From patchwork Fri Apr 15 12:35:56 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jingbo Xu X-Patchwork-Id: 12814859 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 60914C4332F for ; Fri, 15 Apr 2022 12:36:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1353595AbiDOMjB (ORCPT ); Fri, 15 Apr 2022 08:39:01 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39548 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S245219AbiDOMiz (ORCPT ); Fri, 15 Apr 2022 08:38:55 -0400 Received: from out30-44.freemail.mail.aliyun.com (out30-44.freemail.mail.aliyun.com [115.124.30.44]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0FF4031DE6; Fri, 15 Apr 2022 05:36:24 -0700 (PDT) X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R121e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e04395;MF=jefflexu@linux.alibaba.com;NM=1;PH=DS;RN=19;SR=0;TI=SMTPD_---0VA7VPPx_1650026179; Received: from localhost(mailfrom:jefflexu@linux.alibaba.com fp:SMTPD_---0VA7VPPx_1650026179) by smtp.aliyun-inc.com(127.0.0.1); Fri, 15 Apr 2022 20:36:20 +0800 From: Jeffle Xu To: dhowells@redhat.com, linux-cachefs@redhat.com, xiang@kernel.org, chao@kernel.org, linux-erofs@lists.ozlabs.org Cc: torvalds@linux-foundation.org, gregkh@linuxfoundation.org, willy@infradead.org, linux-fsdevel@vger.kernel.org, joseph.qi@linux.alibaba.com, bo.liu@linux.alibaba.com, tao.peng@linux.alibaba.com, gerry@linux.alibaba.com, eguan@linux.alibaba.com, linux-kernel@vger.kernel.org, luodaowen.backend@bytedance.com, tianzichen@kuaishou.com, fannaihao@baidu.com, zhangjiachen.jaycee@bytedance.com Subject: [PATCH v9 03/21] cachefiles: unbind cachefiles gracefully in on-demand mode Date: Fri, 15 Apr 2022 20:35:56 +0800 Message-Id: <20220415123614.54024-4-jefflexu@linux.alibaba.com> X-Mailer: git-send-email 2.27.0 In-Reply-To: <20220415123614.54024-1-jefflexu@linux.alibaba.com> References: <20220415123614.54024-1-jefflexu@linux.alibaba.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org Add a refcount to avoid the deadlock in on-demand read mode. The on-demand read mode will pin the corresponding cachefiles object for each anonymous fd. The cachefiles object is unpinned when the anonymous fd gets closed. When the user daemon exits and the fd of "/dev/cachefiles" device node gets closed, it will wait for all cahcefiles objects gets withdrawn. Then if there's any anonymous fd getting closed after the fd of the device node, the user daemon will hang forever, waiting for all objects getting withdrawn. To fix this, add a refcount indicating if there's any object pinned by anonymous fds. The cachefiles cache gets unbound and withdrawn when the refcount decreased to 0. It won't change the behaviour of the original mode, in which case the cachefiles cache gets unbound and withdrawn as long as the fd of the device node gets closed. Besides, kref_get() is adequate whilst kref_get_unless_zero() is not needed here, since no more anonymous fd will be created when the .release() callback of the device node fd has already been called. Signed-off-by: Jeffle Xu --- fs/cachefiles/daemon.c | 24 +++++++++++++++++++++--- fs/cachefiles/internal.h | 3 +++ fs/cachefiles/ondemand.c | 3 +++ 3 files changed, 27 insertions(+), 3 deletions(-) diff --git a/fs/cachefiles/daemon.c b/fs/cachefiles/daemon.c index 69ca22aa6abf..2e946e4eb65a 100644 --- a/fs/cachefiles/daemon.c +++ b/fs/cachefiles/daemon.c @@ -111,6 +111,7 @@ static int cachefiles_daemon_open(struct inode *inode, struct file *file) INIT_LIST_HEAD(&cache->volumes); INIT_LIST_HEAD(&cache->object_list); spin_lock_init(&cache->object_list_lock); + kref_init(&cache->unbind_pincount); #ifdef CONFIG_CACHEFILES_ONDEMAND xa_init_flags(&cache->reqs, XA_FLAGS_ALLOC); xa_init_flags(&cache->ondemand_ids, XA_FLAGS_ALLOC1); @@ -157,6 +158,25 @@ static void cachefiles_flush_reqs(struct cachefiles_cache *cache) } #endif +static void cachefiles_release_cache(struct kref *kref) +{ + struct cachefiles_cache *cache; + + cache = container_of(kref, struct cachefiles_cache, unbind_pincount); + cachefiles_daemon_unbind(cache); + kfree(cache); +} + +void cachefiles_put_unbind_pincount(struct cachefiles_cache *cache) +{ + kref_put(&cache->unbind_pincount, cachefiles_release_cache); +} + +void cachefiles_get_unbind_pincount(struct cachefiles_cache *cache) +{ + kref_get(&cache->unbind_pincount); +} + /* * Release a cache. */ @@ -173,14 +193,12 @@ static int cachefiles_daemon_release(struct inode *inode, struct file *file) #ifdef CONFIG_CACHEFILES_ONDEMAND cachefiles_flush_reqs(cache); #endif - cachefiles_daemon_unbind(cache); - /* clean up the control file interface */ cache->cachefilesd = NULL; file->private_data = NULL; cachefiles_open = 0; - kfree(cache); + cachefiles_put_unbind_pincount(cache); _leave(""); return 0; diff --git a/fs/cachefiles/internal.h b/fs/cachefiles/internal.h index 8ebe238af20b..9b83d8c82709 100644 --- a/fs/cachefiles/internal.h +++ b/fs/cachefiles/internal.h @@ -109,6 +109,7 @@ struct cachefiles_cache { char *rootdirname; /* name of cache root directory */ char *secctx; /* LSM security context */ char *tag; /* cache binding tag */ + struct kref unbind_pincount;/* refcount to do daemon unbind */ #ifdef CONFIG_CACHEFILES_ONDEMAND struct xarray reqs; /* xarray of pending on-demand requests */ struct xarray ondemand_ids; /* xarray for ondemand_id allocation */ @@ -167,6 +168,8 @@ extern int cachefiles_has_space(struct cachefiles_cache *cache, * daemon.c */ extern const struct file_operations cachefiles_daemon_fops; +extern void cachefiles_get_unbind_pincount(struct cachefiles_cache *cache); +extern void cachefiles_put_unbind_pincount(struct cachefiles_cache *cache); /* * error_inject.c diff --git a/fs/cachefiles/ondemand.c b/fs/cachefiles/ondemand.c index 890cd3ecc2f0..eec883640efa 100644 --- a/fs/cachefiles/ondemand.c +++ b/fs/cachefiles/ondemand.c @@ -14,6 +14,7 @@ static int cachefiles_ondemand_fd_release(struct inode *inode, object->ondemand_id = CACHEFILES_ONDEMAND_ID_CLOSED; xa_erase(&cache->ondemand_ids, object_id); cachefiles_put_object(object, cachefiles_obj_put_ondemand_fd); + cachefiles_put_unbind_pincount(cache); return 0; } @@ -169,6 +170,8 @@ static int cachefiles_ondemand_get_fd(struct cachefiles_req *req) load->fd = fd; req->msg.object_id = object_id; object->ondemand_id = object_id; + + cachefiles_get_unbind_pincount(cache); return 0; err_put_fd: