linux-kernel - Re: [PATCH 1/7] ubi: block: Refactor sg list processing for highmem

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Message-ID: <164102534.5258032.1691697286622.JavaMail.zimbra@nod.at>
Date:   Thu, 10 Aug 2023 21:54:46 +0200 (CEST)
From:   Richard Weinberger <richard@....at>
To:     Christoph Hellwig <hch@...radead.org>
Cc:     linux-mtd <linux-mtd@...ts.infradead.org>,
        Stephan Wurm <stephan.wurm@...berle.de>,
        stable <stable@...r.kernel.org>,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        Vignesh Raghavendra <vigneshr@...com>,
        Oliver Neukum <oliver@...kum.org>,
        Ali Akcaagac <aliakc@....de>,
        Jamie Lenehan <lenehan@...bble.org>,
        James Bottomley <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        Ezequiel Garcia <ezequiel@...guardiasur.com.ar>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        linux-scsi <linux-scsi@...r.kernel.org>
Subject: Re: [PATCH 1/7] ubi: block: Refactor sg list processing for highmem

----- Ursprüngliche Mail -----
> Von: "Christoph Hellwig" <hch@...radead.org>
> An: "richard" <richard@....at>
> On Thu, Aug 10, 2023 at 06:15:36PM +0200, Richard Weinberger wrote:
>> >> The followup patches in this series will switch to kmap_sg()
>> >> and we can remove our own helper and the bounce buffer.
>> > 
>> > Please just use kmap_local and avoid the bounce buffering.
>> 
>> Patch 6 does this.
> 
> But why add the bounce buffering first if you can avoid it from the
> very beginning by just using kmap_local instead of adding a new
> caller for the deprecate kmap_atomic?

Because I want this fix also in all stable trees. kmap_local() is rather
new. When back porting patch 1/7, bounce buffers and kmap_atomic()
are needed anyway.
By doing this in patch 1/7 I avoid backport troubles and keep the
delta between upstream and stable trees minimal.

Thanks,
//richard