linux-kernel - Re: Possible 6.5 regression: Huge values for "commited memory"

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Message-ID: <CAHk-=wjrEjaUw3oFVEYpF=AWAwrSM3sQTQHuPfFjFdQsvQxHeg@mail.gmail.com>
Date:   Sat, 16 Sep 2023 14:17:09 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Bagas Sanjaya <bagasdotme@...il.com>,
        Michael Labiuk <michael.labiuk@...tuozzo.com>,
        Christoph Biedl <linux-kernel.bfrz@...chmal.in-ulm.de>
Cc:     Linux PARISC <linux-parisc@...r.kernel.org>,
        Linux Memory Management List <linux-mm@...ck.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux Regressions <regressions@...ts.linux.dev>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "Liam R. Howlett" <Liam.Howlett@...cle.com>,
        "Matthew Wilcox (Oracle)" <willy@...radead.org>
Subject: Re: Possible 6.5 regression: Huge values for "commited memory"

On Sat, 16 Sept 2023 at 12:31, Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
>
> Does the attached patch fix the problem?

So while I didn't confirm the fix myself, I'm pretty sure that was it.
Getting the return value wrong would cause an incorrect extra
vm_acct_memory() call in the non-error case when VM_ACCOUNT is set
(and mean the loss of one in the error case, but the error case never
happens in practice).

Which then causes 'vm_committed_as' to grow when it shouldn't, and
causes exactly that "Committed_AS" in /proc/meminfo to be off.

So here's the same patch, but now with a proper commit message etc.

I haven't pushed it out (because it would be lovely to get a
"Tested-by" for it, and that will make the commit ID change), but I'll
probably do so later today, with or without confirmation, because it
does seem to be the problem.

              Linus

View attachment "0001-vm-fix-move_vma-memory-accounting-being-off.patch" of type "text/x-patch" (2297 bytes)