From: Andrew Morton <akpm@linux-foundation.org>
To: "Zach O'Keefe" <zokeefe@google.com>
Cc: linux-mm@kvack.org, Hugh Dickins <hughd@google.com>,
Yang Shi <shy828301@gmail.com>
Subject: Re: [PATCH] mm/MADV_COLLAPSE: don't expand collapse when vm_end is past requested end
Date: Thu, 22 Dec 2022 16:56:52 -0800 [thread overview]
Message-ID: <20221222165652.3775ff5343580e02ffabfa23@linux-foundation.org> (raw)
In-Reply-To: <20221223003953.2795313-1-zokeefe@google.com>
On Thu, 22 Dec 2022 16:39:53 -0800 "Zach O'Keefe" <zokeefe@google.com> wrote:
> MADV_COLLAPSE acts on one hugepage-aligned/sized region at a time, until
> it has collapsed all eligible memory contained within the bounds
> supplied by the user.
>
> At the top of each hugepage iteration we (re)lock mmap_lock and
> (re)validate the VMA for eligibility and update variables that might
> have changed while mmap_lock was dropped. One thing that might occur,
> is that the VMA could be resized, and as such, we refetch vma->vm_end
> to make sure we don't collapse past the end of the VMA.
>
> However, it's possible that during this refetch that we expand the
> region acted on by MADV_COLLAPSE if vma->vm_end is greater than the end
> of the user-supplied range.
>
> Don't expand the acted-on region when refetching vma->vm_end.
What are the user-visible effects of this?
> Fixes: 4d24de9425f7 ("mm: MADV_COLLAPSE: refetch vm_end after reacquiring mmap_lock")
Should we backport "mm/shmem: restore SHMEM_HUGE_DENY precedence over
MADV_COLLAPSE" and/or this patch into 6.1.x?
next prev parent reply other threads:[~2022-12-23 0:56 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-12-23 0:39 Zach O'Keefe
2022-12-23 0:56 ` Andrew Morton [this message]
2022-12-23 1:25 ` Hugh Dickins
2022-12-23 1:33 ` Zach O'Keefe
2022-12-23 18:06 ` Andrew Morton
2022-12-23 20:51 ` Zach O'Keefe
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