[Bug 992480] Re: fsck.btrfs of a 1TB volume triggers OOM kill on a 1GB RAM machine. (32-bit)

[Arie Skliarouk]

I reformatted the 6TB volume, and filled it with data (3.5TB). Yesterday there was a power failure and the partition became corrupted.
btrfsck 0.19+20120328-2ubuntu1 used all available memory (of 6GB present) and got killed by OOM:

...
ref mismatch on [5606072983552 8192] extent item 1, found 0
Incorrect local backref count on 5606072983552 root 4095 owner 14571496 offset 0 found 0 wanted 1 back 0x846449d0
backpointer mismatch on [5606072983552 8192]
owner ref check failed [5606072983552 8192]
Errors found in extent allocation tree
checking fs roots
Killed

I then added 2GB and after using 6.5GB of memory, the btrfsck managed to complete, but it did not fix the filesystem:
Errors found in extent allocation tree
checking fs roots
checking root refs
found 3304564289536 bytes used err is 0
total csum bytes: 3195312740
total tree bytes: 30077300736
total fs tree bytes: 24014831616
btree space waste bytes: 7517736113
file data blocks allocated: 3557121048576
 referenced 3557121048576
Btrfs Btrfs v0.19

Is there a special flag for btrfsck to fix the filesystem?

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Title:
  fsck.btrfs of a 1TB volume triggers OOM kill on a 1GB RAM machine.
  (32-bit)

Status in “btrfs-tools” package in Ubuntu:
  Confirmed

Bug description:
  fsck.btrfs of a 1TB volume triggers OOM kill on a 1GB RAM machine.
  (32-bit)

  Thats about all there is to say:

  sudo fsck -v /dev/sdd1
  fsck from util-linux 2.20.1
  fsck: Warning... fsck.btrfs for device /dev/sdd1 exited with signal 9.

  May  1 17:49:10 lifelesswks kernel: [639863.533203] Out of memory: Kill process 32192 (fsck.btrfs) score 846 or sacrifice child
  May  1 17:49:10 lifelesswks kernel: [639863.533210] Killed process 32192 (fsck.btrfs) total-vm:2555884kB, anon-rss:772228kB, file-rss:0kB

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