On Tue, May 15, 2018 at 05:41:29PM -0700, Darrick J. Wong wrote:
> On Wed, May 16, 2018 at 10:23:46AM +1000, Dave Chinner wrote:
> > On Tue, May 15, 2018 at 04:36:56PM -0700, Darrick J. Wong wrote:
> > > On Wed, May 16, 2018 at 09:08:11AM +1000, Dave Chinner wrote:
> > > > On Tue, May 15, 2018 at 01:47:21PM -0700, Darrick J. Wong wrote:
> > > > > From: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
> > > > >
> > > > > Use the new helper to read secondary superblocks instead of opencoding
> > > > > it ourselves.
> > > > >
> > > > > Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
> > > > > ---
> > > > > fs/xfs/xfs_fsops.c | 10 ++++------
> > > > > 1 file changed, 4 insertions(+), 6 deletions(-)
> > > > >
> > > > > diff --git a/fs/xfs/xfs_fsops.c b/fs/xfs/xfs_fsops.c
> > > > > index 056a76689197..40c131ebf772 100644
> > > > > --- a/fs/xfs/xfs_fsops.c
> > > > > +++ b/fs/xfs/xfs_fsops.c
> > > > > @@ -191,18 +191,15 @@ xfs_growfs_data_private(
> > > > > */
> > > > > int
> > > > > xfs_update_secondary_supers(
> > > > > - xfs_mount_t *mp)
> > > > > + struct xfs_mount *mp)
> > > > > {
> > > > > - int error, saved_error;
> > > > > + struct xfs_buf *bp;
> > > > > xfs_agnumber_t agno;
> > > > > - xfs_buf_t *bp;
> > > > > + int error, saved_error;
> > > > >
> > > > > error = saved_error = 0;
> > > > >
> > > > > for (agno = 1; agno < mp->m_sb.sb_agcount; agno++) {
> > > > > - error = xfs_trans_read_buf(mp, NULL, mp->m_ddev_targp,
> > > > > - XFS_AGB_TO_DADDR(mp, agno, XFS_SB_BLOCK(mp)),
> > > > > - XFS_FSS_TO_BB(mp, 1), 0, &bp, &xfs_sb_buf_ops);
> > > > > /*
> > > > > * If we get an error reading or writing alternate superblocks,
> > > > > * continue. xfs_repair chooses the "best" superblock based
> > > > > @@ -210,6 +207,7 @@ xfs_update_secondary_supers(
> > > > > * superblocks un-updated than updated, and xfs_repair may
> > > > > * pick them over the properly-updated primary.
> > > > > */
> > > > > + error = xfs_sb_read_secondary(mp, NULL, agno, &bp);
> > > > > if (error) {
> > > > > xfs_warn(mp,
> > > > > "error %d reading secondary superblock for ag %d",
> > > >
> > > > Why change this now when my growfs patchset ireworks it and then
> > > > moves the function entirely? Doing this now just breaks that
> > > > patchset unnecessarily and forces another rebase - can we move this
> > > > to the end of the growfs patchset?
> > >
> > > The label stuff will come after your growfs stuff... maybe I'll try this
> > > again tomorrow when I'm more awake.
> >
> > *nod*
>
> Aha, just s/xfs_update_secondary_supers/xfs_update_secondary_sbs/ in
> Eric's online label patch, and drop the one where he adds
> xfs_update_secondary_supers.
>
> > > Scrub wants a function to read a secondary sb, and a second one to clone
> > > the primary to fix damage by getting the sb, formatting the incore sb
> > > into the buffer, and writing it to disk.
> >
> > This is all done in a transaction context during scrub, isn't it?
> > Which means it's mostly separate to the non-transactional "update
> > all secondary SB's?
>
> Yes. It's likely we only want to update a single secondary sb, and
> updating all of them is overkill, so maybe it's fine just to open code
> this one use? Seeing as I don't think we'd ordinarily be updating only
> a single secondary sb.
Ok, so that means - initially, at least - they will be separate
functions.
In time, I'd like to explore making the secondary superblock
updates ordered buffers attached to a special superblock update
transaction (i.e. like the inode extent swap intent in the inode log
item flags), and that would probably allow us to factor it all down
to a single set of transaction aware functions...
> > > Label wants a function to read each secondary sb, format the incore sb
> > > into the buffer, and write it to disk.
> >
> > Yup - it can just use the function I added to rewrite all the
> > secondary superblocks.
> >
> > Hmmmm - just a thought here: does repair check and repair
> > inconsistent labels across secondary superblocks? What about UUID
> > updates? Do we have a generic need for some superblock updates to be
> > atomic across all superblocks?
>
> Online fsck checks both sb_fname and sb_uuid and complains if the
> secondaries are out of date. xfs_repair doesn't check at all.
OK, so I'm guessing that will get added to the growing list of
things that repair needs to check?
> > > Growfs wants to (read an existing ag's secondary sb | get a new ag's
> > > sb), format the incore sb into the buffer, and write it to disk.
> >
> > After my changes, growfs no longer reads the secondary superblocks.
> > It just rewrites them all completely by rewriting the primary SB
> > into them. The existing code rewrites them completely, too, so the
> > read is actually redundant and, potentially, can cause the grow to
> > fail.
>
> Ok, I had wondered myself if we should unconditionally rewrite the
> secondary sbs, because why would we care what the previous contents
> were?
Exactly :)
Cheers,
Dave.
--
Dave Chinner
david@xxxxxxxxxxxxx
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