linux-kernel - Re: [PATCH] fs/proc/base: use maple tree iterators in place of linked list

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Date:   Thu, 25 Aug 2022 09:01:32 -0700
From:   Davidlohr Bueso <dave@...olabs.net>
To:     Liam Howlett <liam.howlett@...cle.com>
Cc:     "maple-tree@...ts.infradead.org" <maple-tree@...ts.infradead.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] fs/proc/base: use maple tree iterators in place of
 linked list

On Wed, 24 Aug 2022, Liam Howlett wrote:

>From: "Liam R. Howlett" <Liam.Howlett@...cle.com>
>
>Use mas_for_each to iterate the list of VMAs instead of a for loop
>across the linked list.

Hmm so why isn't this using the standard VMA_ITERATOR?

>
>Signed-off-by: Liam R. Howlett <Liam.Howlett@...cle.com>
>---
> fs/proc/base.c | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
>
>diff --git a/fs/proc/base.c b/fs/proc/base.c
>index 93f7e3d971e4..0b72a6d8aac3 100644
>--- a/fs/proc/base.c
>+++ b/fs/proc/base.c
>@@ -2350,6 +2350,7 @@ proc_map_files_readdir(struct file *file, struct dir_context *ctx)
> 	GENRADIX(struct map_files_info) fa;
> 	struct map_files_info *p;
> 	int ret;
>+	MA_STATE(mas, NULL, 0, 0);
>
> 	genradix_init(&fa);
>
>@@ -2377,6 +2378,7 @@ proc_map_files_readdir(struct file *file, struct dir_context *ctx)
> 	}
>
> 	nr_files = 0;
>+	mas.tree = &mm->mm_mt;
>
> 	/*
> 	 * We need two passes here:
>@@ -2388,7 +2390,8 @@ proc_map_files_readdir(struct file *file, struct dir_context *ctx)
> 	 * routine might require mmap_lock taken in might_fault().
> 	 */
>
>-	for (vma = mm->mmap, pos = 2; vma; vma = vma->vm_next) {
>+	pos = 2;
>+	mas_for_each(&mas, vma, ULONG_MAX) {
> 		if (!vma->vm_file)
> 			continue;
> 		if (++pos <= ctx->pos)
>-- 
>2.35.1