> What I recommend is below. (Please see the newest -mm because of a bug fix for > mem cgroup) Considering page management on radix-tree, it can be considerd as > a kind of page-migration, which replaces pages on radix-tree. > > == > > > +int replace_page_cache_page(struct page *old, struct page *new, gfp_t gfp_mask) > > +{ > > + int error; > > + > > + VM_BUG_ON(!PageLocked(old)); > > + VM_BUG_ON(!PageLocked(new)); > > + VM_BUG_ON(new->mapping); > > + > struct mem_cgroup *memcg; > I think it should be initialized to NULL. > error = mem_cgroup_prepare_migration(old, new, &memcg); I want some comments like: /* * This is not page migration, but prepare_migration and end_migration * does enough work for charge replacement. */ > # > # This function will charge against "newpage". But this expects > # the caller allows GFP_KERNEL gfp_mask. > # After this, the newpage is in "charged" state. > if (error) > return -ENOMEM; > > > + error = radix_tree_preload(gfp_mask & ~__GFP_HIGHMEM); > > + if (!error) { > > + struct address_space *mapping = old->mapping; > > + pgoff_t offset = old->index; > > + > > + page_cache_get(new); > > + new->mapping = mapping; > > + new->index = offset; > > + > > + spin_lock_irq(&mapping->tree_lock); > > + __remove_from_page_cache(old); > > + error = radix_tree_insert(&mapping->page_tree, offset, new); > > + BUG_ON(error); > > + mapping->nrpages++; > > + __inc_zone_page_state(new, NR_FILE_PAGES); > > + if (PageSwapBacked(new)) > > + __inc_zone_page_state(new, NR_SHMEM); > > + spin_unlock_irq(&mapping->tree_lock); > > + radix_tree_preload_end(); > > > + mem_cgroup_replace_cache_page(old, new); <== remove this. > > mem_cgroup_end_migraton(memcg, old, new, true); > > > + page_cache_release(old); > > + } > else > mem_cgroup_end_migration(memcg, old, new, false); > > # Here, if the 4th argument is true, old page is uncharged. > # if the 4th argument is false, the new page is uncharged. > # Then, "charge" of the old page will be migrated onto the new page > # if replacement is done. > > > > > + > > + return error; > > +} > > +EXPORT_SYMBOL_GPL(replace_page_cache_page); > > + > > == > > I think this is enough simple and this covers all memory cgroup's racy > problems. > I agree. Thanks, Daisuke Nishimura. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom policy in Canada: sign http://dissolvethecrtc.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>