Return-Path: Received: from m12-12.163.com ([220.181.12.12]:42775 "EHLO m12-12.163.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751657AbdFEMe0 (ORCPT ); Mon, 5 Jun 2017 08:34:26 -0400 Message-ID: <5935505B.8050009@163.com> Date: Mon, 05 Jun 2017 20:36:43 +0800 From: Jia-Ju Bai MIME-Version: 1.0 To: Trond Myklebust CC: "anna.schumaker@netapp.com" , "linux-kernel@vger.kernel.org" , "linux-nfs@vger.kernel.org" Subject: Re: [PATCH] fs: nfs: Fix a sleep-in-atomic bug in nfs_access_add_cache References: <1496649904-1855-1-git-send-email-baijiaju1990@163.com> <1496663315.3433.1.camel@primarydata.com> In-Reply-To: <1496663315.3433.1.camel@primarydata.com> Content-Type: text/plain; charset=UTF-8; format=flowed Sender: linux-nfs-owner@vger.kernel.org List-ID: On 06/05/2017 07:48 PM, Trond Myklebust wrote: > On Mon, 2017-06-05 at 16:05 +0800, Jia-Ju Bai wrote: >> The driver may sleep under a rcu read lock, and function call path >> is: >> nfs_permission (acquire the lock by rcu_read_lock) >> nfs_do_access >> nfs_access_add_cache >> kmalloc(GFP_KERNEL) --> may sleep >> >> To fix it, "GFP_KERNEL" is replaced with "GFP_ATOMIC". >> >> Signed-off-by: Jia-Ju Bai >> --- >> fs/nfs/dir.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c >> index 32ccd77..7a074db 100644 >> --- a/fs/nfs/dir.c >> +++ b/fs/nfs/dir.c >> @@ -2333,7 +2333,7 @@ static void nfs_access_add_rbtree(struct inode >> *inode, struct nfs_access_entry * >> >> void nfs_access_add_cache(struct inode *inode, struct >> nfs_access_entry *set) >> { >> - struct nfs_access_entry *cache = kmalloc(sizeof(*cache), >> GFP_KERNEL); >> + struct nfs_access_entry *cache = kmalloc(sizeof(*cache), >> GFP_ATOMIC); >> if (cache == NULL) >> return; >> RB_CLEAR_NODE(&cache->rb_node); > The RCU locked codepath will not ever hit nfs_access_add_rbtree(). It > returns with an error code of -ECHILD after the test of "may_block". > > Cheers > Trond Yes, I think you are right. Thanks, Jia-Ju Bai