[PATH][RFC] mm: Move common segments checks to separate function

[Dmitriy Monakhov]

Move common segments checks from  __generic_file_aio_{read,write}_nolock()
to separate helper function generic_segment_checks(). 

Signed-off-by: Dmitriy Monakhov <dmonakhov@xxxxxxxxxx>
-------
diff --git a/mm/filemap.c b/mm/filemap.c
index 8332c77..d01abb6 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1126,6 +1126,38 @@ success:
 	return size;
 }
 
+/*
+ * Performs necessary segments checks.
+ * Returns bytes count or appropriate error code that caller should return.
+ */
+static ssize_t 
+generic_segment_checks(unsigned long nr_segs, const struct iovec *iov,
+			unsigned long access_flag)
+{
+	size_t bcount;
+	unsigned long	seg;
+	bcount = 0;
+	for (seg = 0; seg < nr_segs; seg++) {
+		const struct iovec *iv = &iov[seg];
+		
+		/*
+		 * If any segment has a negative length, or the cumulative
+		 * length ever wraps negative then return -EINVAL.
+		 */
+		bcount += iv->iov_len;
+		if (unlikely((ssize_t)(bcount|iv->iov_len) < 0))
+			return -EINVAL;
+		if (access_ok(access_flag, iv->iov_base, iv->iov_len))
+			continue;
+		if (seg == 0)
+			return -EFAULT;
+		nr_segs = seg;
+		bcount -= iv->iov_len;	/* This segment is no good */
+		break;
+	}
+	return bcount;
+}
+
 /**
  * generic_file_aio_read - generic filesystem read routine
  * @iocb:	kernel I/O control block
@@ -1146,25 +1178,7 @@ generic_file_aio_read(struct kiocb *iocb
 	size_t count;
 	loff_t *ppos = &iocb->ki_pos;
 
-	count = 0;
-	for (seg = 0; seg < nr_segs; seg++) {
-		const struct iovec *iv = &iov[seg];
-
-		/*
-		 * If any segment has a negative length, or the cumulative
-		 * length ever wraps negative then return -EINVAL.
-		 */
-		count += iv->iov_len;
-		if (unlikely((ssize_t)(count|iv->iov_len) < 0))
-			return -EINVAL;
-		if (access_ok(VERIFY_WRITE, iv->iov_base, iv->iov_len))
-			continue;
-		if (seg == 0)
-			return -EFAULT;
-		nr_segs = seg;
-		count -= iv->iov_len;	/* This segment is no good */
-		break;
-	}
+	count = generic_segment_checks(nr_segs, iov, VERIFY_WRITE);
 
 	/* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
 	if (filp->f_flags & O_DIRECT) {
@@ -2225,31 +2239,11 @@ __generic_file_aio_write_nolock(struct k
 	size_t ocount;		/* original count */
 	size_t count;		/* after file limit checks */
 	struct inode 	*inode = mapping->host;
-	unsigned long	seg;
 	loff_t		pos;
 	ssize_t		written;
 	ssize_t		err;
 
-	ocount = 0;
-	for (seg = 0; seg < nr_segs; seg++) {
-		const struct iovec *iv = &iov[seg];
-
-		/*
-		 * If any segment has a negative length, or the cumulative
-		 * length ever wraps negative then return -EINVAL.
-		 */
-		ocount += iv->iov_len;
-		if (unlikely((ssize_t)(ocount|iv->iov_len) < 0))
-			return -EINVAL;
-		if (access_ok(VERIFY_READ, iv->iov_base, iv->iov_len))
-			continue;
-		if (seg == 0)
-			return -EFAULT;
-		nr_segs = seg;
-		ocount -= iv->iov_len;	/* This segment is no good */
-		break;
-	}
-
+	ocount = generic_segment_checks(nr_segs, iov, VERIFY_READ);
 	count = ocount;
 	pos = *ppos;