mm: fix some spelling mistakes in comments

Fix some spelling mistakes in comments:
	udpate ==> update
	succesful ==> successful
	exmaple ==> example
	unneccessary ==> unnecessary
	stoping ==> stopping
	uknown ==> unknown

Link: https://lkml.kernel.org/r/20201127011747.86005-1-shihaitao1@huawei.com
Signed-off-by: Haitao Shi <shihaitao1@huawei.com>
Reviewed-by: Mike Rapoport <rppt@linux.ibm.com>
Reviewed-by: Souptick Joarder <jrdr.linux@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/filemap.c

@@ -1359,7 +1359,7 @@ static int __wait_on_page_locked_async(struct page *page,
 	else
 		ret = PageLocked(page);
 	/*
-	 * If we were succesful now, we know we're still on the
+	 * If we were successful now, we know we're still on the
 	 * waitqueue as we're still under the lock. This means it's
 	 * safe to remove and return success, we know the callback
 	 * isn't going to trigger.

mm/huge_memory.c

@@ -2391,7 +2391,7 @@ static void __split_huge_page_tail(struct page *head, int tail,
 	 * Clone page flags before unfreezing refcount.
 	 *
 	 * After successful get_page_unless_zero() might follow flags change,
-	 * for exmaple lock_page() which set PG_waiters.
+	 * for example lock_page() which set PG_waiters.
 	 */
 	page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP;
 	page_tail->flags |= (head->flags &

mm/khugepaged.c

@@ -1275,7 +1275,7 @@ static int khugepaged_scan_pmd(struct mm_struct *mm,
 			 * PTEs are armed with uffd write protection.
 			 * Here we can also mark the new huge pmd as
 			 * write protected if any of the small ones is
-			 * marked but that could bring uknown
+			 * marked but that could bring unknown
 			 * userfault messages that falls outside of
 			 * the registered range.  So, just be simple.
 			 */

mm/memblock.c

@@ -871,7 +871,7 @@ int __init_memblock memblock_physmem_add(phys_addr_t base, phys_addr_t size)
  * @base: base address of the region
  * @size: size of the region
  * @set: set or clear the flag
- * @flag: the flag to udpate
+ * @flag: the flag to update
  *
  * This function isolates region [@base, @base + @size), and sets/clears flag
  *

mm/migrate.c

@@ -2594,7 +2594,7 @@ static bool migrate_vma_check_page(struct page *page)
 		 * will bump the page reference count. Sadly there is no way to
 		 * differentiate a regular pin from migration wait. Hence to
 		 * avoid 2 racing thread trying to migrate back to CPU to enter
-		 * infinite loop (one stoping migration because the other is
+		 * infinite loop (one stopping migration because the other is
 		 * waiting on pte migration entry). We always return true here.
 		 *
 		 * FIXME proper solution is to rework migration_entry_wait() so

mm/page_ext.c

@@ -34,7 +34,7 @@
  *
  * The need callback is used to decide whether extended memory allocation is
  * needed or not. Sometimes users want to deactivate some features in this
- * boot and extra memory would be unneccessary. In this case, to avoid
+ * boot and extra memory would be unnecessary. In this case, to avoid
  * allocating huge chunk of memory, each clients represent their need of
  * extra memory through the need callback. If one of the need callbacks
  * returns true, it means that someone needs extra memory so that