[v4,32/32] mm/slob: Remove unnecessary page_mapcount_reset() function call

Commit Message

Vlastimil Babka Jan. 4, 2022, 12:10 a.m. UTC

From: Hyeonggon Yoo <[e-mail]>

After commit f2452d14cdb3 ("mm/sl*b: Differentiate struct slab fields by
sl*b implementations"), we can reorder fields of struct slab depending
on slab allocator.

For now, page_mapcount_reset() is called because page->_mapcount and
slab->units have same offset. But this is not necessary for struct slab.
Use unused field for units instead.

Signed-off-by: Hyeonggon Yoo <[e-mail]>
Signed-off-by: Vlastimil Babka <[e-mail]>
Link: https://lore.kernel.org/r/20211212065241.GA886691@odroid
---
 mm/slab.h | 4 ++--
 mm/slob.c | 1 -
 2 files changed, 2 insertions(+), 3 deletions(-)

Patch

diff --git a/mm/slab.h b/mm/slab.h
index ac8be7dab535..e10d0d4c9bfa 100644
--- a/mm/slab.h
+++ b/mm/slab.h
@@ -50,8 +50,8 @@  struct slab {
 	struct list_head slab_list;
 	void *__unused_1;
 	void *freelist;		/* first free block */
-	void *__unused_2;
-	int units;
+	long units;
+	unsigned int __unused_2;
 
 #else
 #error "Unexpected slab allocator configured"
diff --git a/mm/slob.c b/mm/slob.c
index 3c6cadbbc238..60c5842215f1 100644
--- a/mm/slob.c
+++ b/mm/slob.c
@@ -404,7 +404,6 @@  static void slob_free(void *block, int size)
 			clear_slob_page_free(sp);
 		spin_unlock_irqrestore(&slob_lock, flags);
 		__folio_clear_slab(slab_folio(sp));
-		page_mapcount_reset(slab_page(sp));
 		slob_free_pages(b, 0);
 		return;
 	}