+ mm-hugetlb-avoid-calculating-fault_mutex_hash-in-truncate_op-case.patch added to -mm tree

+ mm-hugetlb-avoid-calculating-fault_mutex_hash-in-truncate_op-case.patch added to -mm tree

[akpm]

The patch titled
     Subject: mm/hugetlb: avoid calculating fault_mutex_hash in truncate_op case
has been added to the -mm tree.  Its filename is
     mm-hugetlb-avoid-calculating-fault_mutex_hash-in-truncate_op-case.patch

This patch should soon appear at
    https://ozlabs.org/~akpm/mmots/broken-out/mm-hugetlb-avoid-calculating-fault_mutex_hash-in-truncate_op-case.patch
and later at
    https://ozlabs.org/~akpm/mmotm/broken-out/mm-hugetlb-avoid-calculating-fault_mutex_hash-in-truncate_op-case.patch

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------------------------------------------------------
From: Miaohe Lin <linmiaohe@huawei.com>
Subject: mm/hugetlb: avoid calculating fault_mutex_hash in truncate_op case

The fault_mutex hashing overhead can be avoided in truncate_op case
because page faults can not race with truncation in this routine.  So
calculate hash for fault_mutex only in !truncate_op case to save some cpu
cycles.

Link: https://lkml.kernel.org/r/20210308112809.26107-6-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 fs/hugetlbfs/inode.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/fs/hugetlbfs/inode.c~mm-hugetlb-avoid-calculating-fault_mutex_hash-in-truncate_op-case
+++ a/fs/hugetlbfs/inode.c
@@ -482,10 +482,9 @@ static void remove_inode_hugepages(struc
 
 		for (i = 0; i < pagevec_count(&pvec); ++i) {
 			struct page *page = pvec.pages[i];
-			u32 hash;
+			u32 hash = 0;
 
 			index = page->index;
-			hash = hugetlb_fault_mutex_hash(mapping, index);
 			if (!truncate_op) {
 				/*
 				 * Only need to hold the fault mutex in the
@@ -493,6 +492,7 @@ static void remove_inode_hugepages(struc
 				 * page faults.  Races are not possible in the
 				 * case of truncation.
 				 */
+				hash = hugetlb_fault_mutex_hash(mapping, index);
 				mutex_lock(&hugetlb_fault_mutex_table[hash]);
 			}
 
_

Patches currently in -mm which might be from linmiaohe@huawei.com are

hugetlb_cgroup-fix-imbalanced-css_get-and-css_put-pair-for-shared-mappings.patch
mm-hugetlb-remove-redundant-reservation-check-condition-in-alloc_huge_page.patch
mm-hugetlb-use-some-helper-functions-to-cleanup-code.patch
mm-hugetlb-optimize-the-surplus-state-transfer-code-in-move_hugetlb_state.patch
hugetlb_cgroup-remove-unnecessary-vm_bug_on_page-in-hugetlb_cgroup_migrate.patch
mm-hugetlb-simplify-the-code-when-alloc_huge_page-failed-in-hugetlb_no_page.patch
mm-hugetlb-avoid-calculating-fault_mutex_hash-in-truncate_op-case.patch