The patch titled
Subject: mm: change to return bool for folio_isolate_lru()
has been added to the -mm mm-unstable branch. Its filename is
mm-change-to-return-bool-for-folio_isolate_lru.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-change-to-return-bool-for-folio_isolate_lru.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>
Subject: mm: change to return bool for folio_isolate_lru()
Date: Wed, 15 Feb 2023 18:39:34 +0800
Patch series "Change the return value for page isolation functions", v3.
Now the page isolation functions did not return a boolean to indicate
success or not, instead it will return a negative error when failed
to isolate a page. So below code used in most places seem a boolean
success/failure thing, which can confuse people whether the isolation
is successful.
if (folio_isolate_lru(folio))
continue;
Moreover the page isolation functions only return 0 or -EBUSY, and
most users did not care about the negative error except for few users,
thus we can convert all page isolation functions to return a boolean
value, which can remove the confusion to make code more clear.
No functional changes intended in this patch series.
This patch (of 4):
Now the folio_isolate_lru() did not return a boolean value to indicate
isolation success or not, however below code checking the return value can
make people think that it was a boolean success/failure thing, which makes
people easy to make mistakes (see the fix patch[1]).
if (folio_isolate_lru(folio))
continue;
Thus it's better to check the negative error value expilictly returned by
folio_isolate_lru(), which makes code more clear per Linus's
suggestion[2]. Moreover Matthew suggested we can convert the isolation
functions to return a boolean[3], since most users did not care about the
negative error value, and can also remove the confusing of checking return
value.
So this patch converts the folio_isolate_lru() to return a boolean value,
which means return 'true' to indicate the folio isolation is successful,
and 'false' means a failure to isolation. Meanwhile changing all users'
logic of checking the isolation state.
No functional changes intended.
[1] https://lore.kernel.org/all/20230131063206.28820-1-Kuan-Ying.Lee@xxxxxxxxxxxx/T/#u
[2] https://lore.kernel.org/all/CAHk-=wiBrY+O-4=2mrbVyxR+hOqfdJ=Do6xoucfJ9_5az01L4Q@xxxxxxxxxxxxxx/
[3] https://lore.kernel.org/all/Y+sTFqwMNAjDvxw3@xxxxxxxxxxxxxxxxxxxx/
Link: https://lkml.kernel.org/r/cover.1676424378.git.baolin.wang@xxxxxxxxxxxxxxxxx
Link: https://lkml.kernel.org/r/8a4e3679ed4196168efadf7ea36c038f2f7d5aa9.1676424378.git.baolin.wang@xxxxxxxxxxxxxxxxx
Signed-off-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>
Reviewed-by: SeongJae Park <sj@xxxxxxxxxx>
Acked-by: David Hildenbrand <david@xxxxxxxxxx>
Reviewed-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Acked-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Miaohe Lin <linmiaohe@xxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxxxx>
Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Cc: Muchun Song <muchun.song@xxxxxxxxx>
Cc: Naoya Horiguchi <naoya.horiguchi@xxxxxxx>
Cc: Oscar Salvador <osalvador@xxxxxxx>
Cc: Roman Gushchin <roman.gushchin@xxxxxxxxx>
Cc: Shakeel Butt <shakeelb@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/damon/paddr.c | 2 +-
mm/folio-compat.c | 8 +++++++-
mm/gup.c | 2 +-
mm/internal.h | 2 +-
mm/khugepaged.c | 2 +-
mm/madvise.c | 4 ++--
mm/mempolicy.c | 2 +-
mm/vmscan.c | 10 +++++-----
8 files changed, 19 insertions(+), 13 deletions(-)
--- a/mm/damon/paddr.c~mm-change-to-return-bool-for-folio_isolate_lru
+++ a/mm/damon/paddr.c
@@ -246,7 +246,7 @@ static unsigned long damon_pa_pageout(st
folio_clear_referenced(folio);
folio_test_clear_young(folio);
- if (folio_isolate_lru(folio)) {
