From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 378FAC46467 for ; Mon, 16 Jan 2023 17:16:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234104AbjAPRQO (ORCPT ); Mon, 16 Jan 2023 12:16:14 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41524 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234433AbjAPRPb (ORCPT ); Mon, 16 Jan 2023 12:15:31 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5135A32E6C for ; Mon, 16 Jan 2023 08:56:35 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id BCA96B80E95 for ; Mon, 16 Jan 2023 16:56:33 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2758AC433D2; Mon, 16 Jan 2023 16:56:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1673888192; bh=mQDpWG2/zKLiIt2rCZhhmOBtAz5WWHJLuf9+NMfhhKo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=UJ5RtW9wsOVB8Efe90ATJfXQrvc9z7Xt1WbUueEJ0EfnvVTtigMlywzFJ3mTSuHEH CupZfQjfd44indrfiN0PKCHN4Gmwm30xUfgkuKKPzt9bSjFMtD5/3YxlI5IBeSnicI rexwu1AV5W7UGd4qxZ40/iQTmckgPBcz4/CfeWZI= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Jan Kara , Theodore Tso , Sasha Levin Subject: [PATCH 4.19 436/521] mbcache: add functions to delete entry if unused Date: Mon, 16 Jan 2023 16:51:38 +0100 Message-Id: <20230116154906.652764799@linuxfoundation.org> X-Mailer: git-send-email 2.39.0 In-Reply-To: <20230116154847.246743274@linuxfoundation.org> References: <20230116154847.246743274@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Jan Kara [ Upstream commit 3dc96bba65f53daa217f0a8f43edad145286a8f5 ] Add function mb_cache_entry_delete_or_get() to delete mbcache entry if it is unused and also add a function to wait for entry to become unused - mb_cache_entry_wait_unused(). We do not share code between the two deleting function as one of them will go away soon. CC: stable@vger.kernel.org Fixes: 82939d7999df ("ext4: convert to mbcache2") Signed-off-by: Jan Kara Link: https://lore.kernel.org/r/20220712105436.32204-2-jack@suse.cz Signed-off-by: Theodore Ts'o Stable-dep-of: a44e84a9b776 ("ext4: fix deadlock due to mbcache entry corruption") Signed-off-by: Sasha Levin --- fs/mbcache.c | 66 +++++++++++++++++++++++++++++++++++++++-- include/linux/mbcache.h | 10 ++++++- 2 files changed, 73 insertions(+), 3 deletions(-) diff --git a/fs/mbcache.c b/fs/mbcache.c index 12203e5a91e7..c76030e20d92 100644 --- a/fs/mbcache.c +++ b/fs/mbcache.c @@ -10,7 +10,7 @@ /* * Mbcache is a simple key-value store. Keys need not be unique, however * key-value pairs are expected to be unique (we use this fact in - * mb_cache_entry_delete()). + * mb_cache_entry_delete_or_get()). * * Ext2 and ext4 use this cache for deduplication of extended attribute blocks. * Ext4 also uses it for deduplication of xattr values stored in inodes. @@ -124,6 +124,19 @@ void __mb_cache_entry_free(struct mb_cache_entry *entry) } EXPORT_SYMBOL(__mb_cache_entry_free); +/* + * mb_cache_entry_wait_unused - wait to be the last user of the entry + * + * @entry - entry to work on + * + * Wait to be the last user of the entry. + */ +void mb_cache_entry_wait_unused(struct mb_cache_entry *entry) +{ + wait_var_event(&entry->e_refcnt, atomic_read(&entry->e_refcnt) <= 3); +} +EXPORT_SYMBOL(mb_cache_entry_wait_unused); + static struct mb_cache_entry *__entry_find(struct mb_cache *cache, struct mb_cache_entry *entry, u32 key) @@ -216,7 +229,7 @@ struct mb_cache_entry *mb_cache_entry_get(struct mb_cache *cache, u32 key, } EXPORT_SYMBOL(mb_cache_entry_get); -/* mb_cache_entry_delete - remove a cache entry +/* mb_cache_entry_delete - try to remove a cache entry * @cache - cache we work with * @key - key * @value - value @@ -253,6 +266,55 @@ void mb_cache_entry_delete(struct mb_cache *cache, u32 key, u64 value) } EXPORT_SYMBOL(mb_cache_entry_delete); +/* mb_cache_entry_delete_or_get - remove a cache entry if it has no users + * @cache - cache we work with + * @key - key + * @value - value + * + * Remove entry from cache @cache with key @key and value @value. The removal + * happens only if the entry is unused. The function returns NULL in case the + * entry was successfully removed or there's no entry in cache. Otherwise the + * function grabs reference of the entry that we failed to delete because it + * still has users and return it. + */ +struct mb_cache_entry *mb_cache_entry_delete_or_get(struct mb_cache *cache, + u32 key, u64 value) +{ + struct hlist_bl_node *node; + struct hlist_bl_head *head; + struct mb_cache_entry *entry; + + head = mb_cache_entry_head(cache, key); + hlist_bl_lock(head); + hlist_bl_for_each_entry(entry, node, head, e_hash_list) { + if (entry->e_key == key && entry->e_value == value) { + if (atomic_read(&entry->e_refcnt) > 2) { + atomic_inc(&entry->e_refcnt); + hlist_bl_unlock(head); + return entry; + } + /* We keep hash list reference to keep entry alive */ + hlist_bl_del_init(&entry->e_hash_list); + hlist_bl_unlock(head); + spin_lock(&cache->c_list_lock); + if (!list_empty(&entry->e_list)) { + list_del_init(&entry->e_list); + if (!WARN_ONCE(cache->c_entry_count == 0, + "mbcache: attempt to decrement c_entry_count past zero")) + cache->c_entry_count--; + atomic_dec(&entry->e_refcnt); + } + spin_unlock(&cache->c_list_lock); + mb_cache_entry_put(cache, entry); + return NULL; + } + } + hlist_bl_unlock(head); + + return NULL; +} +EXPORT_SYMBOL(mb_cache_entry_delete_or_get); + /* mb_cache_entry_touch - cache entry got used * @cache - cache the entry belongs to * @entry - entry that got used diff --git a/include/linux/mbcache.h b/include/linux/mbcache.h index 20f1e3ff6013..8eca7f25c432 100644 --- a/include/linux/mbcache.h +++ b/include/linux/mbcache.h @@ -30,15 +30,23 @@ void mb_cache_destroy(struct mb_cache *cache); int mb_cache_entry_create(struct mb_cache *cache, gfp_t mask, u32 key, u64 value, bool reusable); void __mb_cache_entry_free(struct mb_cache_entry *entry); +void mb_cache_entry_wait_unused(struct mb_cache_entry *entry); static inline int mb_cache_entry_put(struct mb_cache *cache, struct mb_cache_entry *entry) { - if (!atomic_dec_and_test(&entry->e_refcnt)) + unsigned int cnt = atomic_dec_return(&entry->e_refcnt); + + if (cnt > 0) { + if (cnt <= 3) + wake_up_var(&entry->e_refcnt); return 0; + } __mb_cache_entry_free(entry); return 1; } +struct mb_cache_entry *mb_cache_entry_delete_or_get(struct mb_cache *cache, + u32 key, u64 value); void mb_cache_entry_delete(struct mb_cache *cache, u32 key, u64 value); struct mb_cache_entry *mb_cache_entry_get(struct mb_cache *cache, u32 key, u64 value); -- 2.35.1