On 2017年12月06日 03:22, Benjamin Beichler wrote: > Hi, > > I have a setup as following: (1,7TB drive + 128GB SSD in Bcache) <==> > luks device <==> btrfs FS > I have been running Arch linux with newest stable kernel 4.14. > > After a reboot last week my btrfs volume becomes unmountable, because > of checksum errors in the chunk root. > > These are the outputs of check: > "btrfs check /dev/mapper/root > > checksum verify failed on 131072 found 1A98EC4A wanted B97166DB > checksum verify failed on 131072 found 1A98EC4A wanted B97166DB > bytenr mismatch, want=131072, have=9229526874648754029 > ERROR: cannot read chunk root > ERROR: cannot open file system
That's the most serious problem for btrfs. No chunk tree nothing can be recovered. > " > > Most other check/repair commands fail with the same error. The > super-dump can be found here: > https://gist.github.com/anonymous/33bd22696c37355c6cfd093f4c6bd226 Better with -fa option to show system chunk array and backup roots. > > After my attempts in initramfs failed I used a recent arch-live disk > to compile newest btrfs-tools and use recent kernel (4.9) to recover > the chunk tree. > > Therefore I ran the chunk recover command on my drive. It looks like > the following here> > https://gist.github.com/anonymous/5359c08734cf81ad3887b635536d9631 > > for better debugging I already used gdb to inspect the following error: > > "ERROR: tree block bytenr 0 is not aligned to sectorsize 4096" > > but as the exception raise is far to late to inspect the problem. > Since most of my chunks seems to be recoverable, I hope a tree rebuild > is possible, but I don't know how. This seems to be related to __rebuikld_device_items(), where btrfs_insert_item() return -EIO and triggered BUG_ON(). Despite the heavy (and mostly overkilled) method, we can do a lighter version by checking every possible tree root in system chunk array. Which needs the -fa option of super-dump subcommand. The basic idea is: 1) Check the back_roots of output If backup_chunk_root of all backup roots are the same with chunk_root (which is 131072 in your case), skip to step 3) 2) Try all backup_chunk_root numbers with "btrfs check --chunk-root <bytenr>" If some number returns good result (no obvious problem reported), then with --repair option, finish the repair. If all fails, go step 3) 3) Try all bytenr aligned to 16K in system chunk Same "btrfs check --chunk-root <bytenr>" until one returns good result. Then --repair. Thanks, Qu > > Do you have any suggestions? > -- > 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 >
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