linux-kernel - [PATCH v1] mm/gup: adjust stale comment for RCU GUP-fast

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Message-Id: <20220901072119.37588-1-david@redhat.com>
Date:   Thu,  1 Sep 2022 09:21:19 +0200
From:   David Hildenbrand <david@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     linux-mm@...ck.org, David Hildenbrand <david@...hat.com>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Sasha Levin <sasha.levin@...cle.com>,
        "Aneesh Kumar K . V" <aneesh.kumar@...ux.vnet.ibm.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Jerome Marchand <jmarchan@...hat.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Hugh Dickins <hughd@...gle.com>,
        Jason Gunthorpe <jgg@...dia.com>,
        John Hubbard <jhubbard@...dia.com>,
        Peter Xu <peterx@...hat.com>, Yang Shi <shy828301@...il.com>
Subject: [PATCH v1] mm/gup: adjust stale comment for RCU GUP-fast

commit 4b471e8898c3 ("mm, thp: remove infrastructure for handling splitting
PMDs") didn't remove all details about the THP split requirements for
RCU GUP-fast.

IPI broeadcasts on THP split are no longer required.

Cc: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
Cc: Sasha Levin <sasha.levin@...cle.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@...ux.vnet.ibm.com>
Cc: Vlastimil Babka <vbabka@...e.cz>
Cc: Jerome Marchand <jmarchan@...hat.com>
Cc: Andrea Arcangeli <aarcange@...hat.com>
Cc: Hugh Dickins <hughd@...gle.com>
Cc: Jason Gunthorpe <jgg@...dia.com>
Cc: John Hubbard <jhubbard@...dia.com>
Cc: Peter Xu <peterx@...hat.com>
Cc: Yang Shi <shy828301@...il.com>
Signed-off-by: David Hildenbrand <david@...hat.com>
---
 mm/gup.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/mm/gup.c b/mm/gup.c
index 5abdaf487460..cfe71f422787 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -2309,9 +2309,8 @@ EXPORT_SYMBOL(get_user_pages_unlocked);
  *
  * Another way to achieve this is to batch up page table containing pages
  * belonging to more than one mm_user, then rcu_sched a callback to free those
- * pages. Disabling interrupts will allow the fast_gup walker to both block
- * the rcu_sched callback, and an IPI that we broadcast for splitting THPs
- * (which is a relatively rare event). The code below adopts this strategy.
+ * pages. Disabling interrupts will allow the fast_gup walker to block the
+ * rcu_sched callback.
  *
  * Before activating this code, please be aware that the following assumptions
  * are currently made:
-- 
2.37.1