mm: add comment on swap_duplicate's error code

swap_duplicate()'s loop appears to miss out on returning the error code from __swap_duplicate(), except when that's -ENOMEM. In fact this is intentional: prior to -ENOMEM for swap_count_continuation, swap_duplicate() was void (and the case only occurs when copy_one_pte() hits a corrupt pte). But that's surprising behaviour, which certainly deserves a comment. Signed-off-by: Hugh Dickins <[email protected]> Reported-by: Huang Shijie <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>
dabrace · Mar 6, 2010 · 08259d5 · 08259d5
1 parent c08c6e1
commit 08259d5
Showing 1 changed file with 5 additions and 1 deletion.
diff --git a/mm/swapfile.c b/mm/swapfile.c
@@ -2161,7 +2161,11 @@ void swap_shmem_alloc(swp_entry_t entry)
 }
 
 /*
- * increase reference count of swap entry by 1.
+ * Increase reference count of swap entry by 1.
+ * Returns 0 for success, or -ENOMEM if a swap_count_continuation is required
+ * but could not be atomically allocated.  Returns 0, just as if it succeeded,
+ * if __swap_duplicate() fails for another reason (-EINVAL or -ENOENT), which
+ * might occur if a page table entry has got corrupted.
  */
 int swap_duplicate(swp_entry_t entry)
 {