linux-kernel - [PATCH v3 18/21] gup: add FOLL_HINT_BULK, FAULT_FLAG_NON

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Date:   Mon,  6 Jun 2022 20:37:22 +0000
From:   Ankur Arora <ankur.a.arora@...cle.com>
To:     linux-kernel@...r.kernel.org, linux-mm@...ck.org, x86@...nel.org
Cc:     torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
        mike.kravetz@...cle.com, mingo@...nel.org, luto@...nel.org,
        tglx@...utronix.de, bp@...en8.de, peterz@...radead.org,
        ak@...ux.intel.com, arnd@...db.de, jgg@...dia.com,
        jon.grimm@....com, boris.ostrovsky@...cle.com,
        konrad.wilk@...cle.com, joao.m.martins@...cle.com,
        ankur.a.arora@...cle.com
Subject: [PATCH v3 18/21] gup: add FOLL_HINT_BULK, FAULT_FLAG_NON_CACHING

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

Additionally, add FAULT_FLAG_NON_CACHING, which in the fault handling
path signals that the underlying logic can use non-caching primitives.
This is a possible optimization for FOLL_HINT_BULK calls.

Signed-off-by: Ankur Arora <ankur.a.arora@...cle.com>
---
 include/linux/mm.h       | 1 +
 include/linux/mm_types.h | 2 ++
 2 files changed, 3 insertions(+)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index a9b0c1889348..dbd8b7344dfc 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2941,6 +2941,7 @@ 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
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index b34ff2cdbc4f..287b3018c14d 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -824,6 +824,7 @@ typedef struct {
  *                      mapped R/O.
  * @FAULT_FLAG_ORIG_PTE_VALID: whether the fault has vmf->orig_pte cached.
  *                        We should only access orig_pte if this flag set.
+ * @FAULT_FLAG_NON_CACHING: Avoid polluting the cache if possible.
  *
  * About @FAULT_FLAG_ALLOW_RETRY and @FAULT_FLAG_TRIED: we can specify
  * whether we would allow page faults to retry by specifying these two
@@ -861,6 +862,7 @@ enum fault_flag {
 	FAULT_FLAG_INTERRUPTIBLE =	1 << 9,
 	FAULT_FLAG_UNSHARE =		1 << 10,
 	FAULT_FLAG_ORIG_PTE_VALID =	1 << 11,
+	FAULT_FLAG_NON_CACHING =	1 << 12,
 };
 
 typedef unsigned int __bitwise zap_flags_t;
-- 
2.31.1