diff mbox series

[v2,3/3] mm: handling Non-LRU pages returned by follow_page

Message ID 20220814140534.363348-4-haiyue.wang@intel.com (mailing list archive)
State Superseded
Headers show
Series fix follow_page related issues | expand

Commit Message

Wang, Haiyue Aug. 14, 2022, 2:05 p.m. UTC
Add the missed put_page handling for handling Non-LRU pages returned by
follow_page with FOLL_GET flag set.

This is the second patch for fixing the commit
3218f8712d6b ("mm: handling Non-LRU pages returned by vm_normal_pages")

Signed-off-by: Haiyue Wang <haiyue.wang@intel.com>
---
 mm/huge_memory.c |  2 +-
 mm/ksm.c         | 10 ++++++++++
 mm/migrate.c     |  6 +++++-
 3 files changed, 16 insertions(+), 2 deletions(-)

Comments

David Hildenbrand Aug. 14, 2022, 4:34 p.m. UTC | #1
On 14.08.22 16:05, Haiyue Wang wrote:
> Add the missed put_page handling for handling Non-LRU pages returned by
> follow_page with FOLL_GET flag set.
> 
> This is the second patch for fixing the commit
> 3218f8712d6b ("mm: handling Non-LRU pages returned by vm_normal_pages")
> 
> Signed-off-by: Haiyue Wang <haiyue.wang@intel.com>
> ---
>  mm/huge_memory.c |  2 +-
>  mm/ksm.c         | 10 ++++++++++
>  mm/migrate.c     |  6 +++++-
>  3 files changed, 16 insertions(+), 2 deletions(-)
> 
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index 2ee6d38a1426..b2ba17c3dcd7 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -2966,7 +2966,7 @@ static int split_huge_pages_pid(int pid, unsigned long vaddr_start,
>  		if (IS_ERR_OR_NULL(page))
>  			continue;
>  
> -		if (!is_transparent_hugepage(page))
> +		if (is_zone_device_page(page) || !is_transparent_hugepage(page))
>  			goto next;
>  
>  		total++;
> diff --git a/mm/ksm.c b/mm/ksm.c
> index fe3e0a39f73a..1360bb52ada6 100644
> --- a/mm/ksm.c
> +++ b/mm/ksm.c
> @@ -477,6 +477,10 @@ static int break_ksm(struct vm_area_struct *vma, unsigned long addr)
>  				FOLL_GET | FOLL_MIGRATION | FOLL_REMOTE);
>  		if (IS_ERR_OR_NULL(page))
>  			break;
> +		if (is_zone_device_page(page)) {
> +			put_page(page);
> +			break;
> +		}

I think we can drop this check completely. While working on patches that
touch this code I realized that this check is completely useless. device
pages are never PageKsm pages and there is no need to special-case here.

If a zone device page could be PageKsm, then we wouldn't handle it here
correctly and not break ksm.

So just drop it.
Wang, Haiyue Aug. 15, 2022, 1:03 a.m. UTC | #2
> -----Original Message-----
> From: David Hildenbrand <david@redhat.com>
> Sent: Monday, August 15, 2022 00:34
> To: Wang, Haiyue <haiyue.wang@intel.com>; linux-mm@kvack.org; linux-kernel@vger.kernel.org
> Cc: akpm@linux-foundation.org; linmiaohe@huawei.com; Huang, Ying <ying.huang@intel.com>;
> songmuchun@bytedance.com; naoya.horiguchi@linux.dev; alex.sierra@amd.com
> Subject: Re: [PATCH v2 3/3] mm: handling Non-LRU pages returned by follow_page
> 
> On 14.08.22 16:05, Haiyue Wang wrote:
> > Add the missed put_page handling for handling Non-LRU pages returned by
> > follow_page with FOLL_GET flag set.
> >
> > This is the second patch for fixing the commit
> > 3218f8712d6b ("mm: handling Non-LRU pages returned by vm_normal_pages")
> >
> > Signed-off-by: Haiyue Wang <haiyue.wang@intel.com>
> > ---
> >  mm/huge_memory.c |  2 +-
> >  mm/ksm.c         | 10 ++++++++++
> >  mm/migrate.c     |  6 +++++-
> >  3 files changed, 16 insertions(+), 2 deletions(-)
> >
> > diff --git a/mm/ksm.c b/mm/ksm.c
> > index fe3e0a39f73a..1360bb52ada6 100644
> > --- a/mm/ksm.c
> > +++ b/mm/ksm.c
> > @@ -477,6 +477,10 @@ static int break_ksm(struct vm_area_struct *vma, unsigned long addr)
> >  				FOLL_GET | FOLL_MIGRATION | FOLL_REMOTE);
> >  		if (IS_ERR_OR_NULL(page))
> >  			break;
> > +		if (is_zone_device_page(page)) {
> > +			put_page(page);
> > +			break;
> > +		}
> 
> I think we can drop this check completely. While working on patches that
> touch this code I realized that this check is completely useless. device
> pages are never PageKsm pages and there is no need to special-case here.
> 
> If a zone device page could be PageKsm, then we wouldn't handle it here
> correctly and not break ksm.
> 
> So just drop it.
> 

