linux-kernel - Re: [PATCH 2/2] uprobe: collapse THP pmd after removing all uprobes

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Message-ID: <CA691086-51F2-47AD-B280-8A9F9CF91804@fb.com>
Date:   Wed, 31 Jul 2019 16:36:15 +0000
From:   Song Liu <songliubraving@...com>
To:     Oleg Nesterov <oleg@...hat.com>
CC:     lkml <linux-kernel@...r.kernel.org>, Linux-MM <linux-mm@...ck.org>,
        "Andrew Morton" <akpm@...ux-foundation.org>,
        Matthew Wilcox <matthew.wilcox@...cle.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Kernel Team <Kernel-team@...com>,
        "William Kucharski" <william.kucharski@...cle.com>,
        "srikar@...ux.vnet.ibm.com" <srikar@...ux.vnet.ibm.com>
Subject: Re: [PATCH 2/2] uprobe: collapse THP pmd after removing all uprobes



> On Jul 31, 2019, at 9:16 AM, Oleg Nesterov <oleg@...hat.com> wrote:
> 
> On 07/28, Song Liu wrote:
>> 
>> @@ -525,6 +527,9 @@ int uprobe_write_opcode(struct arch_uprobe *auprobe, struct mm_struct *mm,
>> 
>> 				/* dec_mm_counter for old_page */
>> 				dec_mm_counter(mm, MM_ANONPAGES);
>> +
>> +				if (PageCompound(orig_page))
>> +					orig_page_huge = true;
> 
> I am wondering how find_get_page() can return a PageCompound() page...
> 
> IIUC, this is only possible if shmem_file(), right?

Yes, this is the case at the moment. We will be able to do it for other
file systems when this set gets in: 

	https://lkml.org/lkml/2019/6/24/1531

Thanks,
Song