Re: [PATCH v11 4/6] mm: page_isolation: enable arbitrary range page isolation.

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On 25 Apr 2022, at 10:31, Zi Yan wrote:

> From: Zi Yan <ziy@xxxxxxxxxx>
>
> Now start_isolate_page_range() is ready to handle arbitrary range
> isolation, so move the alignment check/adjustment into the function body.
> Do the same for its counterpart undo_isolate_page_range().
> alloc_contig_range(), its caller, can pass an arbitrary range instead of
> a MAX_ORDER_NR_PAGES aligned one.
>
> Signed-off-by: Zi Yan <ziy@xxxxxxxxxx>
> ---
>  mm/page_alloc.c     | 16 ++--------------
>  mm/page_isolation.c | 33 ++++++++++++++++-----------------
>  2 files changed, 18 insertions(+), 31 deletions(-)
>
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 70ddd9a0bcf3..a002cf12eb6c 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -8924,16 +8924,6 @@ void *__init alloc_large_system_hash(const char *tablename,
>  }
>
>  #ifdef CONFIG_CONTIG_ALLOC
> -static unsigned long pfn_max_align_down(unsigned long pfn)
> -{
> -	return ALIGN_DOWN(pfn, MAX_ORDER_NR_PAGES);
> -}
> -
> -static unsigned long pfn_max_align_up(unsigned long pfn)
> -{
> -	return ALIGN(pfn, MAX_ORDER_NR_PAGES);
> -}
> -
>  #if defined(CONFIG_DYNAMIC_DEBUG) || \
>  	(defined(CONFIG_DYNAMIC_DEBUG_CORE) && defined(DYNAMIC_DEBUG_MODULE))
>  /* Usage: See admin-guide/dynamic-debug-howto.rst */
> @@ -9075,8 +9065,7 @@ int alloc_contig_range(unsigned long start, unsigned long end,
>  	 * put back to page allocator so that buddy can use them.
>  	 */
>
> -	ret = start_isolate_page_range(pfn_max_align_down(start),
> -				pfn_max_align_up(end), migratetype, 0, gfp_mask);
> +	ret = start_isolate_page_range(start, end, migratetype, 0, gfp_mask);
>  	if (ret)
>  		goto done;
>
> @@ -9157,8 +9146,7 @@ int alloc_contig_range(unsigned long start, unsigned long end,
>  		free_contig_range(end, outer_end - end);
>
>  done:
> -	undo_isolate_page_range(pfn_max_align_down(start),
> -				pfn_max_align_up(end), migratetype);
> +	undo_isolate_page_range(start, end, migratetype);
>  	return ret;
>  }
>  EXPORT_SYMBOL(alloc_contig_range);
> diff --git a/mm/page_isolation.c b/mm/page_isolation.c
> index 94b3467e5ba2..75e454f5cf45 100644
> --- a/mm/page_isolation.c
> +++ b/mm/page_isolation.c
> @@ -435,7 +435,6 @@ static int isolate_single_pageblock(unsigned long boundary_pfn, gfp_t gfp_flags,
>   * be MIGRATE_ISOLATE.
>   * @start_pfn:		The lower PFN of the range to be isolated.
>   * @end_pfn:		The upper PFN of the range to be isolated.
> - *			start_pfn/end_pfn must be aligned to pageblock_order.
>   * @migratetype:	Migrate type to set in error recovery.
>   * @flags:		The following flags are allowed (they can be combined in
>   *			a bit mask)
> @@ -482,33 +481,33 @@ int start_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn,
>  {
>  	unsigned long pfn;
>  	struct page *page;
> +	/* isolation is done at page block granularity */
> +	unsigned long isolate_start = ALIGN_DOWN(start_pfn, pageblock_nr_pages);
> +	unsigned long isolate_end = ALIGN(end_pfn, pageblock_nr_pages);
>  	int ret;
>
> -	BUG_ON(!IS_ALIGNED(start_pfn, pageblock_nr_pages));
> -	BUG_ON(!IS_ALIGNED(end_pfn, pageblock_nr_pages));
> -
> -	/* isolate [start_pfn, start_pfn + pageblock_nr_pages) pageblock */
> -	ret = isolate_single_pageblock(start_pfn, gfp_flags, false);
> +	/* isolate [isolate_start, isolate_start + pageblock_nr_pages) pageblock */
> +	ret = isolate_single_pageblock(isolate_start, gfp_flags, false);
>  	if (ret)
>  		return ret;
>
> -	/* isolate [end_pfn - pageblock_nr_pages, end_pfn) pageblock */
> -	ret = isolate_single_pageblock(end_pfn, gfp_flags, true);
> +	/* isolate [isolate_end - pageblock_nr_pages, isolate_end) pageblock */
> +	ret = isolate_single_pageblock(isolate_end, gfp_flags, true);
>  	if (ret) {
> -		unset_migratetype_isolate(pfn_to_page(start_pfn), migratetype);
> +		unset_migratetype_isolate(pfn_to_page(isolate_start), migratetype);
>  		return ret;
>  	}
>
>  	/* skip isolated pageblocks at the beginning and end */
> -	for (pfn = start_pfn + pageblock_nr_pages;
> -	     pfn < end_pfn - pageblock_nr_pages;
> +	for (pfn = isolate_start + pageblock_nr_pages;
> +	     pfn < isolate_end - pageblock_nr_pages;
>  	     pfn += pageblock_nr_pages) {
>  		page = __first_valid_page(pfn, pageblock_nr_pages);
>  		if (page && set_migratetype_isolate(page, migratetype, flags,
>  					start_pfn, end_pfn)) {
> -			undo_isolate_page_range(start_pfn, pfn, migratetype);
> +			undo_isolate_page_range(isolate_start, pfn, migratetype);
>  			unset_migratetype_isolate(
> -				pfn_to_page(end_pfn - pageblock_nr_pages),
> +				pfn_to_page(isolate_end - pageblock_nr_pages),
>  				migratetype);
>  			return -EBUSY;
>  		}
> @@ -524,12 +523,12 @@ void undo_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn,
>  {
>  	unsigned long pfn;
>  	struct page *page;
> +	unsigned long isolate_start = ALIGN_DOWN(start_pfn, pageblock_nr_pages);
> +	unsigned long isolate_end = ALIGN(end_pfn, pageblock_nr_pages);
>
> -	BUG_ON(!IS_ALIGNED(start_pfn, pageblock_nr_pages));
> -	BUG_ON(!IS_ALIGNED(end_pfn, pageblock_nr_pages));
>
> -	for (pfn = start_pfn;
> -	     pfn < end_pfn;
> +	for (pfn = isolate_start;
> +	     pfn < isolate_end;
>  	     pfn += pageblock_nr_pages) {
>  		page = __first_valid_page(pfn, pageblock_nr_pages);
>  		if (!page || !is_migrate_isolate_page(page))
> -- 
> 2.35.1

