From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E40435335B8; Wed, 23 Sep 2026 14:55:16 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790175318; cv=none; b=bKROfTLd4tk/pTssLAfVpjEiy+5EB3J+7PbzTRAsKfDR7HDWdABh0xKCutP3Cxt53bTsrP/iDd4lnUM76YBhaSXYdMEzHKxI9KMQawNB/T50uOmf3XXcYWa3L/tBIiEfqOjOQ44SAnfeyOWCUdgyd3v9i0cN13R+Xs+jDDjzTPU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790175318; c=relaxed/simple; bh=pZ5ZtSHX+EyCvS/cy8vEconra8ZvemqLBUY/m/W1xSs=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=PZUQQLtaI+qk44lb60lKnDcXjLRNhD/pCA56EHlwTGzPrVdajp2ZD8w1ka8cV2zLLPFJuWIcabI8rm8ORGyWFyTFY4sNcY+huqDYGpMxANYTDThR0aIsZH2uMqgJUSV+F1IW4aJlCKmtTKm3QqNaCTQ+PDms85maIaVGHuH3Qw0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=hBjRGFhz; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="hBjRGFhz" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 074391F000FF; Wed, 23 Sep 2026 14:55:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1790175316; bh=FA707egiJkzTlbOagXg+OCMNnQNld899Jg1gw8Ytsts=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=hBjRGFhzhV/5Ohq2Q6nMlvdaMCIqjaULl8iScI5s9y+eQSKnw2ld1vt08kn1egEQi gvlDAf0tw/bQNcEpvs9qc91KTSmuCbx+MxavNsqUtouz2PMS4/xUUlYPIwFs1/ck+7 KxOt5wgEdHThcFQMiERYtsaTpBBR5LUoNHpSPc/c= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Zizhi Wo , Steve French , Hamza Mahfooz Subject: [PATCH 6.18 360/398] smb: client: fix busy dentry warning on unmount after DIO Date: Wed, 23 Sep 2026 16:07:14 +0200 Message-ID: <20260923140652.756908921@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260923140643.441954610@linuxfoundation.org> References: <20260923140643.441954610@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Zizhi Wo commit 75f5c412fa867efa0bf9b646bffe0d912109e84a upstream. Commit c68337442f03 ("cifs: Fix busy dentry used after unmounting") fixed the issue in cifs where deferred close of a file led to a dentry reference count not being released in umount, by flushing deferredclose_wq in cifs_kill_sb() to solve it. However, the cifs DIO path suffers from the same busy-dentry problem caused by a delayed dentry reference-count release: [dio] [cifsd] [close + umount] netfs_unbuffered_write_iter_locked ... cifs_demultiplex_thread netfs_unbuffered_write cifs_issue_write netfs_wait_for_in_progress_stream [1] ... netfs_write_subrequest_terminated netfs_subreq_clear_in_progress netfs_wake_collector // wake [1] netfs_put_subrequest netfs_put_request queue_work(system_dfl_wq, xxx) [2] // dio write return cifs_close _cifsFileInfo_put // cfile->count 2->1 --cfile->count [3] // umount cifs_kill_sb kill_anon_super // warning triggered! shrink_dcache_for_umount [4] [system_dfl_wq] [5] netfs_free_request ... _cifsFileInfo_put // cfile->count 1->0 --cfile->count queue_work(fileinfo_put_wq, xxx) [fileinfo_put_wq] [6] cifsFileInfo_put_work cifsFileInfo_put_final dput If the umount path is triggered before [5], it results warning: BUG: Dentry 00000000eab1f070{i=9a917b66ae404fec,n=test} still in use (1) [unmount of cifs cifs] The existing per-inode ictx->io_count wait in cifs_evict_inode() does not help: it lives in the inode eviction path, which runs after shrink_dcache_for_umount() has already warned about the busy dentries. Fix it by adding a per-superblock outstanding-rreq counter that is incremented in cifs_init_request() and decremented in cifs_free_request(). In cifs_kill_sb(), before kill_anon_super(), wait for this counter to reach 0 - which guarantees that all cleanup_work for this sb have run and thus all relevant cfile puts are queued on fileinfo_put_wq or serverclose_wq. Then drain the workqueue so the dentry refs are dropped. This is a targeted wait, not a flush of the system-wide system_dfl_wq. Fixes: 340cea84f691c ("cifs: open files should not hold ref on superblock") Signed-off-by: Zizhi Wo Signed-off-by: Steve French Signed-off-by: Hamza Mahfooz Signed-off-by: Greg Kroah-Hartman --- fs/smb/client/cifs_fs_sb.h | 1 + fs/smb/client/cifsfs.c | 12 ++++++++++++ fs/smb/client/connect.c | 1 + fs/smb/client/file.c | 5 +++++ 4 files changed, 19 insertions(+) --- a/fs/smb/client/cifs_fs_sb.h +++ b/fs/smb/client/cifs_fs_sb.h @@ -57,6 +57,7 @@ struct cifs_sb_info { struct smb3_fs_context *ctx; atomic_t active; atomic_t mnt_cifs_flags; + atomic_t outstanding_rreq; /* nr of rreqs not yet fully deinitialized */ struct delayed_work prune_tlinks; struct rcu_head rcu; --- a/fs/smb/client/cifsfs.c +++ b/fs/smb/client/cifsfs.c @@ -342,6 +342,18 @@ static void cifs_kill_sb(struct super_bl /* Wait for all opened files to release */ flush_workqueue(deferredclose_wq); + /* + * Wait for all in-flight netfs I/O requests to finish their + * cleanup_work so that any cifsFileInfo final puts they queue + * to fileinfo_put_wq/serverclose_wq have been queued, then + * drain the workqueue so the cfile dentry refs are dropped to + * avoid the busy dentry warning. + */ + wait_var_event(&cifs_sb->outstanding_rreq, + !atomic_read(&cifs_sb->outstanding_rreq)); + flush_workqueue(serverclose_wq); + flush_workqueue(fileinfo_put_wq); + /* finally release root dentry */ dput(cifs_sb->root); cifs_sb->root = NULL; --- a/fs/smb/client/connect.c +++ b/fs/smb/client/connect.c @@ -3597,6 +3597,7 @@ int cifs_setup_cifs_sb(struct cifs_sb_in spin_lock_init(&cifs_sb->tlink_tree_lock); cifs_sb->tlink_tree = RB_ROOT; + atomic_set(&cifs_sb->outstanding_rreq, 0); cifs_dbg(FYI, "file mode: %04ho dir mode: %04ho\n", ctx->file_mode, ctx->dir_mode); --- a/fs/smb/client/file.c +++ b/fs/smb/client/file.c @@ -289,6 +289,7 @@ static int cifs_init_request(struct netf return -EIO; } + atomic_inc(&cifs_sb->outstanding_rreq); return 0; } @@ -310,9 +311,13 @@ static void cifs_rreq_done(struct netfs_ static void cifs_free_request(struct netfs_io_request *rreq) { struct cifs_io_request *req = container_of(rreq, struct cifs_io_request, rreq); + struct cifs_sb_info *cifs_sb = CIFS_SB(rreq->inode->i_sb); if (req->cfile) cifsFileInfo_put(req->cfile); + + if (atomic_dec_and_test(&cifs_sb->outstanding_rreq)) + wake_up_var(&cifs_sb->outstanding_rreq); } static void cifs_free_subrequest(struct netfs_io_subrequest *subreq)