linux-kernel - Re: [PATCH v6 12/12] mmap locking API: convert mmap

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Date:   Wed, 20 May 2020 20:22:42 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Michel Lespinasse <walken@...gle.com>
Cc:     linux-mm <linux-mm@...ck.org>, LKML <linux-kernel@...r.kernel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Laurent Dufour <ldufour@...ux.ibm.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Matthew Wilcox <willy@...radead.org>,
        Liam Howlett <Liam.Howlett@...cle.com>,
        Jerome Glisse <jglisse@...hat.com>,
        Davidlohr Bueso <dave@...olabs.net>,
        David Rientjes <rientjes@...gle.com>,
        Hugh Dickins <hughd@...gle.com>, Ying Han <yinghan@...gle.com>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Daniel Jordan <daniel.m.jordan@...cle.com>,
        John Hubbard <jhubbard@...dia.com>
Subject: Re: [PATCH v6 12/12] mmap locking API: convert mmap_sem comments

On Tue, 19 May 2020 22:29:08 -0700 Michel Lespinasse <walken@...gle.com> wrote:

> Convert comments that reference mmap_sem to reference mmap_lock instead.

This may not be complete..

From: Andrew Morton <akpm@...ux-foundation.org>
Subject: mmap-locking-api-convert-mmap_sem-comments-fix

fix up linux-next leftovers

Cc: Daniel Jordan <daniel.m.jordan@...cle.com>
Cc: Davidlohr Bueso <dbueso@...e.de>
Cc: David Rientjes <rientjes@...gle.com>
Cc: Hugh Dickins <hughd@...gle.com>
Cc: Jason Gunthorpe <jgg@...pe.ca>
Cc: Jerome Glisse <jglisse@...hat.com>
Cc: John Hubbard <jhubbard@...dia.com>
Cc: Laurent Dufour <ldufour@...ux.ibm.com>
Cc: Liam Howlett <Liam.Howlett@...cle.com>
Cc: Matthew Wilcox <willy@...radead.org>
Cc: Michel Lespinasse <walken@...gle.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Vlastimil Babka <vbabka@...e.cz>
Cc: Ying Han <yinghan@...gle.com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
---

 arch/powerpc/mm/fault.c |    2 +-
 include/linux/pgtable.h |    6 +++---
 2 files changed, 4 insertions(+), 4 deletions(-)

--- a/arch/powerpc/mm/fault.c~mmap-locking-api-convert-mmap_sem-comments-fix
+++ a/arch/powerpc/mm/fault.c
@@ -138,7 +138,7 @@ static noinline int bad_access_pkey(stru
 	 * 2. T1   : set AMR to deny access to pkey=4, touches, page
 	 * 3. T1   : faults...
 	 * 4.    T2: mprotect_key(foo, PAGE_SIZE, pkey=5);
-	 * 5. T1   : enters fault handler, takes mmap_sem, etc...
+	 * 5. T1   : enters fault handler, takes mmap_lock, etc...
 	 * 6. T1   : reaches here, sees vma_pkey(vma)=5, when we really
 	 *	     faulted on a pte with its pkey=4.
 	 */
--- a/include/linux/pgtable.h~mmap-locking-api-convert-mmap_sem-comments-fix
+++ a/include/linux/pgtable.h
@@ -1101,11 +1101,11 @@ static inline pmd_t pmd_read_atomic(pmd_
 #endif
 /*
  * This function is meant to be used by sites walking pagetables with
- * the mmap_sem hold in read mode to protect against MADV_DONTNEED and
+ * the mmap_lock held in read mode to protect against MADV_DONTNEED and
  * transhuge page faults. MADV_DONTNEED can convert a transhuge pmd
  * into a null pmd and the transhuge page fault can convert a null pmd
  * into an hugepmd or into a regular pmd (if the hugepage allocation
- * fails). While holding the mmap_sem in read mode the pmd becomes
+ * fails). While holding the mmap_lock in read mode the pmd becomes
  * stable and stops changing under us only if it's not null and not a
  * transhuge pmd. When those races occurs and this function makes a
  * difference vs the standard pmd_none_or_clear_bad, the result is
@@ -1115,7 +1115,7 @@ static inline pmd_t pmd_read_atomic(pmd_
  *
  * For 32bit kernels with a 64bit large pmd_t this automatically takes
  * care of reading the pmd atomically to avoid SMP race conditions
- * against pmd_populate() when the mmap_sem is hold for reading by the
+ * against pmd_populate() when the mmap_lock is hold for reading by the
  * caller (a special atomic read not done by "gcc" as in the generic
  * version above, is also needed when THP is disabled because the page
  * fault can populate the pmd from under us).
_