The fixup patch below should be applied to address the infinite loop issue reported by Qian Cai:

diff --git a/mm/page_isolation.c b/mm/page_isolation.c
index 46cbc4621d84..b70a03d9c52b 100644
--- a/mm/page_isolation.c
+++ b/mm/page_isolation.c
@@ -520,12 +520,12 @@ int start_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn,
 	int ret;

 	/* isolate [isolate_start, isolate_start + pageblock_nr_pages) pageblock */
-	ret = isolate_single_pageblock(isolate_start, gfp_flags, false);
+	ret = isolate_single_pageblock(isolate_start, flags, gfp_flags, false);
 	if (ret)
 		return ret;

 	/* isolate [isolate_end - pageblock_nr_pages, isolate_end) pageblock */
-	ret = isolate_single_pageblock(isolate_end, gfp_flags, true);
+	ret = isolate_single_pageblock(isolate_end, flags, gfp_flags, true);
 	if (ret) {
 		unset_migratetype_isolate(pfn_to_page(isolate_start), migratetype);
 		return ret;




The complete commit with the fixup patch applied is:

From 211ef82d35d3a0cf108846a440145688f7cfa21f Mon Sep 17 00:00:00 2001
From: Zi Yan <ziy@xxxxxxxxxx>
Date: Thu, 12 May 2022 20:22:58 -0700
Subject: [PATCH] mm: page_isolation: enable arbitrary range page
 isolation.

Now start_isolate_page_range() is ready to handle arbitrary range
isolation, so move the alignment check/adjustment into the function body.
Do the same for its counterpart undo_isolate_page_range().
alloc_contig_range(), its caller, can pass an arbitrary range instead of a
MAX_ORDER_NR_PAGES aligned one.

Link: https://lkml.kernel.org/r/20220425143118.2850746-5-zi.yan@xxxxxxxx
Signed-off-by: Zi Yan <ziy@xxxxxxxxxx>
Cc: Christophe Leroy <christophe.leroy@xxxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Eric Ren <renzhengeek@xxxxxxxxx>
Cc: kernel test robot <lkp@xxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Cc: Mike Rapoport <rppt@xxxxxxxxxxxxx>
Cc: Minchan Kim <minchan@xxxxxxxxxx>
Cc: Oscar Salvador <osalvador@xxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
 mm/page_alloc.c     | 16 ++--------------
 mm/page_isolation.c | 33 ++++++++++++++++-----------------
 2 files changed, 18 insertions(+), 31 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 76551933bb1d..9a21ea9af35c 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -8959,16 +8959,6 @@ void *__init alloc_large_system_hash(const char *tablename,
 }

 #ifdef CONFIG_CONTIG_ALLOC
-static unsigned long pfn_max_align_down(unsigned long pfn)
-{
-	return ALIGN_DOWN(pfn, MAX_ORDER_NR_PAGES);
-}
-
-static unsigned long pfn_max_align_up(unsigned long pfn)
-{
-	return ALIGN(pfn, MAX_ORDER_NR_PAGES);
-}
-
 #if defined(CONFIG_DYNAMIC_DEBUG) || \
 	(defined(CONFIG_DYNAMIC_DEBUG_CORE) && defined(DYNAMIC_DEBUG_MODULE))
 /* Usage: See admin-guide/dynamic-debug-howto.rst */
@@ -9110,8 +9100,7 @@ int alloc_contig_range(unsigned long start, unsigned long end,
 	 * put back to page allocator so that buddy can use them.
 	 */

