linux-kernel - Re: [REGRESSION] "split bio_kmalloc from bio_alloc_bioset" causing crash shortly after bootup

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Date:   Tue, 23 Feb 2021 08:11:48 +0100
From:   Christoph Hellwig <hch@....de>
To:     John Stultz <john.stultz@...aro.org>
Cc:     Chaitanya Kulkarni <Chaitanya.Kulkarni@....com>,
        David Anderson <dvander@...gle.com>,
        Christoph Hellwig <hch@....de>,
        Johannes Thumshirn <Johannes.Thumshirn@....com>,
        Damien Le Moal <Damien.LeMoal@....com>,
        Jens Axboe <axboe@...nel.dk>,
        Alistair Delva <adelva@...gle.com>,
        Todd Kjos <tkjos@...gle.com>,
        Amit Pundir <amit.pundir@...aro.org>,
        YongQin Liu <yongqin.liu@...aro.org>,
        lkml <linux-kernel@...r.kernel.org>,
        "linux-block@...r.kernel.org" <linux-block@...r.kernel.org>
Subject: Re: [REGRESSION] "split bio_kmalloc from bio_alloc_bioset" causing
 crash shortly after bootup

On Mon, Feb 22, 2021 at 08:22:09PM -0800, John Stultz wrote:
> I'm wondering if given there are multiple call sites, that in
> bio_alloc_bioset() would something like the following make more sense?
> (apologies, copy pasted so this is whitespace corrupted)
> thanks

No.  The fallback from the mempool backing to plain kmalloc is highly
dangerous, which is one of the reasons it was removed.  The other being
that we don't want to disturb the fast path with this slow path.