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Date:   Sun, 20 Dec 2020 05:11:48 +0100
From:   Mike Galbraith <>
To:     Vitaly Wool <>,
        LKML <>,
        linux-mm <>
Cc:     Barry Song <>,
        Sebastian Andrzej Siewior <>,
        Minchan Kim <>,
        NitinGupta <>
Subject: Re: [PATCH] zsmalloc: do not use bit_spin_lock

On Sun, 2020-12-20 at 02:23 +0100, Mike Galbraith wrote:
> On Sun, 2020-12-20 at 02:22 +0200, Vitaly Wool wrote:
> > zsmalloc takes bit spinlock in its _map() callback and releases it
> > only in unmap() which is unsafe and leads to zswap complaining
> > about scheduling in atomic context.
> >
> > To fix that and to improve RT properties of zsmalloc, remove that
> > bit spinlock completely and use a bit flag instead.
> It also does get_cpu_var() in map(), put_cpu_var() in unmap().

Bah, I forgot to mention the config dependent rwlock, it's held across
map()/unmap() as well, so there are two more hurdles, not one.


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