Fixed in v3.

> 
> 
> --
> Thanks,
> 
> David / dhildenb
diff mbox series

Patch

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 2ee6d38a1426..b2ba17c3dcd7 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2966,7 +2966,7 @@  static int split_huge_pages_pid(int pid, unsigned long vaddr_start,
 		if (IS_ERR_OR_NULL(page))
 			continue;
 
-		if (!is_transparent_hugepage(page))
+		if (is_zone_device_page(page) || !is_transparent_hugepage(page))
 			goto next;
 
 		total++;
diff --git a/mm/ksm.c b/mm/ksm.c
index fe3e0a39f73a..1360bb52ada6 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -477,6 +477,10 @@  static int break_ksm(struct vm_area_struct *vma, unsigned long addr)
 				FOLL_GET | FOLL_MIGRATION | FOLL_REMOTE);
 		if (IS_ERR_OR_NULL(page))
 			break;
+		if (is_zone_device_page(page)) {
+			put_page(page);
+			break;
+		}
 		if (PageKsm(page))
 			ret = handle_mm_fault(vma, addr,
 					      FAULT_FLAG_WRITE | FAULT_FLAG_REMOTE,
@@ -562,10 +566,13 @@  static struct page *get_mergeable_page(struct rmap_item *rmap_item)
 	page = follow_page(vma, addr, FOLL_GET);
 	if (IS_ERR_OR_NULL(page))
 		goto out;
+	if (is_zone_device_page(page))
+		goto out_putpage;
 	if (PageAnon(page)) {
 		flush_anon_page(vma, page, addr);
 		flush_dcache_page(page);
 	} else {
+out_putpage:
 		put_page(page);
 out:
 		page = NULL;
@@ -2313,6 +2320,8 @@  static struct rmap_item *scan_get_next_rmap_item(struct page **page)
 				cond_resched();
 				continue;
 			}
+			if (is_zone_device_page(*page))
+				goto next_page;
 			if (PageAnon(*page)) {
 				flush_anon_page(vma, *page, ksm_scan.address);
 				flush_dcache_page(*page);
@@ -2327,6 +2336,7 @@  static struct rmap_item *scan_get_next_rmap_item(struct page **page)
 				mmap_read_unlock(mm);
 				return rmap_item;
 			}
+next_page:
 			put_page(*page);
 			ksm_scan.address += PAGE_SIZE;
 			cond_resched();
diff --git a/mm/migrate.c b/mm/migrate.c
index 5d304de3950b..fee12cd2f294 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -1675,6 +1675,9 @@  static int add_page_for_migration(struct mm_struct *mm, unsigned long addr,
 	if (!page)
 		goto out;
 
+	if (is_zone_device_page(page))
+		goto out_putpage;
+
 	err = 0;
 	if (page_to_nid(page) == node)
 		goto out_putpage;
@@ -1869,7 +1872,8 @@  static void do_pages_stat_array(struct mm_struct *mm, unsigned long nr_pages,
 			goto set_status;
 
 		if (page) {
-			err = page_to_nid(page);
+			err = !is_zone_device_page(page) ? page_to_nid(page)
+							 : -ENOENT;
 			if (foll_flags & FOLL_GET)
 				put_page(page);
 		} else {