Michal Hocko <mhocko@xxxxxxxxxx> writes: > 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. Oh, Yes! I should fix it. Sure, I will add this into the changelog. Best Regards, Huang, Ying -- 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>
