linux-kernel - [PATCH v2 11/14] gup: add FOLL_HINT_BULK, FAULT_FLAG

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Date:   Wed, 20 Oct 2021 10:03:02 -0700
From:   Ankur Arora <ankur.a.arora@...cle.com>
To:     linux-kernel@...r.kernel.org, linux-mm@...ck.org, x86@...nel.org
Cc:     mingo@...nel.org, bp@...en8.de, luto@...nel.org,
        akpm@...ux-foundation.org, mike.kravetz@...cle.com,
        jon.grimm@....com, kvm@...r.kernel.org, konrad.wilk@...cle.com,
        boris.ostrovsky@...cle.com, Ankur Arora <ankur.a.arora@...cle.com>
Subject: [PATCH v2 11/14] gup: add FOLL_HINT_BULK, FAULT_FLAG_UNCACHED

Add FOLL_HINT_BULK, which users of get_user_pages(), and
pin_user_pages() can use to signal that this call is one of
many allowing get_user_pages() to optimize accordingly.

Also add FAULT_FLAG_UNCACHED, which translates to the
same idea for the fault path.

As the second flag suggests, the intent for both is to hint the
use of an uncached path if one is available.

Signed-off-by: Ankur Arora <ankur.a.arora@...cle.com>
---
 include/linux/mm.h | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 3e8ddec2aba2..cf1c711fe5ba 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -446,6 +446,7 @@ extern pgprot_t protection_map[16];
  * @FAULT_FLAG_REMOTE: The fault is not for current task/mm.
  * @FAULT_FLAG_INSTRUCTION: The fault was during an instruction fetch.
  * @FAULT_FLAG_INTERRUPTIBLE: The fault can be interrupted by non-fatal signals.
+ * @FAULT_FLAG_UNCACHED: Fault handling to choose the uncached path.
  *
  * About @FAULT_FLAG_ALLOW_RETRY and @FAULT_FLAG_TRIED: we can specify
  * whether we would allow page faults to retry by specifying these two
@@ -477,6 +478,7 @@ enum fault_flag {
 	FAULT_FLAG_REMOTE =		1 << 7,
 	FAULT_FLAG_INSTRUCTION =	1 << 8,
 	FAULT_FLAG_INTERRUPTIBLE =	1 << 9,
+	FAULT_FLAG_UNCACHED =		1 << 10,
 };
 
 /*
@@ -2864,6 +2866,7 @@ struct page *follow_page(struct vm_area_struct *vma, unsigned long address,
 #define FOLL_SPLIT_PMD	0x20000	/* split huge pmd before returning */
 #define FOLL_PIN	0x40000	/* pages must be released via unpin_user_page */
 #define FOLL_FAST_ONLY	0x80000	/* gup_fast: prevent fall-back to slow gup */
+#define FOLL_HINT_BULK	0x100000 /* part of a larger extent being gup'd */
 
 /*
  * FOLL_PIN and FOLL_LONGTERM may be used in various combinations with each
-- 
2.29.2