On Tue 24-10-17 23:15:32, Huang, Ying wrote: > Hi, Michal, > > Michal Hocko <mhocko@xxxxxxxxxx> writes: > > > On Tue 24-10-17 10:47:00, Huang, Ying wrote: > >> From: Ying Huang <ying.huang@xxxxxxxxx> > >> > >> __swp_swapcount() is used in __read_swap_cache_async(). Where the > >> invalid swap entry (offset > max) may be supplied during swap > >> readahead. But __swp_swapcount() will print error message for these > >> expected invalid swap entry as below, which will make the users > >> confusing. > > ^^ > > confused... And I have to admit this changelog has left me confused as > > well. What is an invalid swap entry in the readahead? Ohh, let me > > re-real Fixes: commit. It didn't really help "We can avoid needlessly > > allocating page for swap slots that are not used by anyone. No pages > > have to be read in for these slots." > > > > Could you be more specific about when and how this happens please? > > Sorry for confusing. > > When page fault occurs for a swap entry, the original swap readahead > (not new VMA base swap readahead) may readahead several swap entries > after the fault swap entry. The readahead algorithm calculates some of > the swap entries to readahead via increasing the offset of the fault > swap entry without checking whether they are beyond the end of the swap > device and it rely on the __swp_swapcount() and swapcache_prepare() to > check it. Although __swp_swapcount() checks for the swap entry passed > in, it will complain with error message for the expected invalid swap > entry. This makes the end user confusing. > > Is this a little clearer. yes, this makes more sense (modulo the same typo ;)). Can you make this information into the changelog please? Thanks. -- Michal Hocko SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
