From: Oleg Nesterov <oleg@redhat.com>
To: Song Liu <songliubraving@fb.com>
Cc: lkml <linux-kernel@vger.kernel.org>,
Linux-MM <linux-mm@kvack.org>,
Andrew Morton <akpm@linux-foundation.org>,
"matthew.wilcox@oracle.com" <matthew.wilcox@oracle.com>,
"kirill.shutemov@linux.intel.com"
<kirill.shutemov@linux.intel.com>,
"peterz@infradead.org" <peterz@infradead.org>,
"rostedt@goodmis.org" <rostedt@goodmis.org>,
Kernel Team <Kernel-team@fb.com>,
"william.kucharski@oracle.com" <william.kucharski@oracle.com>
Subject: Re: [PATCH v8 2/4] uprobe: use original page when all uprobes are removed
Date: Fri, 26 Jul 2019 10:44:23 +0200 [thread overview]
Message-ID: <20190726084423.GA16112@redhat.com> (raw)
In-Reply-To: <A0D24D6F-B649-4B4B-8C33-70B7DCB0D814@fb.com>
On 07/25, Song Liu wrote:
>
> I guess I know the case now. We can probably avoid this with an simp\x10le
> check for old_page == new_page?
better yet, I think we can check PageAnon(old_page) and avoid the unnecessary
__replace_page() in this case. See the patch below.
Anyway, why __replace_page() needs to lock both pages? This doesn't look nice
even if it were correct. I think it can do lock_page(old_page) later.
Oleg.
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -488,6 +488,10 @@ int uprobe_write_opcode(struct arch_uprobe *auprobe, struct mm_struct *mm,
ref_ctr_updated = 1;
}
+ ret = 0;
+ if (!is_register && !PageAnon(old_page))
+ goto put_old;
+
ret = anon_vma_prepare(vma);
if (ret)
goto put_old;
next prev parent reply other threads:[~2019-07-26 8:44 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20190724083600.832091-1-songliubraving@fb.com>
[not found] ` <20190724083600.832091-3-songliubraving@fb.com>
2019-07-24 9:07 ` [PATCH v8 2/4] uprobe: use original page when all uprobes are removed Oleg Nesterov
2019-07-24 9:17 ` Oleg Nesterov
2019-07-24 9:20 ` Song Liu
2019-07-24 11:37 ` Oleg Nesterov
2019-07-24 18:52 ` Song Liu
2019-07-25 8:14 ` Oleg Nesterov
2019-07-25 18:17 ` Song Liu
2019-07-26 6:07 ` Song Liu
2019-07-26 8:44 ` Oleg Nesterov [this message]
2019-07-26 21:19 ` Song Liu
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