romfs: fix romfs_get_unmapped_area() argument check

romfs_get_unmapped_area() checks argument `len' without considering
PAGE_ALIGN which will cause do_mmap_pgoff() return -EINVAL error after
commit f67d9b1576c ("nommu: add page_align to mmap").

Fix the check by changing it in same way ramfs_nommu_get_unmapped_area()
was changed in ramfs/file-nommu.c.

Signed-off-by: Bob Liu <lliubbo@gmail.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Paul Mundt <lethal@linux-sh.org>
Acked-by: Greg Ungerer <gerg@snapgear.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/romfs/mmap-nommu.c

@@ -27,14 +27,18 @@ static unsigned long romfs_get_unmapped_area(struct file *file,
 {
 	struct inode *inode = file->f_mapping->host;
 	struct mtd_info *mtd = inode->i_sb->s_mtd;
-	unsigned long isize, offset;
+	unsigned long isize, offset, maxpages, lpages;
 
 	if (!mtd)
 		goto cant_map_directly;
 
+	/* the mapping mustn't extend beyond the EOF */
+	lpages = (len + PAGE_SIZE - 1) >> PAGE_SHIFT;
 	isize = i_size_read(inode);
 	offset = pgoff << PAGE_SHIFT;
-	if (offset > isize || len > isize || offset > isize - len)
+
+	maxpages = (isize + PAGE_SIZE - 1) >> PAGE_SHIFT;
+	if ((pgoff >= maxpages) || (maxpages - pgoff < lpages))
 		return (unsigned long) -EINVAL;
 
 	/* we need to call down to the MTD layer to do the actual mapping */