On Fri 30-11-18 14:58:10, Josef Bacik wrote: > If we do not have a page at filemap_fault time we'll do this weird > forced page_cache_read thing to populate the page, and then drop it > again and loop around and find it. This makes for 2 ways we can read a > page in filemap_fault, and it's not really needed. Instead add a > FGP_FOR_MMAP flag so that pagecache_get_page() will return a unlocked > page that's in pagecache. Then use the normal page locking and readpage > logic already in filemap_fault. This simplifies the no page in page > cache case significantly. > > Signed-off-by: Josef Bacik <josef@xxxxxxxxxxxxxx> Thanks for the patch. I like the simplification but I think it could be even improved... see below. > @@ -2449,9 +2426,11 @@ vm_fault_t filemap_fault(struct vm_fault *vmf) > count_memcg_event_mm(vmf->vma->vm_mm, PGMAJFAULT); > ret = VM_FAULT_MAJOR; > retry_find: > - page = find_get_page(mapping, offset); > + page = pagecache_get_page(mapping, offset, > + FGP_CREAT|FGP_FOR_MMAP, > + vmf->gfp_mask); > if (!page) > - goto no_cached_page; > + return vmf_error(-ENOMEM); So why don't you just do: page = pagecache_get_page(mapping, offset, FGP_CREAT | FGP_LOCK, vmf->gfp_mask); if (!page) return vmf_error(-ENOMEM); goto check_uptodate; where check_uptodate would be a label before 'PageUptodate' check? Then you don't have to introduce new flag for pagecache_get_page() and you also don't have to unlock and then lock again the page... And you can still delete all the code you've deleted. Honza -- Jan Kara <jack@xxxxxxxx> SUSE Labs, CR
