new helper: vm_mmap_pgoff()

take it to mm/util.c, convert vm_mmap() to use of that one and
take it to mm/util.c as well, convert both sys_mmap_pgoff() to
use of vm_mmap_pgoff()
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

mm/internal.h

@@ -342,3 +342,7 @@ extern u64 hwpoison_filter_flags_mask;
 extern u64 hwpoison_filter_flags_value;
 extern u64 hwpoison_filter_memcg;
 extern u32 hwpoison_filter_enable;
+
+extern unsigned long vm_mmap_pgoff(struct file *, unsigned long,
+        unsigned long, unsigned long,
+        unsigned long, unsigned long);

mm/mmap.c

@@ -1102,28 +1102,6 @@ unsigned long do_mmap_pgoff(struct file *file, unsigned long addr,
 	return mmap_region(file, addr, len, flags, vm_flags, pgoff);
 }
 
-unsigned long vm_mmap(struct file *file, unsigned long addr,
-	unsigned long len, unsigned long prot,
-	unsigned long flag, unsigned long offset)
-{
-	unsigned long ret;
-	struct mm_struct *mm = current->mm;
-
-	if (unlikely(offset + PAGE_ALIGN(len) < offset))
-		return -EINVAL;
-	if (unlikely(offset & ~PAGE_MASK))
-		return -EINVAL;
-
-	ret = security_mmap_file(file, prot, flag);
-	if (!ret) {
-		down_write(&mm->mmap_sem);
-		ret = do_mmap_pgoff(file, addr, len, prot, flag, offset >> PAGE_SHIFT);
-		up_write(&mm->mmap_sem);
-	}
-	return ret;
-}
-EXPORT_SYMBOL(vm_mmap);
-
 SYSCALL_DEFINE6(mmap_pgoff, unsigned long, addr, unsigned long, len,
 		unsigned long, prot, unsigned long, flags,
 		unsigned long, fd, unsigned long, pgoff)
@@ -1155,13 +1133,7 @@ SYSCALL_DEFINE6(mmap_pgoff, unsigned long, addr, unsigned long, len,
 
 	flags &= ~(MAP_EXECUTABLE | MAP_DENYWRITE);
 
-	retval = security_mmap_file(file, prot, flags);
-	if (!retval) {
-		down_write(&current->mm->mmap_sem);
-		retval = do_mmap_pgoff(file, addr, len, prot, flags, pgoff);
-		up_write(&current->mm->mmap_sem);
-	}
-
+	retval = vm_mmap_pgoff(file, addr, len, prot, flags, pgoff);
 	if (file)
 		fput(file);
 out:

mm/nommu.c

@@ -1470,28 +1470,6 @@ unsigned long do_mmap_pgoff(struct file *file,
 	return -ENOMEM;
 }
 
-unsigned long vm_mmap(struct file *file, unsigned long addr,
-	unsigned long len, unsigned long prot,
-	unsigned long flag, unsigned long offset)
-{
-	unsigned long ret;
-	struct mm_struct *mm = current->mm;
-
-	if (unlikely(offset + PAGE_ALIGN(len) < offset))
-		return -EINVAL;
-	if (unlikely(offset & ~PAGE_MASK))
-		return -EINVAL;
-
-	ret = security_mmap_file(file, prot, flag);
-	if (!ret) {
-		down_write(&mm->mmap_sem);
-		ret = do_mmap_pgoff(file, addr, len, prot, flag, offset >> PAGE_SHIFT);
-		up_write(&mm->mmap_sem);
-	}
-	return ret;
-}
-EXPORT_SYMBOL(vm_mmap);
-
 SYSCALL_DEFINE6(mmap_pgoff, unsigned long, addr, unsigned long, len,
 		unsigned long, prot, unsigned long, flags,
 		unsigned long, fd, unsigned long, pgoff)
@@ -1508,12 +1486,7 @@ SYSCALL_DEFINE6(mmap_pgoff, unsigned long, addr, unsigned long, len,
 
 	flags &= ~(MAP_EXECUTABLE | MAP_DENYWRITE);
 
-	ret = security_mmap_file(file, prot, flags);
-	if (!ret) {
-		down_write(&current->mm->mmap_sem);
-		retval = do_mmap_pgoff(file, addr, len, prot, flags, pgoff);
-		up_write(&current->mm->mmap_sem);
-	}
+	ret = vm_mmap_pgoff(file, addr, len, prot, flags, pgoff);
 
 	if (file)
 		fput(file);

mm/util.c

@@ -4,6 +4,7 @@
 #include <linux/export.h>
 #include <linux/err.h>
 #include <linux/sched.h>
+#include <linux/security.h>
 #include <asm/uaccess.h>
 
 #include "internal.h"
@@ -341,6 +342,35 @@ int __attribute__((weak)) get_user_pages_fast(unsigned long start,
 }
 EXPORT_SYMBOL_GPL(get_user_pages_fast);
 
+unsigned long vm_mmap_pgoff(struct file *file, unsigned long addr,
+	unsigned long len, unsigned long prot,
+	unsigned long flag, unsigned long pgoff)
+{
+	unsigned long ret;
+	struct mm_struct *mm = current->mm;
+
+	ret = security_mmap_file(file, prot, flag);
+	if (!ret) {
+		down_write(&mm->mmap_sem);
+		ret = do_mmap_pgoff(file, addr, len, prot, flag, pgoff);
+		up_write(&mm->mmap_sem);
+	}
+	return ret;
+}
+
+unsigned long vm_mmap(struct file *file, unsigned long addr,
+	unsigned long len, unsigned long prot,
+	unsigned long flag, unsigned long offset)
+{
+	if (unlikely(offset + PAGE_ALIGN(len) < offset))
+		return -EINVAL;
+	if (unlikely(offset & ~PAGE_MASK))
+		return -EINVAL;
+
+	return vm_mmap_pgoff(file, addr, len, prot, flag, offset >> PAGE_SHIFT);
+}
+EXPORT_SYMBOL(vm_mmap);
+
 /* Tracepoints definitions. */
 EXPORT_TRACEPOINT_SYMBOL(kmalloc);
 EXPORT_TRACEPOINT_SYMBOL(kmem_cache_alloc);