From c6715787cc2e683af3fb220fe7b3be8193a043bb Mon Sep 17 00:00:00 2001
From: Hugh Dickins <hughd@google.com>
Date: Thu, 2 Sep 2021 14:54:24 -0700
Subject: [PATCH] huge tmpfs: remove shrinklist addition from shmem_setattr()

References: git fixes (mm/shmem)
Patch-mainline: v5.15-rc1
Git-commit: 2b5bbcb1c9c2cd05a06dcf54df77255a8c406a7b

There's a block of code in shmem_setattr() to add the inode to
shmem_unused_huge_shrink()'s shrinklist when lowering i_size: it dates
from before 5.7 changed truncation to do split_huge_page() for itself, and
should have been removed at that time.

I am over-stating that: split_huge_page() can fail (notably if there's an
extra reference to the page at that time), so there might be value in
retrying.  But there were already retries as truncation worked through the
tails, and this addition risks repeating unsuccessful retries
indefinitely: I'd rather remove it now, and work on reducing the chance of
split_huge_page() failures separately, if we need to.

Link: https://lkml.kernel.org/r/b73b3492-8822-18f9-83e2-938528cdde94@google.com
Fixes: 71725ed10c40 ("mm: huge tmpfs: try to split_huge_page() when punching hole")
Signed-off-by: Hugh Dickins <hughd@google.com>
Reviewed-by: Yang Shi <shy828301@gmail.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Shakeel Butt <shakeelb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Mel Gorman <mgorman@suse.de>
---
 mm/shmem.c | 19 -------------------
 1 file changed, 19 deletions(-)

diff --git a/mm/shmem.c b/mm/shmem.c
index e391325dfc21..9403048f4ee1 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1058,7 +1058,6 @@ static int shmem_setattr(struct user_namespace *mnt_userns,
 {
 	struct inode *inode = d_inode(dentry);
 	struct shmem_inode_info *info = SHMEM_I(inode);
-	struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
 	int error;
 
 	error = setattr_prepare(&init_user_ns, dentry, attr);
@@ -1094,24 +1093,6 @@ static int shmem_setattr(struct user_namespace *mnt_userns,
 			if (oldsize > holebegin)
 				unmap_mapping_range(inode->i_mapping,
 							holebegin, 0, 1);
-
-			/*
-			 * Part of the huge page can be beyond i_size: subject
-			 * to shrink under memory pressure.
-			 */
-			if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) {
-				spin_lock(&sbinfo->shrinklist_lock);
-				/*
-				 * _careful to defend against unlocked access to
-				 * ->shrink_list in shmem_unused_huge_shrink()
-				 */
-				if (list_empty_careful(&info->shrinklist)) {
-					list_add_tail(&info->shrinklist,
-							&sbinfo->shrinklist);
-					sbinfo->shrinklist_len++;
-				}
-				spin_unlock(&sbinfo->shrinklist_lock);
-			}
 		}
 	}