linux-kernel - [PATCH v2 08/35] mm: add FAULT_FLAG

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Date:   Fri, 28 Jan 2022 05:09:39 -0800
From:   Michel Lespinasse <michel@...pinasse.org>
To:     Linux-MM <linux-mm@...ck.org>, linux-kernel@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     kernel-team@...com, Laurent Dufour <ldufour@...ux.ibm.com>,
        Jerome Glisse <jglisse@...gle.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Michal Hocko <mhocko@...e.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Davidlohr Bueso <dave@...olabs.net>,
        Matthew Wilcox <willy@...radead.org>,
        Liam Howlett <liam.howlett@...cle.com>,
        Rik van Riel <riel@...riel.com>,
        Paul McKenney <paulmck@...nel.org>,
        Song Liu <songliubraving@...com>,
        Suren Baghdasaryan <surenb@...gle.com>,
        Minchan Kim <minchan@...gle.com>,
        Joel Fernandes <joelaf@...gle.com>,
        David Rientjes <rientjes@...gle.com>,
        Axel Rasmussen <axelrasmussen@...gle.com>,
        Andy Lutomirski <luto@...nel.org>,
        Michel Lespinasse <michel@...pinasse.org>
Subject: [PATCH v2 08/35] mm: add FAULT_FLAG_SPECULATIVE flag

Define the new FAULT_FLAG_SPECULATIVE flag, which indicates when we are
attempting speculative fault handling (without holding the mmap lock).

Signed-off-by: Michel Lespinasse <michel@...pinasse.org>
---
 include/linux/mm.h       | 3 ++-
 include/linux/mm_types.h | 2 ++
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index e1a84b1e6787..7f7aa3f0a396 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -461,7 +461,8 @@ static inline bool fault_flag_allow_retry_first(enum fault_flag flags)
 	{ FAULT_FLAG_USER,		"USER" }, \
 	{ FAULT_FLAG_REMOTE,		"REMOTE" }, \
 	{ FAULT_FLAG_INSTRUCTION,	"INSTRUCTION" }, \
-	{ FAULT_FLAG_INTERRUPTIBLE,	"INTERRUPTIBLE" }
+	{ FAULT_FLAG_INTERRUPTIBLE,	"INTERRUPTIBLE" }, \
+	{ FAULT_FLAG_SPECULATIVE,	"SPECULATIVE" }
 
 /*
  * vm_fault is filled by the pagefault handler and passed to the vma's
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 9db36dc5d4cf..0ae3bf854aad 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -790,6 +790,7 @@ typedef struct {
  * @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_SPECULATIVE: The fault is handled without holding the mmap lock.
  *
  * About @FAULT_FLAG_ALLOW_RETRY and @FAULT_FLAG_TRIED: we can specify
  * whether we would allow page faults to retry by specifying these two
@@ -821,6 +822,7 @@ enum fault_flag {
 	FAULT_FLAG_REMOTE =		1 << 7,
 	FAULT_FLAG_INSTRUCTION =	1 << 8,
 	FAULT_FLAG_INTERRUPTIBLE =	1 << 9,
+	FAULT_FLAG_SPECULATIVE =	1 << 10,
 };
 
 #endif /* _LINUX_MM_TYPES_H */
-- 
2.20.1