linux-kernel - Re: [PATCH 2/2] Deprecate NR_UNSTABLE_NFS, use NR

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Date:   Thu, 2 Apr 2020 08:10:09 -0700
From:   Christoph Hellwig <hch@...radead.org>
To:     NeilBrown <neilb@...e.de>
Cc:     Trond Myklebust <trondmy@...merspace.com>,
        "Anna.Schumaker@...app.com" <Anna.Schumaker@...app.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Jan Kara <jack@...e.cz>, linux-mm@...ck.org,
        linux-nfs@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] Deprecate NR_UNSTABLE_NFS, use NR_WRITEBACK

On Thu, Apr 02, 2020 at 10:54:07AM +1100, NeilBrown wrote:
> 
> After an NFS page has been written it is considered "unstable" until a
> COMMIT request succeeds.  If the COMMIT fails, the page will be
> re-written.
> 
> These "unstable" pages are currently accounted as "reclaimable",
> either in WB_RECLAIMABLE, or in NR_UNSTABLE_NFS which is included in a
> 'reclaimable' count.  This might have made sense when sending the COMMIT
> required a separate action by the VFS/MM (e.g. releasepage() used to
> send a COMMIT).  However now that all writes generated by ->writepages()
> will automatically be followed by a COMMIT, it makes more sense to
> treat them as writeback pages.
> 
> So this page deprecates NR_UNSTABLE_NFS and accounts unstable pages in
> NR_WRITEBACK and WB_WRITEBACK.

Please remove it entirely if it isn't used any more.