https://bugs.freedesktop.org/show_bug.cgi?id=104082
--- Comment #40 from Jean Delvare jdelvare@suse.de --- I believe there are 2 incarnations of this bug, with the same symptoms but different root causes.
The first bug is affecting kernels v4.14 and v4.15, it is caused by 2 MB allocations failing too verbosely when in fact 4 kB allocations worked just fine as a fallback. That one is fixed in v4.16 by:
commit d0bc0c2a31c95002d37c3cc511ffdcab851b3256 Author: Christian König Date: Thu Jan 4 14:24:19 2018 +0100
swiotlb: suppress warning when __GFP_NOWARN is set
However kernel v4.16 also includes the following commit:
commit 0176adb004065d6815a8e67946752df4cd947c5b Author: Christoph Hellwig Date: Tue Jan 9 22:15:30 2018 +0100
swiotlb: refactor coherent buffer allocation
which contains a bug producing exactly the same backtraces. That bug is caused by an improper check of the result of dma_coherent_ok(), which was fixed 10 days ago with:
commit 9e7f06c8beee304ee21b791653fefcd713f48b9a Author: Takashi Iwai Date: Tue Apr 10 19:05:13 2018 +0200
swiotlb: fix unexpected swiotlb_alloc_coherent failures
I backported this fix on top of v4.16.3 and the backtraces are gone. The commit was tagged for stable inclusion so I expect it to be included in v4.16.