linux-kernel - Re: [PATCH v4 3/5] mm, thp: introduce FOLL_SPLIT

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Message-ID: <6D00E9F1-A81D-44B8-9504-3B7B440CF093@fb.com>
Date:   Fri, 21 Jun 2019 14:08:44 +0000
From:   Song Liu <songliubraving@...com>
To:     "Kirill A. Shutemov" <kirill@...temov.name>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "oleg@...hat.com" <oleg@...hat.com>,
        "rostedt@...dmis.org" <rostedt@...dmis.org>,
        "mhiramat@...nel.org" <mhiramat@...nel.org>,
        "matthew.wilcox@...cle.com" <matthew.wilcox@...cle.com>,
        "kirill.shutemov@...ux.intel.com" <kirill.shutemov@...ux.intel.com>,
        Kernel Team <Kernel-team@...com>
Subject: Re: [PATCH v4 3/5] mm, thp: introduce FOLL_SPLIT_PMD



> On Jun 21, 2019, at 5:44 AM, Kirill A. Shutemov <kirill@...temov.name> wrote:
> 
> On Thu, Jun 13, 2019 at 10:57:45AM -0700, Song Liu wrote:
>> @@ -419,6 +419,11 @@ static struct page *follow_pmd_mask(struct vm_area_struct *vma,
>> 			put_page(page);
>> 			if (pmd_none(*pmd))
>> 				return no_page_table(vma, flags);
>> +		} else {  /* flags & FOLL_SPLIT_PMD */
>> +			spin_unlock(ptl);
>> +			ret = 0;
>> +			split_huge_pmd(vma, pmd, address);
>> +			pte_alloc(mm, pmd);
> 
> pte_alloc() can fail and the failure should be propogated to the caller.

Good catch! Fixing it now. 

Thanks,
Song