The patch titled
Subject: mm/mremap_pages: save a few cycles in get_dev_pagemap()
has been added to the -mm mm-unstable branch. Its filename is
mm-mremap_pages-save-a-few-cycles-in-get_dev_pagemap.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-mremap_pages-save-a-few-cycles-in-get_dev_pagemap.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next via the mm-everything
branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there every 2-3 working days
------------------------------------------------------
From: Christophe JAILLET <christophe.jaillet@xxxxxxxxxx>
Subject: mm/mremap_pages: save a few cycles in get_dev_pagemap()
Date: Fri, 2 Sep 2022 18:39:52 +0200
Use 'percpu_ref_tryget_live_rcu()' instead of 'percpu_ref_tryget_live()'
to save a few cycles when it is known that the rcu lock is already
taken/released.
Link: https://lkml.kernel.org/r/9ef1562a1975371360f3e263856e9f1c5749b656.1662136782.git.christophe.jaillet@xxxxxxxxxx
Signed-off-by: Christophe JAILLET <christophe.jaillet@xxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/memremap.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/mm/memremap.c~mm-mremap_pages-save-a-few-cycles-in-get_dev_pagemap
+++ a/mm/memremap.c
@@ -454,7 +454,7 @@ struct dev_pagemap *get_dev_pagemap(unsi
/* fall back to slow path lookup */
rcu_read_lock();
pgmap = xa_load(&pgmap_array, PHYS_PFN(phys));
- if (pgmap && !percpu_ref_tryget_live(&pgmap->ref))
+ if (pgmap && !percpu_ref_tryget_live_rcu(&pgmap->ref))
pgmap = NULL;
rcu_read_unlock();
_
Patches currently in -mm which might be from christophe.jaillet@xxxxxxxxxx are
mm-mremap_pages-save-a-few-cycles-in-get_dev_pagemap.patch
