linux-kernel - [PATCH 03/16] huge tmpfs: remove shrinklist addition from shmem

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Date:   Fri, 30 Jul 2021 00:30:56 -0700 (PDT)
From:   Hugh Dickins <hughd@...gle.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
cc:     Hugh Dickins <hughd@...gle.com>,
        Shakeel Butt <shakeelb@...gle.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Yang Shi <shy828301@...il.com>,
        Miaohe Lin <linmiaohe@...wei.com>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Michal Hocko <mhocko@...e.com>,
        Rik van Riel <riel@...riel.com>,
        Christoph Hellwig <hch@...radead.org>,
        Matthew Wilcox <willy@...radead.org>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        Alexey Gladkov <legion@...nel.org>,
        Chris Wilson <chris@...is-wilson.co.uk>,
        Matthew Auld <matthew.auld@...el.com>,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-api@...r.kernel.org, linux-mm@...ck.org
Subject: [PATCH 03/16] huge tmpfs: remove shrinklist addition from
 shmem_setattr()

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.

Fixes: 71725ed10c40 ("mm: huge tmpfs: try to split_huge_page() when punching hole")
Signed-off-by: Hugh Dickins <hughd@...gle.com>
---
 mm/shmem.c | 19 -------------------
 1 file changed, 19 deletions(-)

diff --git a/mm/shmem.c b/mm/shmem.c
index 24c9da6b41c2..ce3ccaac54d6 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1061,7 +1061,6 @@ 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);
@@ -1097,24 +1096,6 @@ 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);
-			}
 		}
 	}
 
-- 
2.26.2