On Wed, Mar 30, 2022 at 08:54:09AM -0700, Christoph Hellwig wrote: > On Wed, Mar 30, 2022 at 11:45:56AM -0400, Johannes Weiner wrote: > > > FYI, I started redoing that version and I think with all the cleanups > > > to filemap.c and the readahead code this can be done fairly nicely now: > > > > > > http://git.infradead.org/users/hch/block.git/commitdiff/666abb29c6db870d3941acc5ac19e83fbc72cfd4 > > > > Yes, it's definitely much nicer now with the MM instantiating the > > pages for ->readpage(s). > > > > But AFAICS this breaks compressed btrfs (and erofs?) because those > > still do additional add_to_page_cache_lru() and bio submissions. > > In btrfs, add_ra_bio_pages only passed freshly allocated pages to > add_to_page_cache_lru. These can't really have PageWorkingSet set, > can they? In erofs they can also come from a local page pool, but > I think otherwise the same applies. It's add_to_page_cache_lru() that sets the flag. Basically, when a PageWorkingset (hot) page gets reclaimed, the bit is stored in the vacated tree slot. When the entry is brought back in, add_to_page_cache_lru() transfers it to the newly allocated page. add_to_page_cache_lru() filemap_add_folio() __filemap_add_folio(mapping, folio, index, gfp, &shadow) *shadow = *slot *slot = folio if (shadow) workingset_refault(folio, shadow) folio_set_workingset()
