From: Eric Sandeen Subject: Re: [PATCH v2 2/2] [PATCH] xfs: Close race between direct IO and xfs_break_layouts() Date: Fri, 10 Aug 2018 13:31:57 -0500 Message-ID: References: <153374942137.42241.10539674028265137668.stgit@djiang5-desk3.ch.intel.com> Reply-To: sandeen-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: linux-nvdimm-hn68Rpc1hR1g9hUCZPvPmw@public.gmane.org, david-FqsqvQoI3Ljby3iVrkZq2A@public.gmane.org, linux-xfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, lczerner-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, linux-ext4-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, hch-jcswGhMUV9g@public.gmane.org To: Dave Jiang , tytso-3s7WtUTddSA@public.gmane.org, darrick.wong-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org, jack-AlSwsSmVLrQ@public.gmane.org, zwisler-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org Return-path: In-Reply-To: <153374942137.42241.10539674028265137668.stgit-Cxk7aZI4ujnJARH06PadV2t3HXsI98Cx0E9HWUfgJXw@public.gmane.org> Content-Language: en-US List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: linux-nvdimm-bounces-hn68Rpc1hR1g9hUCZPvPmw@public.gmane.org Sender: "Linux-nvdimm" List-Id: linux-ext4.vger.kernel.org On 8/8/18 12:31 PM, Dave Jiang wrote: > This patch is the duplicate of ross's fix for ext4 for xfs. > > If the refcount of a page is lowered between the time that it is returned > by dax_busy_page() and when the refcount is again checked in > xfs_break_layouts() => ___wait_var_event(), the waiting function > xfs_wait_dax_page() will never be called. This means that > xfs_break_layouts() will still have 'retry' set to false, so we'll stop > looping and never check the refcount of other pages in this inode. > > Instead, always continue looping as long as dax_layout_busy_page() gives us > a page which it found with an elevated refcount. Hi Dave, does this have a testcase? Have you seen the issue using Ross's xfstest generic/503 or is there some other test? Apologies if I missed prior discussion on a testcase or race frequency... Thanks, -Eric > Signed-off-by: Dave Jiang > Reviewed-by: Jan Kara > --- > > Sorry resend, forgot to add Jan's reviewed-by. > > v2: > - Rename parameter from did_unlock to retry (Jan) > > fs/xfs/xfs_file.c | 9 ++++----- > 1 file changed, 4 insertions(+), 5 deletions(-) > > diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c > index a3e7767a5715..cd6f0d8c4922 100644 > --- a/fs/xfs/xfs_file.c > +++ b/fs/xfs/xfs_file.c > @@ -721,12 +721,10 @@ xfs_file_write_iter( > > static void > xfs_wait_dax_page( > - struct inode *inode, > - bool *did_unlock) > + struct inode *inode) > { > struct xfs_inode *ip = XFS_I(inode); > > - *did_unlock = true; > xfs_iunlock(ip, XFS_MMAPLOCK_EXCL); > schedule(); > xfs_ilock(ip, XFS_MMAPLOCK_EXCL); > @@ -736,7 +734,7 @@ static int > xfs_break_dax_layouts( > struct inode *inode, > uint iolock, > - bool *did_unlock) > + bool *retry) > { > struct page *page; > > @@ -746,9 +744,10 @@ xfs_break_dax_layouts( > if (!page) > return 0; > > + *retry = true; > return ___wait_var_event(&page->_refcount, > atomic_read(&page->_refcount) == 1, TASK_INTERRUPTIBLE, > - 0, 0, xfs_wait_dax_page(inode, did_unlock)); > + 0, 0, xfs_wait_dax_page(inode)); > } > > int >