From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from userp1040.oracle.com ([156.151.31.81]:37949 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752989AbdHKQAC (ORCPT ); Fri, 11 Aug 2017 12:00:02 -0400 Date: Fri, 11 Aug 2017 08:59:56 -0700 From: "Darrick J. Wong" Subject: Re: [PATCH] xfs: fix inobt inode allocation search optimization Message-ID: <20170811155956.GZ24087@magnolia> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: linux-xfs-owner@vger.kernel.org List-ID: List-Id: xfs To: Omar Sandoval Cc: linux-xfs@vger.kernel.org, kernel-team@fb.com On Thu, Aug 10, 2017 at 09:45:45PM -0700, Omar Sandoval wrote: Looks ok, will test... Reviewed-by: Darrick J. Wong --D > From: Omar Sandoval > > When we try to allocate a free inode by searching the inobt, we try to > find the inode nearest the parent inode by searching chunks both left > and right of the chunk containing the parent. As an optimization, we > cache the leftmost and rightmost records that we previously searched; if > we do another allocation with the same parent inode, we'll pick up the > search where it last left off. > > There's a bug in the case where we found a free inode to the left of the > parent's chunk: we need to update the cached left and right records, but > because we already reassigned the right record to point to the left, we > end up assigning the left record to both the cached left and right > records. > > This isn't a correctness problem strictly, but it can result in the next > allocation rechecking chunks unnecessarily or allocating inodes further > away from the parent than it needs to. Fix it by swapping the record > pointer after we update the cached left and right records. > > Fixes: bd169565993b ("xfs: speed up free inode search") > Signed-off-by: Omar Sandoval > --- > fs/xfs/libxfs/xfs_ialloc.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/fs/xfs/libxfs/xfs_ialloc.c b/fs/xfs/libxfs/xfs_ialloc.c > index ffd5a15d1bb6..abf5beaae907 100644 > --- a/fs/xfs/libxfs/xfs_ialloc.c > +++ b/fs/xfs/libxfs/xfs_ialloc.c > @@ -1246,13 +1246,13 @@ xfs_dialloc_ag_inobt( > > /* free inodes to the left? */ > if (useleft && trec.ir_freecount) { > - rec = trec; > xfs_btree_del_cursor(cur, XFS_BTREE_NOERROR); > cur = tcur; > > pag->pagl_leftrec = trec.ir_startino; > pag->pagl_rightrec = rec.ir_startino; > pag->pagl_pagino = pagino; > + rec = trec; > goto alloc_inode; > } > > -- > 2.14.0 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-xfs" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html