From patchwork Mon Apr 25 12:21:25 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jingbo Xu X-Patchwork-Id: 12825676 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 44FC2C433FE for ; Mon, 25 Apr 2022 12:22:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241768AbiDYMZS (ORCPT ); Mon, 25 Apr 2022 08:25:18 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60914 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236979AbiDYMY6 (ORCPT ); Mon, 25 Apr 2022 08:24:58 -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 CCA0160065; Mon, 25 Apr 2022 05:21:53 -0700 (PDT) X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R151e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e04400;MF=jefflexu@linux.alibaba.com;NM=1;PH=DS;RN=20;SR=0;TI=SMTPD_---0VBDlJDM_1650889308; Received: from localhost(mailfrom:jefflexu@linux.alibaba.com fp:SMTPD_---0VBDlJDM_1650889308) by smtp.aliyun-inc.com(127.0.0.1); Mon, 25 Apr 2022 20:21:50 +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, zhujia.zj@bytedance.com Subject: [PATCH v10 03/21] cachefiles: unbind cachefiles gracefully in on-demand mode Date: Mon, 25 Apr 2022 20:21:25 +0800 Message-Id: <20220425122143.56815-4-jefflexu@linux.alibaba.com> X-Mailer: git-send-email 2.27.0 In-Reply-To: <20220425122143.56815-1-jefflexu@linux.alibaba.com> References: <20220425122143.56815-1-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 getting 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 is 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. Signed-off-by: Jeffle Xu --- fs/cachefiles/daemon.c | 19 ++++++++++++++++--- fs/cachefiles/internal.h | 3 +++ fs/cachefiles/ondemand.c | 3 +++ 3 files changed, 22 insertions(+), 3 deletions(-) diff --git a/fs/cachefiles/daemon.c b/fs/cachefiles/daemon.c index d5417da7f792..5b1d0642c749 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); + refcount_set(&cache->unbind_pincount, 1); xa_init_flags(&cache->reqs, XA_FLAGS_ALLOC); xa_init_flags(&cache->ondemand_ids, XA_FLAGS_ALLOC1); @@ -164,6 +165,20 @@ static void cachefiles_flush_reqs(struct cachefiles_cache *cache) xa_destroy(&cache->ondemand_ids); } +void cachefiles_put_unbind_pincount(struct cachefiles_cache *cache) +{ + if (refcount_dec_and_test(&cache->unbind_pincount)) { + cachefiles_daemon_unbind(cache); + cachefiles_open = 0; + kfree(cache); + } +} + +void cachefiles_get_unbind_pincount(struct cachefiles_cache *cache) +{ + refcount_inc(&cache->unbind_pincount); +} + /* * Release a cache. */ @@ -179,14 +194,12 @@ static int cachefiles_daemon_release(struct inode *inode, struct file *file) if (cachefiles_in_ondemand_mode(cache)) cachefiles_flush_reqs(cache); - 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 4f5150a96849..e5c612888f84 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 */ + refcount_t unbind_pincount;/* refcount to do daemon unbind */ struct xarray reqs; /* xarray of pending on-demand requests */ struct xarray ondemand_ids; /* xarray for ondemand_id allocation */ u32 ondemand_id_next; @@ -171,6 +172,8 @@ 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 64fc312b16d3..7946ee6c40be 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: