[PATCH -v5 1/2] Massive code cleanup of sys_msync()

[Anton Salikhmetov <salikhmetov@gmail.com>]

Substantial code cleanup of the sys_msync() function:

1) using the PAGE_ALIGN() macro instead of "manual" alignment;
2) improved readability of the loop traversing the process memory regions.

Signed-off-by: Anton Salikhmetov <salikhmetov@gmail.com>
---
 mm/msync.c |   74 +++++++++++++++++++++++++++++------------------------------
 1 files changed, 36 insertions(+), 38 deletions(-)

diff --git a/mm/msync.c b/mm/msync.c
index 144a757..44997bf 100644
--- a/mm/msync.c
+++ b/mm/msync.c
@@ -1,24 +1,22 @@
 /*
- *	linux/mm/msync.c
+ * The msync() system call.
  *
- * Copyright (C) 1994-1999  Linus Torvalds
+ * Copyright (C) 1994-1999 Linus Torvalds
+ * Copyright (C) 2008 Anton Salikhmetov <salikhmetov@gmail.com>
  */
 
-/*
- * The msync() system call.
- */
+#include <linux/file.h>
 #include <linux/fs.h>
 #include <linux/mm.h>
 #include <linux/mman.h>
-#include <linux/file.h>
-#include <linux/syscalls.h>
 #include <linux/sched.h>
+#include <linux/syscalls.h>
 
 /*
  * MS_SYNC syncs the entire file - including mappings.
  *
  * MS_ASYNC does not start I/O (it used to, up to 2.5.67).
- * Nor does it marks the relevant pages dirty (it used to up to 2.6.17).
+ * Nor does it mark the relevant pages dirty (it used to up to 2.6.17).
  * Now it doesn't do anything, since dirty pages are properly tracked.
  *
  * The application may now run fsync() to
@@ -33,8 +31,7 @@ asmlinkage long sys_msync(unsigned long start, size_t len, int flags)
 	unsigned long end;
 	struct mm_struct *mm = current->mm;
 	struct vm_area_struct *vma;
-	int unmapped_error = 0;
-	int error = -EINVAL;
+	int error = -EINVAL, unmapped_error = 0;
 
 	if (flags & ~(MS_ASYNC | MS_INVALIDATE | MS_SYNC))
 		goto out;
@@ -42,62 +39,63 @@ asmlinkage long sys_msync(unsigned long start, size_t len, int flags)
 		goto out;
 	if ((flags & MS_ASYNC) && (flags & MS_SYNC))
 		goto out;
-	error = -ENOMEM;
-	len = (len + ~PAGE_MASK) & PAGE_MASK;
+
+	len = PAGE_ALIGN(len);
 	end = start + len;
-	if (end < start)
+	if (end < start) {
+		error = -ENOMEM;
 		goto out;
+	}
+
 	error = 0;
+
 	if (end == start)
 		goto out;
+
 	/*
 	 * If the interval [start,end) covers some unmapped address ranges,
 	 * just ignore them, but return -ENOMEM at the end.
 	 */
 	down_read(&mm->mmap_sem);
 	vma = find_vma(mm, start);
-	for (;;) {
+	do {
 		struct file *file;
 
-		/* Still start < end. */
-		error = -ENOMEM;
-		if (!vma)
-			goto out_unlock;
-		/* Here start < vma->vm_end. */
+		if (!vma) {
+			error = -ENOMEM;
+			break;
+		}
 		if (start < vma->vm_start) {
 			start = vma->vm_start;
-			if (start >= end)
-				goto out_unlock;
+			if (start >= end) {
+				error = -ENOMEM;
+				break;
+			}
 			unmapped_error = -ENOMEM;
 		}
-		/* Here vma->vm_start <= start < vma->vm_end. */
-		if ((flags & MS_INVALIDATE) &&
-				(vma->vm_flags & VM_LOCKED)) {
+		if ((flags & MS_INVALIDATE) && (vma->vm_flags & VM_LOCKED)) {
 			error = -EBUSY;
-			goto out_unlock;
+			break;
 		}
-		file = vma->vm_file;
 		start = vma->vm_end;
-		if ((flags & MS_SYNC) && file &&
-				(vma->vm_flags & VM_SHARED)) {
+
+		file = vma->vm_file;
+		if (file && (vma->vm_flags & VM_SHARED) && (flags & MS_SYNC)) {
 			get_file(file);
 			up_read(&mm->mmap_sem);
 			error = do_fsync(file, 0);
 			fput(file);
-			if (error || start >= end)
+			if (error)
 				goto out;
 			down_read(&mm->mmap_sem);
 			vma = find_vma(mm, start);
-		} else {
-			if (start >= end) {
-				error = 0;
-				goto out_unlock;
-			}
-			vma = vma->vm_next;
+			continue;
 		}
-	}
-out_unlock:
+
+		vma = vma->vm_next;
+	} while (start < end);
 	up_read(&mm->mmap_sem);
+
 out:
-	return error ? : unmapped_error;
+	return error ? error : unmapped_error;
 }
-- 
1.4.4.4