linux-kernel - Re: [RESEND PATCH] fs: avoid mmap sem relocks when coredumping with many missing pages

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Message-ID: <20250120-knabbern-aufwiegen-82ec233f99dd@brauner>
Date: Mon, 20 Jan 2025 15:51:15 +0100
From: Christian Brauner <brauner@...nel.org>
To: Mateusz Guzik <mjguzik@...il.com>
Cc: Christian Brauner <brauner@...nel.org>,
	viro@...iv.linux.org.uk,
	jack@...e.cz,
	linux-kernel@...r.kernel.org,
	linux-fsdevel@...r.kernel.org,
	tavianator@...ianator.com,
	linux-mm@...ck.org,
	akpm@...ux-foundation.org
Subject: Re: [RESEND PATCH] fs: avoid mmap sem relocks when coredumping with many missing pages

On Sun, 19 Jan 2025 11:32:05 +0100, Mateusz Guzik wrote:
> Dumping processes with large allocated and mostly not-faulted areas is
> very slow.
> 
> Borrowing a test case from Tavian Barnes:
> 
> int main(void) {
>     char *mem = mmap(NULL, 1ULL << 40, PROT_READ | PROT_WRITE,
>             MAP_ANONYMOUS | MAP_NORESERVE | MAP_PRIVATE, -1, 0);
>     printf("%p %m\n", mem);
>     if (mem != MAP_FAILED) {
>             mem[0] = 1;
>     }
>     abort();
> }
> 
> [...]

Applied to the vfs-6.15.misc branch of the vfs/vfs.git tree.
Patches in the vfs-6.15.misc branch should appear in linux-next soon.

Please report any outstanding bugs that were missed during review in a
new review to the original patch series allowing us to drop it.

It's encouraged to provide Acked-bys and Reviewed-bys even though the
patch has now been applied. If possible patch trailers will be updated.

Note that commit hashes shown below are subject to change due to rebase,
trailer updates or similar. If in doubt, please check the listed branch.

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs.git
branch: vfs-6.15.misc

[1/1] fs: avoid mmap sem relocks when coredumping with many missing pages
      https://git.kernel.org/vfs/vfs/c/dbdd2935ed48