Wei Yang <richard.weiy...@gmail.com> writes: > On Fri, May 01, 2020 at 03:48:53PM -0700, Andrew Morton wrote: >>On Fri, 1 May 2020 01:52:59 +0000 Wei Yang <richard.weiy...@gmail.com> wrote: >> >>> When the condition is true, there are two possibilities: >> >>I'm struggling with this one. >> >>> 1. count == SWAP_MAP_BAD >>> 2. count == (SWAP_MAP_MAX & COUNT_CONTINUED) == SWAP_MAP_SHMEM >> >>I'm not sure what 2. is trying to say. For a start, (SWAP_MAP_MAX & >>COUNT_CONTINUED) is zero. I guess it meant "|"? > > Oops, you are right. It should be (SWAP_MAP_MAX | COUNT_CONTINUED). > > Sorry for the confusion. > >> >>Also, the return value documentation says we return EINVAL for migration >>entries. Where's that happening, or is the comment out of date? >> > > Not paid attention to this. > > Take look into the code, I don't find a relationship between the swap count > and migration. Seems we just make a migration entry but not duplicate it. > If my understanding is correct.
Per my understanding, one functionality of the error path is to catch the behavior that shouldn't happen at all. For example, if __swap_duplicate() is called for the migration entry because of some race condition. Best Regards, Huang, Ying
