netdev - Re: [PATCH 22/22] mtd: rawnand: Use dma_alloc

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Message-ID: <20220219071900.GH26711@lst.de>
Date:   Sat, 19 Feb 2022 08:19:00 +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,
        42.hyeyoo@...il.com, penberg@...nel.org, rientjes@...gle.com,
        iamjoonsoo.kim@....com, vbabka@...e.cz, David.Laight@...LAB.COM,
        david@...hat.com, herbert@...dor.apana.org.au, davem@...emloft.net,
        linux-crypto@...r.kernel.org, steffen.klassert@...unet.com,
        netdev@...r.kernel.org, hca@...ux.ibm.com, gor@...ux.ibm.com,
        agordeev@...ux.ibm.com, borntraeger@...ux.ibm.com,
        svens@...ux.ibm.com, linux-s390@...r.kernel.org, michael@...le.cc,
        linux-i2c@...r.kernel.org, wsa@...nel.org
Subject: Re: [PATCH 22/22] mtd: rawnand: Use dma_alloc_noncoherent() for
 dma buffer

On Sat, Feb 19, 2022 at 08:52:21AM +0800, Baoquan He wrote:
> Use dma_alloc_noncoherent() instead of directly allocating buffer
> from kmalloc with GFP_DMA. DMA API will try to allocate buffer
> depending on devices addressing limitation.

I think it would be better to still allocate the buffer at allocation
time and then just transfer ownership using dma_sync_single* in the I/O
path to avoid the GFP_ATOMIC allocation.