+ if (!folio_isolate_lru(folio)) {
folio_put(folio);
continue;
}
--- a/mm/folio-compat.c~mm-change-to-return-bool-for-folio_isolate_lru
+++ a/mm/folio-compat.c
@@ -115,9 +115,15 @@ EXPORT_SYMBOL(grab_cache_page_write_begi
int isolate_lru_page(struct page *page)
{
+ bool ret;
+
if (WARN_RATELIMIT(PageTail(page), "trying to isolate tail page"))
return -EBUSY;
- return folio_isolate_lru((struct folio *)page);
+ ret = folio_isolate_lru((struct folio *)page);
+ if (ret)
+ return 0;
+
+ return -EBUSY;
}
void putback_lru_page(struct page *page)
--- a/mm/gup.c~mm-change-to-return-bool-for-folio_isolate_lru
+++ a/mm/gup.c
@@ -1939,7 +1939,7 @@ static unsigned long collect_longterm_un
drain_allow = false;
}
- if (folio_isolate_lru(folio))
+ if (!folio_isolate_lru(folio))
continue;
list_add_tail(&folio->lru, movable_page_list);
--- a/mm/internal.h~mm-change-to-return-bool-for-folio_isolate_lru
+++ a/mm/internal.h
@@ -188,7 +188,7 @@ pgprot_t __init early_memremap_pgprot_ad
* in mm/vmscan.c:
*/
int isolate_lru_page(struct page *page);
-int folio_isolate_lru(struct folio *folio);
+bool folio_isolate_lru(struct folio *folio);
void putback_lru_page(struct page *page);
void folio_putback_lru(struct folio *folio);
extern void reclaim_throttle(pg_data_t *pgdat, enum vmscan_throttle_state reason);
--- a/mm/khugepaged.c~mm-change-to-return-bool-for-folio_isolate_lru
+++ a/mm/khugepaged.c
@@ -2047,7 +2047,7 @@ static int collapse_file(struct mm_struc
goto out_unlock;
}
- if (folio_isolate_lru(folio)) {
+ if (!folio_isolate_lru(folio)) {
result = SCAN_DEL_PAGE_LRU;
goto out_unlock;
}
--- a/mm/madvise.c~mm-change-to-return-bool-for-folio_isolate_lru
+++ a/mm/madvise.c
@@ -406,7 +406,7 @@ static int madvise_cold_or_pageout_pte_r
folio_clear_referenced(folio);
folio_test_clear_young(folio);
if (pageout) {
- if (!folio_isolate_lru(folio)) {
+ if (folio_isolate_lru(folio)) {
if (folio_test_unevictable(folio))
folio_putback_lru(folio);
else
@@ -500,7 +500,7 @@ regular_folio:
folio_clear_referenced(folio);
folio_test_clear_young(folio);
if (pageout) {
- if (!folio_isolate_lru(folio)) {
+ if (folio_isolate_lru(folio)) {
if (folio_test_unevictable(folio))
folio_putback_lru(folio);
else
--- a/mm/mempolicy.c~mm-change-to-return-bool-for-folio_isolate_lru
+++ a/mm/mempolicy.c
@@ -1033,7 +1033,7 @@ static int migrate_folio_add(struct foli
* expensive, so check the estimated mapcount of the folio instead.
*/
if ((flags & MPOL_MF_MOVE_ALL) || folio_estimated_sharers(folio) == 1) {
- if (!folio_isolate_lru(folio)) {
+ if (folio_isolate_lru(folio)) {
list_add_tail(&folio->lru, foliolist);
node_stat_mod_folio(folio,
NR_ISOLATED_ANON + folio_is_file_lru(folio),
--- a/mm/vmscan.c~mm-change-to-return-bool-for-folio_isolate_lru
+++ a/mm/vmscan.c
@@ -2337,12 +2337,12 @@ move:
* (2) The lru_lock must not be held.
* (3) Interrupts must be enabled.
*
- * Return: 0 if the folio was removed from an LRU list.
- * -EBUSY if the folio was not on an LRU list.
+ * Return: true if the folio was removed from an LRU list.
+ * false if the folio was not on an LRU list.
*/
-int folio_isolate_lru(struct folio *folio)
+bool folio_isolate_lru(struct folio *folio)
{
- int ret = -EBUSY;
+ bool ret = false;
VM_BUG_ON_FOLIO(!folio_ref_count(folio), folio);
@@ -2353,7 +2353,7 @@ int folio_isolate_lru(struct folio *foli
lruvec = folio_lruvec_lock_irq(folio);
lruvec_del_folio(lruvec, folio);
unlock_page_lruvec_irq(lruvec);
- ret = 0;
+ ret = true;
}
return ret;
_
Patches currently in -mm which might be from baolin.wang@xxxxxxxxxxxxxxxxx are
mm-change-to-return-bool-for-folio_isolate_lru.patch
mm-change-to-return-bool-for-isolate_lru_page.patch
mm-hugetlb-change-to-return-bool-for-isolate_hugetlb.patch
mm-change-to-return-bool-for-isolate_movable_page.patch
