The isolate_lru_page() can only return 0 or -EBUSY, and most users did
not care about the negative error of isolate_lru_page(), except one user
in add_page_for_migration(). So we can convert the isolate_lru_page() to
return a boolean value, which can help to make the code more clear when
checking the return value of isolate_lru_page().

Also convert all users' logic of checking the isolation state.

No functional changes intended.

Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
---
 mm/folio-compat.c   | 12 +++---------
 mm/internal.h       |  2 +-
 mm/khugepaged.c     |  2 +-
 mm/memcontrol.c     |  4 ++--
 mm/memory-failure.c |  4 ++--
 mm/memory_hotplug.c |  2 +-
 mm/migrate.c        |  9 ++++++---
 mm/migrate_device.c |  2 +-
 8 files changed, 17 insertions(+), 20 deletions(-)

diff --git a/mm/folio-compat.c b/mm/folio-compat.c
index 540373cf904e..cabcd1de9ecb 100644
--- a/mm/folio-compat.c
+++ b/mm/folio-compat.c
@@ -113,17 +113,11 @@ struct page *grab_cache_page_write_begin(struct address_space *mapping,
 }
 EXPORT_SYMBOL(grab_cache_page_write_begin);
 
-int isolate_lru_page(struct page *page)
+bool isolate_lru_page(struct page *page)
 {
-	bool ret;
-
 	if (WARN_RATELIMIT(PageTail(page), "trying to isolate tail page"))
-		return -EBUSY;
-	ret = folio_isolate_lru((struct folio *)page);
-	if (ret)
-		return 0;
-
-	return -EBUSY;
+		return false;
+	return folio_isolate_lru((struct folio *)page);
 }
 
 void putback_lru_page(struct page *page)
diff --git a/mm/internal.h b/mm/internal.h
index 8645e8496537..fc01fd092ea5 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -187,7 +187,7 @@ pgprot_t __init early_memremap_pgprot_adjust(resource_size_t phys_addr,
 /*
  * in mm/vmscan.c:
  */
-int isolate_lru_page(struct page *page);
+bool isolate_lru_page(struct page *page);
 bool folio_isolate_lru(struct folio *folio);
 void putback_lru_page(struct page *page);
 void folio_putback_lru(struct folio *folio);
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index cee659cfa3c1..8dbc39896811 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -659,7 +659,7 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
 		 * Isolate the page to avoid collapsing an hugepage
 		 * currently in use by the VM.
 		 */
-		if (isolate_lru_page(page)) {
+		if (!isolate_lru_page(page)) {
 			unlock_page(page);
 			result = SCAN_DEL_PAGE_LRU;
 			goto out;
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 17335459d8dc..e8fd42be5fab 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -6176,7 +6176,7 @@ static int mem_cgroup_move_charge_pte_range(pmd_t *pmd,
 		target_type = get_mctgt_type_thp(vma, addr, *pmd, &target);
 		if (target_type == MC_TARGET_PAGE) {
 			page = target.page;
-			if (!isolate_lru_page(page)) {
+			if (isolate_lru_page(page)) {
 				if (!mem_cgroup_move_account(page, true,
 							     mc.from, mc.to)) {
 					mc.precharge -= HPAGE_PMD_NR;
@@ -6226,7 +6226,7 @@ static int mem_cgroup_move_charge_pte_range(pmd_t *pmd,
 			 */
 			if (PageTransCompound(page))
 				goto put;
-			if (!device && isolate_lru_page(page))
+			if (!device && !isolate_lru_page(page))
 				goto put;
 			if (!mem_cgroup_move_account(page, false,
 						mc.from, mc.to)) {
diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index db85c2d37f70..e504362fdb23 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -846,7 +846,7 @@ static const char * const action_page_types[] = {
  */
 static int delete_from_lru_cache(struct page *p)
 {
-	if (!isolate_lru_page(p)) {
+	if (isolate_lru_page(p)) {
 		/*
 		 * Clear sensible page flags, so that the buddy system won't
 		 * complain when the page is unpoison-and-freed.
@@ -2513,7 +2513,7 @@ static bool isolate_page(struct page *page, struct list_head *pagelist)
 		bool lru = !__PageMovable(page);
 
 		if (lru)
-			isolated = !isolate_lru_page(page);
+			isolated = isolate_lru_page(page);
 		else
 			isolated = !isolate_movable_page(page,
 							 ISOLATE_UNEVICTABLE);
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index a1e8c3e9ab08..17ed80707518 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1668,7 +1668,7 @@ do_migrate_range(unsigned long start_pfn, unsigned long end_pfn)
 		 * LRU and non-lru movable pages.
 		 */
 		if (PageLRU(page))
-			ret = isolate_lru_page(page);
+			ret = !isolate_lru_page(page);
 		else
 			ret = isolate_movable_page(page, ISOLATE_UNEVICTABLE);
 		if (!ret) { /* Success */
diff --git a/mm/migrate.c b/mm/migrate.c
index ef68a1aff35c..53010a142e7f 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -2132,11 +2132,14 @@ static int add_page_for_migration(struct mm_struct *mm, unsigned long addr,
 		}
 	} else {
 		struct page *head;
+		bool isolated;
 
 		head = compound_head(page);
-		err = isolate_lru_page(head);
-		if (err)
+		isolated = isolate_lru_page(head);
+		if (!isolated) {
+			err = -EBUSY;
 			goto out_putpage;
+		}
 
 		err = 1;
 		list_add_tail(&head->lru, pagelist);
@@ -2541,7 +2544,7 @@ static int numamigrate_isolate_page(pg_data_t *pgdat, struct page *page)
 		return 0;
 	}
 
