Re: [4.7.0rc6] Page Allocation Failures with dm-crypt

From: Matthias Dahl
Date: Mon Jul 11 2016 - 04:31:30 EST


I made a few more tests and here my observations:

- kernels 4.4.8 and 4.5.5 show the same behavior

- the moment dd starts, memory usage spikes rapidly and within a just
a few seconds has filled up all 32 GiB of RAM

- dd w/ direct i/o works just fine

- mkfs.ext4 unfortunately shows the same behavior as dd w/o direct i/o
and such makes creation of an ext4 fs on dm-crypt a game of luck

(much more exposed so with e2fsprogs 1.43.1)

I am kind of puzzled that this bug has seemingly gone so long unnoticed
since it is rather severe and makes dm-crypt unusable to a certain degree
for fs encryption (or at least the initial creation of the fs). Am I
missing something here or doing something terribly stupid?

With Kind Regards from Germany

Dipl.-Inf. (FH) Matthias Dahl | Software Engineer |
services: custom software [desktop, mobile, web], server administration