On 09/12/2016 02:39 PM, David Sterba wrote: > On Fri, Sep 09, 2016 at 11:37:21PM +0200, Hans van Kranenburg wrote: >> Hi, >> >> While trying to enable skinny metadata on a filesystem, I got this error >> (after minutes of reading from disk by the program): >> >> -# btrfstune -x /dev/xvdb >> extent-tree.c:2688: btrfs_reserve_extent: Assertion `ret` failed. >> btrfstune[0x410ef6] >> btrfstune[0x410f1d] >> btrfstune(btrfs_reserve_extent+0x781)[0x41522e] >> btrfstune(btrfs_alloc_free_block+0x63)[0x415413] >> btrfstune(__btrfs_cow_block+0xfc)[0x409176] >> btrfstune(btrfs_cow_block+0x8b)[0x409718] >> btrfstune[0x40d8ad] >> btrfstune(btrfs_commit_transaction+0xb8)[0x40f10d] >> btrfstune(main+0x3b3)[0x407e31] >> /lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xf0)[0x7f945fa06700] >> btrfstune(_start+0x29)[0x408509] >> >> This is a ~40TiB filesystem that was created about one and a half year >> ago, has grown from 1TiB to this size now and has always been running >> with the Debian 3.16-ckt kernel. >> >> # uname -a >> Linux backups-dolly 4.7.0-1-amd64 #1 SMP Debian 4.7.2-1 (2016-08-28) >> x86_64 GNU/Linux >> >> # btrfs version >> btrfs-progs v4.7.1 >> >> One of the things I already did earlier today was switching to >> space_cache=v2 >> >> Does the shown error ring a bell? What's the next step to debug this? > > It's a bug in the incompat bit handling the free-space-tree. Opening the > filesystem for read-write should not be allowed, but was mistakenly > enabled by me. > >> The filesystem is a clone of the production filesystem (not btrfs clone, >> but lower level, on iSCSI storage) meant to be used for upgrade-testing >> and performance testing, so if anything goes wrong in whatever way, >> there will be no panicing involved. > > The fix is in devel, but it'd mean that writing to a v2-enabled > filesystem will not work (which also means changing some fatures via > btrfstune as it uses the transaction mechanism that needs to cow blocks > and update free space etc). As I replied this morning, I tried it again on a fresh clone of the underlying snapshot, before doing anything else first with it. So that means at that point it's a filesystem that has only seen 3.16 kernels before, and does still have old free space cache in place, no v2 tree. And, it still blows up. -- Hans van Kranenburg -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
