From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wj0-f198.google.com (mail-wj0-f198.google.com [209.85.210.198]) by kanga.kvack.org (Postfix) with ESMTP id D0B7E6B0038 for ; Wed, 30 Nov 2016 03:08:46 -0500 (EST) Received: by mail-wj0-f198.google.com with SMTP id o2so23812128wje.5 for ; Wed, 30 Nov 2016 00:08:46 -0800 (PST) Received: from mx2.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id m70si5862917wmg.143.2016.11.30.00.08.45 for (version=TLS1 cipher=AES128-SHA bits=128/128); Wed, 30 Nov 2016 00:08:45 -0800 (PST) Date: Wed, 30 Nov 2016 09:08:41 +0100 From: Jan Kara Subject: Re: [PATCH 2/6] mm: Invalidate DAX radix tree entries only if appropriate Message-ID: <20161130080841.GD16667@quack2.suse.cz> References: <1479980796-26161-1-git-send-email-jack@suse.cz> <1479980796-26161-3-git-send-email-jack@suse.cz> <20161129193403.GA12396@cmpxchg.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20161129193403.GA12396@cmpxchg.org> Sender: owner-linux-mm@kvack.org List-ID: To: Johannes Weiner Cc: Jan Kara , linux-fsdevel@vger.kernel.org, Ross Zwisler , linux-ext4@vger.kernel.org, linux-mm@kvack.org, linux-nvdimm@lists.01.org Hi Johannes, On Tue 29-11-16 14:34:03, Johannes Weiner wrote: > On Thu, Nov 24, 2016 at 10:46:32AM +0100, Jan Kara wrote: > > @@ -452,16 +452,37 @@ void dax_wake_mapping_entry_waiter(struct address_space *mapping, > > __wake_up(wq, TASK_NORMAL, wake_all ? 0 : 1, &key); > > } > > > > +static int __dax_invalidate_mapping_entry(struct address_space *mapping, > > + pgoff_t index, bool trunc) > > +{ > > + int ret = 0; > > + void *entry; > > + struct radix_tree_root *page_tree = &mapping->page_tree; > > + > > + spin_lock_irq(&mapping->tree_lock); > > + entry = get_unlocked_mapping_entry(mapping, index, NULL); > > + if (!entry || !radix_tree_exceptional_entry(entry)) > > + goto out; > > + if (!trunc && > > + (radix_tree_tag_get(page_tree, index, PAGECACHE_TAG_DIRTY) || > > + radix_tree_tag_get(page_tree, index, PAGECACHE_TAG_TOWRITE))) > > + goto out; > > + radix_tree_delete(page_tree, index); > > You could use the new __radix_tree_replace() here and save a second > tree lookup. Hum, I'd need to return 'node' from get_unlocked_mapping_entry(). So probably I'll do it in a patch separate from this fix. But thanks for suggestion. > > +/* > > + * Invalidate exceptional DAX entry if easily possible. This handles DAX > > + * entries for invalidate_inode_pages() so we evict the entry only if we can > > + * do so without blocking. > > + */ > > +int dax_invalidate_mapping_entry(struct address_space *mapping, pgoff_t index) > > +{ > > + int ret = 0; > > + void *entry, **slot; > > + struct radix_tree_root *page_tree = &mapping->page_tree; > > + > > + spin_lock_irq(&mapping->tree_lock); > > + entry = __radix_tree_lookup(page_tree, index, NULL, &slot); > > + if (!entry || !radix_tree_exceptional_entry(entry) || > > + slot_locked(mapping, slot)) > > + goto out; > > + if (radix_tree_tag_get(page_tree, index, PAGECACHE_TAG_DIRTY) || > > + radix_tree_tag_get(page_tree, index, PAGECACHE_TAG_TOWRITE)) > > + goto out; > > + radix_tree_delete(page_tree, index); > > Ditto for __radix_tree_replace(). Yes, here I can do it easily rightaway. > > @@ -30,14 +30,6 @@ static void clear_exceptional_entry(struct address_space *mapping, > > struct radix_tree_node *node; > > void **slot; > > > > - /* Handled by shmem itself */ > > - if (shmem_mapping(mapping)) > > - return; > > - > > - if (dax_mapping(mapping)) { > > - dax_delete_mapping_entry(mapping, index); > > - return; > > - } > > spin_lock_irq(&mapping->tree_lock); > > /* > > * Regular page slots are stabilized by the page lock even > > @@ -70,6 +62,56 @@ static void clear_exceptional_entry(struct address_space *mapping, > > spin_unlock_irq(&mapping->tree_lock); > > } > > > > +/* > > + * Unconditionally remove exceptional entry. Usually called from truncate path. > > + */ > > +static void truncate_exceptional_entry(struct address_space *mapping, > > + pgoff_t index, void *entry) > > +{ > > + /* Handled by shmem itself */ > > + if (shmem_mapping(mapping)) > > + return; > > + > > + if (dax_mapping(mapping)) { > > + dax_delete_mapping_entry(mapping, index); > > + return; > > + } > > + clear_exceptional_entry(mapping, index, entry); > > +} > > + > > +/* > > + * Invalidate exceptional entry if easily possible. This handles exceptional > > + * entries for invalidate_inode_pages() so for DAX it evicts only unlocked and > > + * clean entries. > > + */ > > +static int invalidate_exceptional_entry(struct address_space *mapping, > > + pgoff_t index, void *entry) > > +{ > > + /* Handled by shmem itself */ > > + if (shmem_mapping(mapping)) > > + return 1; > > + if (dax_mapping(mapping)) > > + return dax_invalidate_mapping_entry(mapping, index); > > + clear_exceptional_entry(mapping, index, entry); > > + return 1; > > +} > > + > > +/* > > + * Invalidate exceptional entry if clean. This handles exceptional entries for > > + * invalidate_inode_pages2() so for DAX it evicts only clean entries. > > + */ > > +static int invalidate_exceptional_entry2(struct address_space *mapping, > > + pgoff_t index, void *entry) > > +{ > > + /* Handled by shmem itself */ > > + if (shmem_mapping(mapping)) > > + return 1; > > + if (dax_mapping(mapping)) > > + return dax_invalidate_clean_mapping_entry(mapping, index); > > + clear_exceptional_entry(mapping, index, entry); > > + return 1; > > +} > > The way these functions are split out looks fine to me. > > Now that clear_exceptional_entry() doesn't handle shmem and DAX > anymore, only shadows, could you rename it to clear_shadow_entry()? Sure. Done. > The naming situation with truncate, invalidate, invalidate2 worries me > a bit. They aren't great names to begin with, but now DAX uses yet > another terminology for what state prevents a page from being dropped. > Can we switch to truncate, invalidate, and invalidate_sync throughout > truncate.c and then have DAX follow that naming too? Or maybe you can > think of better names. But neither invalidate2 and invalidate_clean > don't seem to capture it quite right ;) Yeah, the naming is confusing. I like the invalidate_sync proposal however renaming invalidate_inode_pages2() to invalidate_inode_pages_sync() is a larger undertaking - grep shows 51 places need to be changed. So I don't want to do it in this patch set. I can call the function dax_invalidate_mapping_entry_sync() if it makes you happier and do the rest later... OK? Honza -- Jan Kara SUSE Labs, CR -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org