linux-kernel - Re: [PATCH v3 5/5] mm/slub: do not create dma-kmalloc if no managed pages in DMA zone

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Message-ID: <20211214163124.GA21762@lst.de>
Date:   Tue, 14 Dec 2021 17:31:24 +0100
From:   Christoph Hellwig <hch@....de>
To:     Baoquan He <bhe@...hat.com>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        akpm@...ux-foundation.org, hch@....de, cl@...ux.com,
        John.p.donnelly@...cle.com, kexec@...ts.infradead.org,
        stable@...r.kernel.org, Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Vlastimil Babka <vbabka@...e.cz>
Subject: Re: [PATCH v3 5/5] mm/slub: do not create dma-kmalloc if no
 managed pages in DMA zone

On Mon, Dec 13, 2021 at 08:27:12PM +0800, Baoquan He wrote:
> Dma-kmalloc will be created as long as CONFIG_ZONE_DMA is enabled.
> However, it will fail if DMA zone has no managed pages. The failure
> can be seen in kdump kernel of x86_64 as below:

Please just switch the sr allocation to use GFP_KERNEL without GFP_DMA.
The block layer will do the proper bounce buffering underneath for the
very unlikely case that we're actually using the single HBA driver that
has ISA DMA addressing limitations.

Same for the ch drive, btw.