Return-Path: Received: from linuxhacker.ru ([217.76.32.60]:48884 "EHLO fiona.linuxhacker.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752632AbcFGPhl convert rfc822-to-8bit (ORCPT ); Tue, 7 Jun 2016 11:37:41 -0400 From: Oleg Drokin Content-Type: text/plain; charset=us-ascii Subject: Files leak from nfsd in 4.7.1-rc1 (and more?) Date: Tue, 7 Jun 2016 11:37:32 -0400 Message-Id: <4EDA6CFD-1FE8-4FCA-ACCF-84250BE342CB@linuxhacker.ru> Cc: linux-nfs@vger.kernel.org, " Mailing List" To: "J. Bruce Fields" , Jeff Layton Mime-Version: 1.0 (Apple Message framework v1283) Sender: linux-nfs-owner@vger.kernel.org List-ID: Hello! I've been trying to better understand this problem I was having where sometimes a formerly NFS-exported mountpoint becomes unmountable (after nfsd stop). I finally traced it to a leaked filedescriptor that was allocated from nfsd4_open()->nfsd4_process_open2()->nfs4_get_vfs_file()->nfsd_open(). Also together with it we see leaked credentials allocated along the same path from fh_verify() and groups allocated from svcauth_unix_accept()->groups_alloc() that are presumably used by the credentials. Unfortunately I was not able to make total sense out of the state handling in nfsd, but it's clear that one of the file descriptors inside struct nfs4_file is lost. I added a patch like this (always a good idea, so surprised it was not there already): @@ -271,6 +274,9 @@ static void nfsd4_free_file_rcu(struct rcu_head *rcu) { struct nfs4_file *fp = container_of(rcu, struct nfs4_file, fi_rcu); + WARN_ON(fp->fi_fds[0]); + WARN_ON(fp->fi_fds[1]); + WARN_ON(fp->fi_fds[2]); kmem_cache_free(file_slab, fp); } And when the problem is hit, I am also triggering (Always this one which is fd[1]) [ 3588.143002] ------------[ cut here ]------------ [ 3588.143662] WARNING: CPU: 5 PID: 9 at /home/green/bk/linux/fs/nfsd/nfs4state.c:278 nfsd4_free_file_rcu+0x65/0x80 [nfsd] [ 3588.144947] Modules linked in: loop rpcsec_gss_krb5 joydev acpi_cpufreq tpm_tis i2c_piix4 tpm virtio_console pcspkr nfsd ttm drm_kms_helper syscopyarea sysfillrect sysimgblt fb_sys_fops drm floppy serio_raw virtio_blk [ 3588.147135] CPU: 5 PID: 9 Comm: rcuos/0 Not tainted 4.7.0-rc1-vm-nfs+ #120 [ 3588.153826] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011 [ 3588.153830] 0000000000000286 00000000e2d5ccdf ffff88011965bd50 ffffffff814a11a5 [ 3588.153832] 0000000000000000 0000000000000000 ffff88011965bd90 ffffffff8108806b [ 3588.153834] 0000011600000000 ffff8800c476a0b8 ffff8800c476a048 ffffffffc0110fc0 [ 3588.153834] Call Trace: [ 3588.153839] [] dump_stack+0x86/0xc1 [ 3588.153841] [] __warn+0xcb/0xf0 [ 3588.153852] [] ? trace_raw_output_fh_want_write+0x60/0x60 [nfsd] [ 3588.153853] [] warn_slowpath_null+0x1d/0x20 [ 3588.153859] [] nfsd4_free_file_rcu+0x65/0x80 [nfsd] [ 3588.153861] [] rcu_nocb_kthread+0x335/0x510 [ 3588.153862] [] ? rcu_nocb_kthread+0x27f/0x510 [ 3588.153863] [] ? rcu_cpu_notify+0x3e0/0x3e0 [ 3588.153866] [] kthread+0x101/0x120 [ 3588.153868] [] ? trace_hardirqs_on_caller+0xf4/0x1b0 [ 3588.153871] [] ret_from_fork+0x1f/0x40 [ 3588.153872] [] ? kthread_create_on_node+0x250/0x250 release_all_access() seems to be doing correct job of all that cleaning, so there must be some other path that I do not quite see. Hopefully you are more familiar with the code and can see the problem right away ;) Bye, Oleg