mm: fix kernel-doc markups

Kernel-doc markups should use this format:
        identifier - description

Fix some issues on mm files:

1) The definition for get_user_pages_locked() doesn't follow it.  Also,
   it expects a short descrpition at the header, followed by a long one,
   after the parameters.  Fix it.

2) Kernel-doc requires that a kernel-doc markup to be immediately below
   the function prototype, as otherwise it will rename it.  So, move
   get_pfnblock_flags_mask() description to the right place.

3) Make invalidate_mapping_pagevec() to also follow the expected
   kernel-doc format.

While here, fix a few minor English syntax issues, as suggested
by Matthew:
	will used -> will be used
	similar with -> similar to

Link: https://lkml.kernel.org/r/80e85dddc92d333bc2159ee8a2294921612e8745.1605521731.git.mchehab+huawei@kernel.org
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Suggested-by: Mattew Wilcox <willy@infradead.org>	[English fixes]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/truncate.c b/mm/truncate.c
index c196fad..8aa4907 100644
--- a/mm/truncate.c
+++ b/mm/truncate.c
@@ -643,9 +643,9 @@ EXPORT_SYMBOL(invalidate_mapping_pages);
  * @end: the offset 'to' which to invalidate (inclusive)
  * @nr_pagevec: invalidate failed page number for caller
  *
- * This helper is similar with invalidate_mapping_pages, except that it accounts
- * for pages that failed to invalidate on a pagevec and count them in
- * @nr_pagevec, which will used by the caller.
+ * This helper is similar to invalidate_mapping_pages(), except that it accounts
+ * for pages that are likely on a pagevec and counts them in @nr_pagevec, which
+ * will be used by the caller.
  */
 void invalidate_mapping_pagevec(struct address_space *mapping,
 		pgoff_t start, pgoff_t end, unsigned long *nr_pagevec)