49GiB System, single: total=32.00MiB, used=4.00KiB Metadata, single: total=1.00GiB, used=468.00KiB GlobalReserve, single: total=4.00MiB, used=0.00B // Unmount, mount, checked all files integrity with 'cfv', all files are present and there is no corruption. So this behaves just like I remember it to, after conversion at first a large part of the data will show up as Metadata, but a balance fixes that. And most importantly no corruption issues. Maybe it's just because this is only a small test FS, but my production one earlier went through the same process without problems as well. Using btrfs-tools v3.17 and kernel 3.18.21 -- With respect, Roman
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