linux-kernel - Re: [6.2][regression] after commit ffcb754584603adf7039d7972564fbf6febdc542 all sound devices disappeared (due BUG at mm/page

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Message-ID: <20221216064645.GA24446@lst.de>
Date:   Fri, 16 Dec 2022 07:46:45 +0100
From:   Christoph Hellwig <hch@....de>
To:     Mikhail Gavrilov <mikhail.v.gavrilov@...il.com>
Cc:     Takashi Iwai <tiwai@...e.de>, alsa-devel@...a-project.org,
        hch@....de, m.szyprowski@...sung.com,
        Linux List Kernel Mailing <linux-kernel@...r.kernel.org>,
        Robin Murphy <robin.murphy@....com>, iommu@...ts.linux.dev
Subject: Re: [6.2][regression] after commit
 ffcb754584603adf7039d7972564fbf6febdc542 all sound devices
 disappeared (due BUG at mm/page_alloc.c:3592!)

Ok, it seems like the sound noncontig alloc code that I already
commented on as potentially bogus GFP_GOMP mapping trips this.  I think
for now the right thing would be to revert the hunk in dma-iommu.c
(see patch below).  The other thing to try would be to remove both
uses GFP_COMP in sound/core/memalloc.c, which should have the same
effect.

diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
index 9297b741f5e80e..f798c44e090337 100644
--- a/drivers/iommu/dma-iommu.c
+++ b/drivers/iommu/dma-iommu.c
@@ -744,9 +744,6 @@ static struct page **__iommu_dma_alloc_pages(struct device *dev,
 	/* IOMMU can map any pages, so himem can also be used here */
 	gfp |= __GFP_NOWARN | __GFP_HIGHMEM;
 
-	/* It makes no sense to muck about with huge pages */
-	gfp &= ~__GFP_COMP;
-
 	while (count) {
 		struct page *page = NULL;
 		unsigned int order_size;