linux-kernel - Re: linux-next: Tree for Aug 7 (mm/khugepaged.c)

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Date:   Wed, 7 Aug 2019 22:11:28 +0000
From:   Song Liu <songliubraving@...com>
To:     Randy Dunlap <rdunlap@...radead.org>
CC:     Andrew Morton <akpm@...ux-foundation.org>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        Linux Next Mailing List <linux-next@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux MM <linux-mm@...ck.org>
Subject: Re: linux-next: Tree for Aug 7 (mm/khugepaged.c)



> On Aug 7, 2019, at 2:30 PM, Randy Dunlap <rdunlap@...radead.org> wrote:
> 
> On 8/7/19 2:27 PM, Andrew Morton wrote:
>> On Wed, 7 Aug 2019 21:00:04 +0000 Song Liu <songliubraving@...com> wrote:
>> 
>>>>> 
>>>>> Shall I resend the patch, or shall I send fix on top of current patch?
>>>> 
>>>> Either is OK.  If the difference is small I will turn it into an
>>>> incremental patch so that I (and others) can see what changed.
>>> 
>>> Please find the patch to fix this at the end of this email. It applies 
>>> right on top of "khugepaged: enable collapse pmd for pte-mapped THP". 
>>> It may conflict a little with the "Enable THP for text section of 
>>> non-shmem files" set, which renames function khugepaged_scan_shmem(). 
>>> 
>>> Also, I found v3 of the set in linux-next. The latest is v4:
>>> 
>>> https://lkml.org/lkml/2019/8/2/1587
>>> https://lkml.org/lkml/2019/8/2/1588
>>> https://lkml.org/lkml/2019/8/2/1589
>> 
>> It's all a bit confusing.  I'll drop 
>> 
>> mm-move-memcmp_pages-and-pages_identical.patch
>> uprobe-use-original-page-when-all-uprobes-are-removed.patch
>> uprobe-use-original-page-when-all-uprobes-are-removed-v2.patch
>> mm-thp-introduce-foll_split_pmd.patch
>> mm-thp-introduce-foll_split_pmd-v11.patch
>> uprobe-use-foll_split_pmd-instead-of-foll_split.patch
>> khugepaged-enable-collapse-pmd-for-pte-mapped-thp.patch
>> uprobe-collapse-thp-pmd-after-removing-all-uprobes.patch
>> 
>> Please resolve Oleg's review comments and resend everything.
>> 
> 
> OK, that will take care of the build error that I am still seeing
> when SHMEM is not enabled:
> 
> ../mm/khugepaged.c:1849:2: note: in expansion of macro ‘BUILD_BUG’
>  BUILD_BUG();
>  ^~~~~~~~~

This was broken by one of my other patch. Sorry!

The following patch (on top of linux-next/master) fixes it. 

Thanks,
Song

================= 8< ==============================

From 4d6e3a3a28bf85b1debbb90c55f66c81e9ebb9ec Mon Sep 17 00:00:00 2001
From: Song Liu <songliubraving@...com>
Date: Wed, 7 Aug 2019 14:57:38 -0700
Subject: [PATCH] khugepaged: fix build without CONFIG_SHMEM

khugepaged_scan_file() should be fully bypassed without CONFIG_SHMEM.

Fixes: f57286140d96 ("mm,thp: add read-only THP support for (non-shmem) FS")
Signed-off-by: Song Liu <songliubraving@...com>
---
 mm/khugepaged.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 272fed3ed0f0..40c25ddf29e4 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -1778,7 +1778,7 @@ static unsigned int khugepaged_scan_mm_slot(unsigned int pages,
                        VM_BUG_ON(khugepaged_scan.address < hstart ||
                                  khugepaged_scan.address + HPAGE_PMD_SIZE >
                                  hend);
-                       if (vma->vm_file) {
+                       if (IS_ENABLED(CONFIG_SHMEM) && vma->vm_file) {
                                struct file *file;
                                pgoff_t pgoff = linear_page_index(vma,
                                                khugepaged_scan.address);
--
2.17.1