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From:   Feng Tang <feng.tang@intel.com>
To:     Andrew Morton <akpm@linux-foundation.org>,
        Michal Hocko <mhocko@suse.com>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Matthew Wilcox <willy@infradead.org>,
        Mel Gorman <mgorman@suse.de>,
        Kees Cook <keescook@chromium.org>, Qian Cai <cai@lca.pw>,
        andi.kleen@intel.com, tim.c.chen@intel.com, dave.hansen@intel.com,
        ying.huang@intel.com, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org
Cc:     Feng Tang <feng.tang@intel.com>,
        Konstantin Khlebnikov <koct9i@gmail.com>
Subject: [PATCH v4 3/4] mm/util.c: remove the VM_WARN_ONCE for vm_committed_as underflow check
Date:   Fri, 29 May 2020 09:06:09 +0800
Message-Id: <1590714370-67182-4-git-send-email-feng.tang@intel.com>
In-Reply-To: <1590714370-67182-1-git-send-email-feng.tang@intel.com>
References: <1590714370-67182-1-git-send-email-feng.tang@intel.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

As is explained by Michal Hocko:

: Looking at the history, this has been added by 82f71ae4a2b8
: ("mm: catch memory commitment underflow") to have a safety check
: for issues which have been fixed. There doesn't seem to be any bug
: reports mentioning this splat since then so it is likely just
: spending cycles for a hot path (yes many people run with DEBUG_VM)
: without a strong reason.

Signed-off-by: Feng Tang <feng.tang@intel.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Qian Cai <cai@lca.pw>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Andi Kleen <andi.kleen@intel.com>
---
 mm/util.c | 8 --------
 1 file changed, 8 deletions(-)

diff --git a/mm/util.c b/mm/util.c
index 3c7a08c..fe63271 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -814,14 +814,6 @@ int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin)
 {
 	long allowed;
 
-	/*
-	 * A transient decrease in the value is unlikely, so no need
-	 * READ_ONCE() for vm_committed_as.count.
-	 */
-	VM_WARN_ONCE(data_race(percpu_counter_read(&vm_committed_as) <
-			-(s64)vm_committed_as_batch * num_online_cpus()),
-			"memory commitment underflow");
-
 	vm_acct_memory(pages);
 
 	/*
-- 
2.7.4