mm/vmalloc: add code comment for find_vmap_area_exceed_addr()

Its behaviour is like find_vma() which finds an area above the specified
address, add comment to make it easier to understand.

And also fix two places of grammer mistake/typo.

Link: https://lkml.kernel.org/r/20220607105958.382076-5-bhe@redhat.comSigned-off-by: Baoquan He <bhe@redhat.com>
Reviewed-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Cc: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/vmalloc.c

@@ -790,6 +790,7 @@ unsigned long vmalloc_nr_pages(void)
 	return atomic_long_read(&nr_vmalloc_pages);
 }
 
+/* Look up the first VA which satisfies addr < va_end, NULL if none. */
 static struct vmap_area *find_vmap_area_exceed_addr(unsigned long addr)
 {
 	struct vmap_area *va = NULL;
@@ -929,7 +930,7 @@ link_va(struct vmap_area *va, struct rb_root *root,
 		 * Some explanation here. Just perform simple insertion
 		 * to the tree. We do not set va->subtree_max_size to
 		 * its current size before calling rb_insert_augmented().
-		 * It is because of we populate the tree from the bottom
+		 * It is because we populate the tree from the bottom
 		 * to parent levels when the node _is_ in the tree.
 		 *
 		 * Therefore we set subtree_max_size to zero after insertion,
@@ -1655,7 +1656,7 @@ static atomic_long_t vmap_lazy_nr = ATOMIC_LONG_INIT(0);
 
 /*
  * Serialize vmap purging.  There is no actual critical section protected
- * by this look, but we want to avoid concurrent calls for performance
+ * by this lock, but we want to avoid concurrent calls for performance
  * reasons and to make the pcpu_get_vm_areas more deterministic.
  */
 static DEFINE_MUTEX(vmap_purge_lock);