+ memcg-v1-no-need-for-memcg-locking-for-writeback-tracking.patch added to mm-unstable branch

+ memcg-v1-no-need-for-memcg-locking-for-writeback-tracking.patch added to mm-unstable branch

[Andrew Morton]

The patch titled
     Subject: memcg-v1: no need for memcg locking for writeback tracking
has been added to the -mm mm-unstable branch.  Its filename is
     memcg-v1-no-need-for-memcg-locking-for-writeback-tracking.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/memcg-v1-no-need-for-memcg-locking-for-writeback-tracking.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: Shakeel Butt <shakeel.butt@linux.dev>
Subject: memcg-v1: no need for memcg locking for writeback tracking
Date: Thu, 24 Oct 2024 18:23:01 -0700

During the era of memcg charge migration, the kernel has to be make
sure that the writeback stat updates do not race with the charge
migration.  Otherwise it might update the writeback stats of the wrong
memcg.  Now with the memcg charge migration gone, there is no more race
for writeback stat updates and the previous locking can be removed.

Link: https://lkml.kernel.org/r/20241025012304.2473312-5-shakeel.butt@linux.dev
Signed-off-by: Shakeel Butt <shakeel.butt@linux.dev>
Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/page-writeback.c |    4 ----
 1 file changed, 4 deletions(-)

--- a/mm/page-writeback.c~memcg-v1-no-need-for-memcg-locking-for-writeback-tracking
+++ a/mm/page-writeback.c
@@ -3083,7 +3083,6 @@ bool __folio_end_writeback(struct folio
 	struct address_space *mapping = folio_mapping(folio);
 	bool ret;
 
-	folio_memcg_lock(folio);
 	if (mapping && mapping_use_writeback_tags(mapping)) {
 		struct inode *inode = mapping->host;
 		struct backing_dev_info *bdi = inode_to_bdi(inode);
@@ -3114,7 +3113,6 @@ bool __folio_end_writeback(struct folio
 	lruvec_stat_mod_folio(folio, NR_WRITEBACK, -nr);
 	zone_stat_mod_folio(folio, NR_ZONE_WRITE_PENDING, -nr);
 	node_stat_mod_folio(folio, NR_WRITTEN, nr);
-	folio_memcg_unlock(folio);
 
 	return ret;
 }
@@ -3127,7 +3125,6 @@ void __folio_start_writeback(struct foli
 
 	VM_BUG_ON_FOLIO(folio_test_writeback(folio), folio);
 
-	folio_memcg_lock(folio);
 	if (mapping && mapping_use_writeback_tags(mapping)) {
 		XA_STATE(xas, &mapping->i_pages, folio_index(folio));
 		struct inode *inode = mapping->host;
@@ -3168,7 +3165,6 @@ void __folio_start_writeback(struct foli
 
 	lruvec_stat_mod_folio(folio, NR_WRITEBACK, nr);
 	zone_stat_mod_folio(folio, NR_ZONE_WRITE_PENDING, nr);
-	folio_memcg_unlock(folio);
 
 	access_ret = arch_make_folio_accessible(folio);
 	/*
_

Patches currently in -mm which might be from shakeel.butt@linux.dev are

mm-optimize-truncation-of-shadow-entries.patch
mm-optimize-invalidation-of-shadow-entries.patch
mm-truncate-reset-xa_has_values-flag-on-each-iteration.patch
memcg-add-tracing-for-memcg-stat-updates.patch
memcg-add-tracing-for-memcg-stat-updates-v2.patch
memcg-v1-fully-deprecate-move_charge_at_immigrate.patch
memcg-v1-remove-charge-move-code.patch
memcg-v1-no-need-for-memcg-locking-for-dirty-tracking.patch
memcg-v1-no-need-for-memcg-locking-for-writeback-tracking.patch
memcg-v1-no-need-for-memcg-locking-for-mglru.patch
memcg-v1-remove-memcg-move-locking-code.patch