From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from relay.sgi.com (relay2.corp.sgi.com [137.38.102.29]) by oss.sgi.com (Postfix) with ESMTP id D4AC07F52 for ; Thu, 8 May 2014 17:05:27 -0500 (CDT) Received: from cuda.sgi.com (cuda1.sgi.com [192.48.157.11]) by relay2.corp.sgi.com (Postfix) with ESMTP id 9AC8C304051 for ; Thu, 8 May 2014 15:05:27 -0700 (PDT) Received: from ipmail06.adl2.internode.on.net (ipmail06.adl2.internode.on.net [150.101.137.129]) by cuda.sgi.com with ESMTP id LIvz3n8QkdVu35Pc for ; Thu, 08 May 2014 15:05:25 -0700 (PDT) Date: Fri, 9 May 2014 08:05:05 +1000 From: Dave Chinner Subject: Re: [PATCH] xfs: remove XFS_TRANS_RESERVE in collapse range Message-ID: <20140508220505.GG26353@dastard> References: <002601cf6aa2$c59cd670$50d68350$@samsung.com> <20140508133637.GB47272@bfoster.bfoster> <20140508211712.GD26353@dastard> <20140508215115.GA30141@laptop.bfoster> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20140508215115.GA30141@laptop.bfoster> List-Id: XFS Filesystem from SGI List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: xfs-bounces@oss.sgi.com Sender: xfs-bounces@oss.sgi.com To: Brian Foster Cc: Namjae Jeon , xfs@oss.sgi.com On Thu, May 08, 2014 at 05:51:16PM -0400, Brian Foster wrote: > On Fri, May 09, 2014 at 07:17:12AM +1000, Dave Chinner wrote: > > On Thu, May 08, 2014 at 09:36:37AM -0400, Brian Foster wrote: > > > On Thu, May 08, 2014 at 06:49:14PM +0900, Namjae Jeon wrote: > > > > There is no need to dip into reserve pool. Reserve pool is used for much > > > > more important things. And xfs_trans_reserve will never return ENOSPC > > > > because punch hole is already done. If we get ENOSPC, collapse range > > > > will be simply failed. > > > > > > > > Signed-off-by: Namjae Jeon > > > > Signed-off-by: Ashish Sangwan > > > > --- > > > > fs/xfs/xfs_bmap_util.c | 3 +-- > > > > 1 file changed, 1 insertion(+), 2 deletions(-) > > > > > > > > diff --git a/fs/xfs/xfs_bmap_util.c b/fs/xfs/xfs_bmap_util.c > > > > index 296160b..91a43c5 100644 > > > > --- a/fs/xfs/xfs_bmap_util.c > > > > +++ b/fs/xfs/xfs_bmap_util.c > > > > @@ -1519,7 +1519,6 @@ xfs_collapse_file_space( > > > > > > > > while (!error && !done) { > > > > tp = xfs_trans_alloc(mp, XFS_TRANS_DIOSTRAT); > > > > - tp->t_flags |= XFS_TRANS_RESERVE; > > > > > > Makes sense. > > > > > > > /* > > > > * We would need to reserve permanent block for transaction. > > > > * This will come into picture when after shifting extent into > > > > @@ -1529,7 +1528,7 @@ xfs_collapse_file_space( > > > > error = xfs_trans_reserve(tp, &M_RES(mp)->tr_write, > > > > XFS_DIOSTRAT_SPACE_RES(mp, 0), 0); > > > > if (error) { > > > > - ASSERT(error == ENOSPC || XFS_FORCED_SHUTDOWN(mp)); > > > > + ASSERT(XFS_FORCED_SHUTDOWN(mp)); > > > > > > The xfs_trans_reserve() call still reserves XFS_DIOSTRAT_SPACE_RES() > > > blocks, so therefore I think ENOSPC is still a possibility. The question > > > is probably whether or not we need to reserve blocks for this > > > transaction. > > > > > > Making a pass through the code... we have the possibility of deleting a > > > btree record in xfs_bmap_shift_extents(). This in turn could potentially > > > free a btree block, which frees space. I _think_ this could mean we > > > want to keep the block reservation because we update the free space > > > trees, but I suppose that could be handled by the freelist... > > > > > > Perhaps Dave can confirm which direction we should go here..? > > > > Having collapse range fail with ENOSPC is not an issue - it is being > > executed in a context where we can fail safely and return an error > > to the user. > > > > XFS_TRANS_RESERVE is used in places where a failure is unrecoverable > > or there is no one to report the error to. e.g. prevent data loss > > due to ENOSPC in unwritten extent conversion during background > > buffered write IO completion > > > > So here there is no need for it at all.... > > > > Yeah, dropping XFS_TRANS_RESERVE makes sense. The question I have is > whether we should reserve blocks for this transaction (for a potential > bmbt block free). If we do reserve blocks, then I assume the ENOSPC > assert should stick around. Yes, the assert is wrong because xfs_trans_reserve() can return ENOMEM as well as ENOSPC. It should just be removed. Cheers, Dave. -- Dave Chinner david@fromorbit.com _______________________________________________ xfs mailing list xfs@oss.sgi.com http://oss.sgi.com/mailman/listinfo/xfs