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Message-ID: <20200618033333.py7dikfbu6sryzjd@gabell> Date: Wed, 17 Jun 2020 23:33:33 -0400 From: Masayoshi Mizuma <msys.mizuma@...il.com> To: "Darrick J. Wong" <darrick.wong@...cle.com> Cc: "J. Bruce Fields" <bfields@...ldses.org>, Eric Sandeen <sandeen@...deen.net>, Christoph Hellwig <hch@...radead.org>, Theodore Ts'o <tytso@....edu>, Andreas Dilger <adilger.kernel@...ger.ca>, Alexander Viro <viro@...iv.linux.org.uk>, Masayoshi Mizuma <m.mizuma@...fujitsu.com>, linux-ext4@...r.kernel.org, linux-fsdevel@...r.kernel.org, linux-xfs <linux-xfs@...r.kernel.org> Subject: Re: [PATCH] fs: i_version mntopt gets visible through /proc/mounts On Wed, Jun 17, 2020 at 06:44:29PM -0700, Darrick J. Wong wrote: > On Wed, Jun 17, 2020 at 09:30:26PM -0400, Masayoshi Mizuma wrote: > > On Wed, Jun 17, 2020 at 02:45:07PM -0400, J. Bruce Fields wrote: > > > On Wed, Jun 17, 2020 at 01:28:11PM -0500, Eric Sandeen wrote: > > > > but mount(8) has already exposed this interface: > > > > > > > > iversion > > > > Every time the inode is modified, the i_version field will be incremented. > > > > > > > > noiversion > > > > Do not increment the i_version inode field. > > > > > > > > so now what? > > > > > > It's not like anyone's actually depending on i_version *not* being > > > incremented. (Can you even observe it from userspace other than over > > > NFS?) > > > > > > So, just silently turn on the "iversion" behavior and ignore noiversion, > > > and I doubt you're going to break any real application. > > > > I suppose it's probably good to remain the options for user compatibility, > > however, it seems that iversion and noiversiont are useful for > > only ext4. > > How about moving iversion and noiversion description on mount(8) > > to ext4 specific option? > > > > And fixing the remount issue for XFS (maybe btrfs has the same > > issue as well)? > > For XFS like as: > > > > diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c > > index 379cbff438bc..2ddd634cfb0b 100644 > > --- a/fs/xfs/xfs_super.c > > +++ b/fs/xfs/xfs_super.c > > @@ -1748,6 +1748,9 @@ xfs_fc_reconfigure( > > return error; > > } > > > > + if (XFS_SB_VERSION_NUM(&mp->m_sb) == XFS_SB_VERSION_5) > > + mp->m_super->s_flags |= SB_I_VERSION; > > + > > I wonder, does this have to be done at the top of this function because > the vfs already removed S_I_VERSION from s_flags? Ah, I found the above code doesn't work... sb->s_flags will be updated after reconfigure(): int reconfigure_super(struct fs_context *fc) { ... if (fc->ops->reconfigure) { retval = fc->ops->reconfigure(fc); if (retval) { if (!force) goto cancel_readonly; /* If forced remount, go ahead despite any errors */ WARN(1, "forced remount of a %s fs returned %i\n", sb->s_type->name, retval); } } WRITE_ONCE(sb->s_flags, ((sb->s_flags & ~fc->sb_flags_mask) | (fc->sb_flags & fc->sb_flags_mask))); Here, fc->sb_flags_mask should be MS_RMT_MASK, so SB_I_VERSION will be dropped except iversion mount opstion (MS_I_VERSION) is set. - Masa
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