From mboxrd@z Thu Jan 1 00:00:00 1970 From: Wu Fengguang Subject: Re: [RFC][PATCH v2] readahead: introduce O_RANDOM_READ for POSIX_FADV_RANDOM Date: Sat, 9 Jan 2010 21:59:04 +0800 Message-ID: <20100109135904.GA23944@localhost> References: <20091225000717.GA26949@yahoo-inc.com> <87aax18xms.fsf@basil.nowhere.org> <20091230051540.GA16308@localhost> <20091230052402.GB26364@localhost> <873a2s8hmp.fsf@basil.nowhere.org> <20091231043116.GA19397@localhost> <20100108130828.GA30480@infradead.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Andi Kleen , Andrew Morton , Quentin Barnes , "linux-kernel@vger.kernel.org" , "linux-fsdevel@vger.kernel.org" , Nick Piggin , Steven Whitehouse , David Howells , Al Viro , Jonathan Corbet To: Christoph Hellwig Return-path: Content-Disposition: inline In-Reply-To: <20100108130828.GA30480@infradead.org> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org On Fri, Jan 08, 2010 at 09:08:28PM +0800, Christoph Hellwig wrote: > Just thinking about this again, why don't you put the flag into > file->f_mode and the FMODE_* namespace given that we don't want it to be > settable from open? Good idea. To do that without race I would like to add ->f_lock to f_mode modifications at non-open time, like this. What do you think? --- vfs: take f_lock on modifying f_mode after open time Signed-off-by: Wu Fengguang --- fs/file_table.c | 2 ++ fs/nfsd/nfs4state.c | 2 ++ 2 files changed, 4 insertions(+) --- linux.orig/fs/file_table.c 2010-01-09 10:50:24.000000000 +0800 +++ linux/fs/file_table.c 2010-01-09 10:51:06.000000000 +0800 @@ -394,7 +394,9 @@ retry: continue; if (!(f->f_mode & FMODE_WRITE)) continue; + spin_lock(&f->f_lock); f->f_mode &= ~FMODE_WRITE; + spin_unlock(&f->f_lock); if (file_check_writeable(f) != 0) continue; file_release_write(f); --- linux.orig/fs/nfsd/nfs4state.c 2010-01-09 10:52:54.000000000 +0800 +++ linux/fs/nfsd/nfs4state.c 2010-01-09 10:52:56.000000000 +0800 @@ -1998,7 +1998,9 @@ nfs4_file_downgrade(struct file *filp, u { if (share_access & NFS4_SHARE_ACCESS_WRITE) { drop_file_write_access(filp); + spin_lock(&filp->f_lock); filp->f_mode = (filp->f_mode | FMODE_READ) & ~FMODE_WRITE; + spin_unlock(&filp->f_lock); } }