linux-kernel - Re: [PATCH] xfs: xfs_nfs_get_inode support zero generation

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Date:   Fri, 12 May 2023 12:00:09 +1000
From:   Dave Chinner <david@...morbit.com>
To:     "Darrick J. Wong" <djwong@...nel.org>
Cc:     renlei1@...natelecom.cn, linux-xfs@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] xfs: xfs_nfs_get_inode support zero generation

On Thu, May 11, 2023 at 04:22:06PM -0700, Darrick J. Wong wrote:
> On Thu, May 11, 2023 at 06:17:21PM +0800, renlei1@...natelecom.cn wrote:
> > From: Ren Lei <renlei1@...natelecom.cn>
> > 
> > If generation is zero, bypass the verification of generation number
> > to avoid stale file error. (Be consistent with other fs, such as
> > ext4, fat, jfs, etc.)
> 
> What code is affected by the gen==0 handles being rejected?  Is there a
> user program or test case where this is required?

A generation number of 0 is perfectly valid in XFS. We've been
creating them in XFS filesystems since 1993 and never had a problem
with filehandle verification. Indeed, every root inode in every XFS
filesystem ever made will have a generation number of 0.

Yup, a random XFS filesystem recently made from a current xfsprogs:

# xfs_db /dev/vdc
xfs_db> sb 0
xfs_db> a rootino
xfs_db> p core.gen
core.gen = 0
xfs_db> 

-Dave.
-- 
Dave Chinner
david@...morbit.com