linux-kernel - Re: [RFC PATCH 0/2] mm: continue using per-VMA lock when retrying page faults after I/O

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Message-ID: <aSfO7fA-04SBtTug@casper.infradead.org>
Date: Thu, 27 Nov 2025 04:09:17 +0000
From: Matthew Wilcox <willy@...radead.org>
To: Barry Song <21cnbao@...il.com>
Cc: akpm@...ux-foundation.org, linux-mm@...ck.org,
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Subject: Re: [RFC PATCH 0/2] mm: continue using per-VMA lock when retrying
 page faults after I/O

On Thu, Nov 27, 2025 at 09:14:36AM +0800, Barry Song wrote:
> There is no need to always fall back to mmap_lock if the per-VMA
> lock was released only to wait for pagecache or swapcache to
> become ready.

Something I've been wondering about is removing all the "drop the MM
locks while we wait for I/O" gunk.  It's a nice amount of code removed:

 include/linux/pagemap.h |  8 +---
 mm/filemap.c            | 98 ++++++++++++-------------------------------------
 mm/internal.h           | 21 -----------
 mm/memory.c             | 13 +------
 mm/shmem.c              |  6 ---
 5 files changed, 27 insertions(+), 119 deletions(-)

and I'm not sure we still need to do it with per-VMA locks.  What I
have here doesn't boot and I ran out of time to debug it.