linux-kernel - Re: [PATCH 1/2] mm/vmalloc: Introduce vmap

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Message-ID: <CAOzc2pwCOfniCESzhNg9WE73YXQL7516Fya4Rrwij4CfWSt+Lg@mail.gmail.com>
Date: Mon, 3 Feb 2025 11:23:07 -0800
From: Vishal Moola <vishal.moola@...il.com>
To: Christoph Hellwig <hch@...radead.org>
Cc: akpm@...ux-foundation.org, linux-mm@...ck.org, 
	linux-kernel@...r.kernel.org, urezki@...il.com, 
	intel-gfx@...ts.freedesktop.org
Subject: Re: [PATCH 1/2] mm/vmalloc: Introduce vmap_file()

On Thu, Jan 30, 2025 at 11:09 PM Christoph Hellwig <hch@...radead.org> wrote:
>
> On Thu, Jan 30, 2025 at 04:18:05PM -0800, Vishal Moola (Oracle) wrote:
> > +     rcu_read_lock();
> > +     xas_for_each(&xas, folio, last) {
>
> This only maps folios currently in the page cache, which makes it
> usefull for everything except ramfs-style purely in-memory file systems.
> I.e. for the shmem use case in the second patch it fails to swap in
> swapped out tmpfs folios.

Ah, I see. I can drop that patch then. Its primary purpose was to provide a
user for vmap_file(). As you've pointed out, that won't work with tmpfs or
anon pages. I'll hold off on a v2 until there are better usecases for
vmap_file().

> > +EXPORT_SYMBOL(vmap_file);
>
> EXPORT_SYMBOL_GPL for any advances vmalloc-layer functionality, please.

Ok, I'll keep that in mind in the future.