linux-kernel - [PATCH 1/2] userfaultfd: handle dup

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Message-ID: <20241209132549.2878604-2-ruanjinjie@huawei.com>
Date: Mon, 9 Dec 2024 21:25:48 +0800
From: Jinjie Ruan <ruanjinjie@...wei.com>
To: <viro@...iv.linux.org.uk>, <brauner@...nel.org>, <jack@...e.cz>,
	<akpm@...ux-foundation.org>, <Liam.Howlett@...cle.com>,
	<lokeshgidra@...gle.com>, <lorenzo.stoakes@...cle.com>, <rppt@...nel.org>,
	<aarcange@...hat.com>, <ruanjinjie@...wei.com>, <Jason@...c4.com>,
	<linux-fsdevel@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<linux-mm@...ck.org>
Subject: [PATCH 1/2] userfaultfd: handle dup_userfaultfd() NULL check inline

Make the NULL check for vma's userfaultfd ctx inline, so we can
avoid the function call overhead if the ctx is NULL.

Signed-off-by: Jinjie Ruan <ruanjinjie@...wei.com>
---
 fs/userfaultfd.c              |  5 +----
 include/linux/userfaultfd_k.h | 11 ++++++++++-
 2 files changed, 11 insertions(+), 5 deletions(-)

diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
index 7c0bd0b55f88..7e551c234832 100644
--- a/fs/userfaultfd.c
+++ b/fs/userfaultfd.c
@@ -615,15 +615,12 @@ static void userfaultfd_event_complete(struct userfaultfd_ctx *ctx,
 	__remove_wait_queue(&ctx->event_wqh, &ewq->wq);
 }
 
-int dup_userfaultfd(struct vm_area_struct *vma, struct list_head *fcs)
+int __dup_userfaultfd(struct vm_area_struct *vma, struct list_head *fcs)
 {
 	struct userfaultfd_ctx *ctx = NULL, *octx;
 	struct userfaultfd_fork_ctx *fctx;
 
 	octx = vma->vm_userfaultfd_ctx.ctx;
-	if (!octx)
-		return 0;
-
 	if (!(octx->features & UFFD_FEATURE_EVENT_FORK)) {
 		userfaultfd_reset_ctx(vma);
 		return 0;
diff --git a/include/linux/userfaultfd_k.h b/include/linux/userfaultfd_k.h
index cb40f1a1d081..06b47104aa1a 100644
--- a/include/linux/userfaultfd_k.h
+++ b/include/linux/userfaultfd_k.h
@@ -247,7 +247,16 @@ static inline bool vma_can_userfault(struct vm_area_struct *vma,
 	    vma_is_shmem(vma);
 }
 
-extern int dup_userfaultfd(struct vm_area_struct *, struct list_head *);
+int __dup_userfaultfd(struct vm_area_struct *, struct list_head *);
+static inline int dup_userfaultfd(struct vm_area_struct *vma,
+				  struct list_head *fcs)
+{
+	if (likely(!vma->vm_userfaultfd_ctx.ctx))
+		return 0;
+
+	return __dup_userfaultfd(vma, fcs);
+}
+
 extern void dup_userfaultfd_complete(struct list_head *);
 void dup_userfaultfd_fail(struct list_head *);
 
-- 
2.34.1