mm: move common segment checks to separate helper function (v7)

index dbbac55..621de36 100644
@@ -2129,28 +2129,13 @@ static ssize_t ntfs_file_aio_write_nolock(struct kiocb *iocb,
 	struct address_space *mapping = file->f_mapping;
 	struct inode *inode = mapping->host;
 	loff_t pos;
-	unsigned long seg;
 	size_t count;		/* after file limit checks */
 	ssize_t written, err;
 
 	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_READ, iv->iov_base, iv->iov_len))
-			continue;
-		if (!seg)
-			return -EFAULT;
-		nr_segs = seg;
-		count -= iv->iov_len;	/* This segment is no good */
-		break;
-	}
+	err = generic_segment_checks(iov, &nr_segs, &count, VERIFY_READ);
+	if (err)
+		return err;
 	pos = *ppos;
 	vfs_check_frozen(inode->i_sb, SB_FREEZE_WRITE);
 	/* We can write back this queue in page reclaim. */

index ff8d64e..558076d 100644
@@ -639,7 +639,6 @@ xfs_write(
 	xfs_fsize_t		isize, new_size;
 	xfs_iocore_t		*io;
 	bhv_vnode_t		*vp;
-	unsigned long		seg;
 	int			iolock;
 	int			eventsent = 0;
 	bhv_vrwlock_t		locktype;

@@ -652,24 +651,9 @@ xfs_write(
 	vp = BHV_TO_VNODE(bdp);
 	xip = XFS_BHVTOI(bdp);
 
-	for (seg = 0; seg < segs; seg++) {
-		const struct iovec *iv = &iovp[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;
-		segs = seg;
-		ocount -= iv->iov_len;  /* This segment is no good */
-		break;
-	}
+	error = generic_segment_checks(iovp, &segs, &ocount, VERIFY_READ);
+	if (error)
+		return error;
 
 	count = ocount;
 	pos = *offset;

index 6a3d22e..3b99450 100644
@@ -1778,6 +1778,9 @@ extern ssize_t generic_file_sendfile(struct file *, loff_t *, size_t, read_actor
 extern void do_generic_mapping_read(struct address_space *mapping,
 				    struct file_ra_state *, struct file *,
 				    loff_t *, read_descriptor_t *, read_actor_t);
+extern int generic_segment_checks(const struct iovec *iov,
+		unsigned long *nr_segs, size_t *count,
+		unsigned long access_flags);
 
 /* fs/splice.c */
 extern ssize_t generic_file_splice_read(struct file *, loff_t *,

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