linux-kernel - [PATCH v3 13/23] mm/mmap: Make vm_special

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Message-Id: <20210611180242.711399-14-dima@arista.com>
Date:   Fri, 11 Jun 2021 19:02:32 +0100
From:   Dmitry Safonov <dima@...sta.com>
To:     linux-kernel@...r.kernel.org
Cc:     Dmitry Safonov <0x7f454c46@...il.com>,
        Dmitry Safonov <dima@...sta.com>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Andy Lutomirski <luto@...nel.org>,
        Arnd Bergmann <arnd@...db.de>, Borislav Petkov <bp@...en8.de>,
        Catalin Marinas <catalin.marinas@....com>,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        Guo Ren <guoren@...nel.org>, "H. Peter Anvin" <hpa@...or.com>,
        Ingo Molnar <mingo@...hat.com>,
        Oleg Nesterov <oleg@...hat.com>,
        Russell King <linux@...linux.org.uk>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        Will Deacon <will@...nel.org>, x86@...nel.org
Subject: [PATCH v3 13/23] mm/mmap: Make vm_special_mapping::mremap return void

Previously .mremap() callback had to return (int) to provide
a way to restrict resizing of a special mapping. Now it's
restricted by providing .may_split = special_mapping_split.

Removing (int) return simplifies further changes to
special_mapping_mremap() as it won't need save ret code from the
callback. Also, it removes needless `return 0` from callbacks.

Signed-off-by: Dmitry Safonov <dima@...sta.com>
---
 arch/arm/kernel/process.c | 3 +--
 arch/arm64/kernel/vdso.c  | 4 +---
 arch/mips/vdso/genvdso.c  | 3 +--
 arch/x86/entry/vdso/vma.c | 4 +---
 include/linux/mm_types.h  | 4 ++--
 mm/mmap.c                 | 2 +-
 6 files changed, 7 insertions(+), 13 deletions(-)

diff --git a/arch/arm/kernel/process.c b/arch/arm/kernel/process.c
index 5897ccb88bca..b863c5525b5d 100644
--- a/arch/arm/kernel/process.c
+++ b/arch/arm/kernel/process.c
@@ -387,11 +387,10 @@ static unsigned long sigpage_addr(const struct mm_struct *mm,
 static struct page *signal_page;
 extern struct page *get_signal_page(void);
 
-static int sigpage_mremap(const struct vm_special_mapping *sm,
+static void sigpage_mremap(const struct vm_special_mapping *sm,
 		struct vm_area_struct *new_vma)
 {
 	current->mm->context.sigpage = new_vma->vm_start;
-	return 0;
 }
 
 static const struct vm_special_mapping sigpage_mapping = {
diff --git a/arch/arm64/kernel/vdso.c b/arch/arm64/kernel/vdso.c
index c0512c2e8183..680415e0098c 100644
--- a/arch/arm64/kernel/vdso.c
+++ b/arch/arm64/kernel/vdso.c
@@ -78,12 +78,10 @@ static union {
 } vdso_data_store __page_aligned_data;
 struct vdso_data *vdso_data = vdso_data_store.data;
 
-static int vdso_mremap(const struct vm_special_mapping *sm,
+static void vdso_mremap(const struct vm_special_mapping *sm,
 		struct vm_area_struct *new_vma)
 {
 	current->mm->context.vdso = (void *)new_vma->vm_start;
-
-	return 0;
 }
 
 static int __init __vdso_init(enum vdso_abi abi)
diff --git a/arch/mips/vdso/genvdso.c b/arch/mips/vdso/genvdso.c
index 09e30eb4be86..0303d30cde03 100644
--- a/arch/mips/vdso/genvdso.c
+++ b/arch/mips/vdso/genvdso.c
@@ -259,13 +259,12 @@ int main(int argc, char **argv)
 	fprintf(out_file, "#include <linux/linkage.h>\n");
 	fprintf(out_file, "#include <linux/mm.h>\n");
 	fprintf(out_file, "#include <asm/vdso.h>\n");
-	fprintf(out_file, "static int vdso_mremap(\n");
+	fprintf(out_file, "static void vdso_mremap(\n");
 	fprintf(out_file, "	const struct vm_special_mapping *sm,\n");
 	fprintf(out_file, "	struct vm_area_struct *new_vma)\n");
 	fprintf(out_file, "{\n");
 	fprintf(out_file, "	current->mm->context.vdso =\n");
 	fprintf(out_file, "	(void *)(new_vma->vm_start);\n");
-	fprintf(out_file, "	return 0;\n");
 	fprintf(out_file, "}\n");
 
 	/* Write out the stripped VDSO data. */
diff --git a/arch/x86/entry/vdso/vma.c b/arch/x86/entry/vdso/vma.c
index f1abe43aadb9..a286d44751be 100644
--- a/arch/x86/entry/vdso/vma.c
+++ b/arch/x86/entry/vdso/vma.c
@@ -86,15 +86,13 @@ static void vdso_fix_landing(const struct vdso_image *image,
 #endif
 }
 
-static int vdso_mremap(const struct vm_special_mapping *sm,
+static void vdso_mremap(const struct vm_special_mapping *sm,
 		struct vm_area_struct *new_vma)
 {
 	const struct vdso_image *image = current->mm->context.vdso_image;
 
 	vdso_fix_landing(image, new_vma);
 	current->mm->context.vdso = (void __user *)new_vma->vm_start;
-
-	return 0;
 }
 
 #ifdef CONFIG_TIME_NS
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 5aacc1c10a45..e9c5f2051f08 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -770,8 +770,8 @@ struct vm_special_mapping {
 				struct vm_area_struct *vma,
 				struct vm_fault *vmf);
 
-	int (*mremap)(const struct vm_special_mapping *sm,
-		     struct vm_area_struct *new_vma);
+	void (*mremap)(const struct vm_special_mapping *sm,
+		       struct vm_area_struct *new_vma);
 };
 
 enum tlb_flush_reason {
diff --git a/mm/mmap.c b/mm/mmap.c
index 0584e540246e..4f0d62409b1c 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -3401,7 +3401,7 @@ static int special_mapping_mremap(struct vm_area_struct *new_vma)
 		return -EFAULT;
 
 	if (sm->mremap)
-		return sm->mremap(sm, new_vma);
+		sm->mremap(sm, new_vma);
 
 	return 0;
 }
-- 
2.31.1