-	if (isolate_lru_page(page))
+	if (!isolate_lru_page(page))
 		return 0;
 
 	mod_node_page_state(page_pgdat(page), NR_ISOLATED_ANON + page_is_file_lru(page),
diff --git a/mm/migrate_device.c b/mm/migrate_device.c
index 6c3740318a98..d30c9de60b0d 100644
--- a/mm/migrate_device.c
+++ b/mm/migrate_device.c
@@ -388,7 +388,7 @@ static unsigned long migrate_device_unmap(unsigned long *src_pfns,
 				allow_drain = false;
 			}
 
-			if (isolate_lru_page(page)) {
+			if (!isolate_lru_page(page)) {
 				src_pfns[i] &= ~MIGRATE_PFN_MIGRATE;
 				restore++;
 				continue;
-- 
2.27.0

On Tue, 14 Feb 2023 21:59:30 +0800 Baolin Wang <baolin.wang@linux.alibaba.com> wrote:

> The isolate_lru_page() can only return 0 or -EBUSY, and most users did
> not care about the negative error of isolate_lru_page(), except one user
> in add_page_for_migration(). So we can convert the isolate_lru_page() to
> return a boolean value, which can help to make the code more clear when
> checking the return value of isolate_lru_page().
> 
> Also convert all users' logic of checking the isolation state.
> 
> No functional changes intended.
> 
> Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
> ---
>  mm/folio-compat.c   | 12 +++---------
>  mm/internal.h       |  2 +-
>  mm/khugepaged.c     |  2 +-
>  mm/memcontrol.c     |  4 ++--
>  mm/memory-failure.c |  4 ++--
>  mm/memory_hotplug.c |  2 +-
>  mm/migrate.c        |  9 ++++++---
>  mm/migrate_device.c |  2 +-
>  8 files changed, 17 insertions(+), 20 deletions(-)
> 
[...]
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index a1e8c3e9ab08..17ed80707518 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -1668,7 +1668,7 @@ do_migrate_range(unsigned long start_pfn, unsigned long end_pfn)
>  		 * LRU and non-lru movable pages.
>  		 */
>  		if (PageLRU(page))
> -			ret = isolate_lru_page(page);
> +			ret = !isolate_lru_page(page);

This may change return value of this function.  That is, this function will
return 1 instead of -EBUSY after this change.  It's not a real issue as no
caller of this function takes care of the return value, though.


Thanks,
SJ

>  		else
>  			ret = isolate_movable_page(page, ISOLATE_UNEVICTABLE);
>  		if (!ret) { /* Success */
[...]

On 2/15/2023 3:32 AM, SeongJae Park wrote:
> On Tue, 14 Feb 2023 21:59:30 +0800 Baolin Wang <baolin.wang@linux.alibaba.com> wrote:
> 
>> The isolate_lru_page() can only return 0 or -EBUSY, and most users did
>> not care about the negative error of isolate_lru_page(), except one user
>> in add_page_for_migration(). So we can convert the isolate_lru_page() to
>> return a boolean value, which can help to make the code more clear when
>> checking the return value of isolate_lru_page().
>>
>> Also convert all users' logic of checking the isolation state.
>>
>> No functional changes intended.
>>
>> Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
>> ---
>>   mm/folio-compat.c   | 12 +++---------
>>   mm/internal.h       |  2 +-
>>   mm/khugepaged.c     |  2 +-
>>   mm/memcontrol.c     |  4 ++--
>>   mm/memory-failure.c |  4 ++--
>>   mm/memory_hotplug.c |  2 +-
>>   mm/migrate.c        |  9 ++++++---
>>   mm/migrate_device.c |  2 +-
>>   8 files changed, 17 insertions(+), 20 deletions(-)
>>
> [...]
>> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
>> index a1e8c3e9ab08..17ed80707518 100644
>> --- a/mm/memory_hotplug.c
>> +++ b/mm/memory_hotplug.c
>> @@ -1668,7 +1668,7 @@ do_migrate_range(unsigned long start_pfn, unsigned long end_pfn)
>>   		 * LRU and non-lru movable pages.
>>   		 */
>>   		if (PageLRU(page))
>> -			ret = isolate_lru_page(page);
>> +			ret = !isolate_lru_page(page);
> 
> This may change return value of this function.  That is, this function will
> return 1 instead of -EBUSY after this change.  It's not a real issue as no
> caller of this function takes care of the return value, though.

Yes, I've also thought about this. OK, I can keep the original logic 
here by adding a new variable. Thanks.

isolated = isolate_lru_page(page);
ret = isolated ? 0 : -EBUSY;