-	ret = start_isolate_page_range(pfn_max_align_down(start),
-				pfn_max_align_up(end), migratetype, 0, gfp_mask);
+	ret = start_isolate_page_range(start, end, migratetype, 0, gfp_mask);
 	if (ret)
 		goto done;

@@ -9192,8 +9181,7 @@ int alloc_contig_range(unsigned long start, unsigned long end,
 		free_contig_range(end, outer_end - end);

 done:
-	undo_isolate_page_range(pfn_max_align_down(start),
-				pfn_max_align_up(end), migratetype);
+	undo_isolate_page_range(start, end, migratetype);
 	return ret;
 }
 EXPORT_SYMBOL(alloc_contig_range);
diff --git a/mm/page_isolation.c b/mm/page_isolation.c
index 6b47acaf51f3..706915c9a380 100644
--- a/mm/page_isolation.c
+++ b/mm/page_isolation.c
@@ -472,7 +472,6 @@ static int isolate_single_pageblock(unsigned long boundary_pfn, int flags,
  * be MIGRATE_ISOLATE.
  * @start_pfn:		The lower PFN of the range to be isolated.
  * @end_pfn:		The upper PFN of the range to be isolated.
- *			start_pfn/end_pfn must be aligned to pageblock_order.
  * @migratetype:	Migrate type to set in error recovery.
  * @flags:		The following flags are allowed (they can be combined in
  *			a bit mask)
@@ -519,33 +518,33 @@ int start_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn,
 {
 	unsigned long pfn;
 	struct page *page;
+	/* isolation is done at page block granularity */
+	unsigned long isolate_start = ALIGN_DOWN(start_pfn, pageblock_nr_pages);
+	unsigned long isolate_end = ALIGN(end_pfn, pageblock_nr_pages);
 	int ret;

-	BUG_ON(!IS_ALIGNED(start_pfn, pageblock_nr_pages));
-	BUG_ON(!IS_ALIGNED(end_pfn, pageblock_nr_pages));
-
-	/* isolate [start_pfn, start_pfn + pageblock_nr_pages) pageblock */
-	ret = isolate_single_pageblock(start_pfn, flags, gfp_flags, false);
+	/* isolate [isolate_start, isolate_start + pageblock_nr_pages) pageblock */
+	ret = isolate_single_pageblock(isolate_start, flags, gfp_flags, false);
 	if (ret)
 		return ret;

-	/* isolate [end_pfn - pageblock_nr_pages, end_pfn) pageblock */
-	ret = isolate_single_pageblock(end_pfn, flags, gfp_flags, true);
+	/* isolate [isolate_end - pageblock_nr_pages, isolate_end) pageblock */
+	ret = isolate_single_pageblock(isolate_end, flags, gfp_flags, true);
 	if (ret) {
-		unset_migratetype_isolate(pfn_to_page(start_pfn), migratetype);
+		unset_migratetype_isolate(pfn_to_page(isolate_start), migratetype);
 		return ret;
 	}

 	/* skip isolated pageblocks at the beginning and end */
-	for (pfn = start_pfn + pageblock_nr_pages;
-	     pfn < end_pfn - pageblock_nr_pages;
+	for (pfn = isolate_start + pageblock_nr_pages;
+	     pfn < isolate_end - pageblock_nr_pages;
 	     pfn += pageblock_nr_pages) {
 		page = __first_valid_page(pfn, pageblock_nr_pages);
 		if (page && set_migratetype_isolate(page, migratetype, flags,
 					start_pfn, end_pfn)) {
-			undo_isolate_page_range(start_pfn, pfn, migratetype);
+			undo_isolate_page_range(isolate_start, pfn, migratetype);
 			unset_migratetype_isolate(
-				pfn_to_page(end_pfn - pageblock_nr_pages),
+				pfn_to_page(isolate_end - pageblock_nr_pages),
 				migratetype);
 			return -EBUSY;
 		}
@@ -561,12 +560,12 @@ void undo_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn,
 {
 	unsigned long pfn;
 	struct page *page;
+	unsigned long isolate_start = ALIGN_DOWN(start_pfn, pageblock_nr_pages);
+	unsigned long isolate_end = ALIGN(end_pfn, pageblock_nr_pages);

-	BUG_ON(!IS_ALIGNED(start_pfn, pageblock_nr_pages));
-	BUG_ON(!IS_ALIGNED(end_pfn, pageblock_nr_pages));

-	for (pfn = start_pfn;
-	     pfn < end_pfn;
+	for (pfn = isolate_start;
+	     pfn < isolate_end;
 	     pfn += pageblock_nr_pages) {
 		page = __first_valid_page(pfn, pageblock_nr_pages);
 		if (!page || !is_migrate_isolate_page(page))
-- 
2.35.1



--
Best Regards,
Yan, Zi

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