On Thu, Apr 19, 2018 at 10:25:48AM -0700, Darrick J. Wong wrote:
> On Thu, Apr 19, 2018 at 08:55:47AM -0400, Brian Foster wrote:
> > On Tue, Apr 17, 2018 at 07:40:20PM -0700, Darrick J. Wong wrote:
> > > From: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
> > >
> > > We've never cached buffers when reading or writing superblocks, so we
> > > need to change scrub to do likewise or risk screwing up the uncached sb
> > > buffer usage everywhere else.
> > >
> > > Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
> > > ---
> >
> > Hmm, so this goes back to this[1] thread, right?
>
> Yep.
>
> > IIRC, we wanted to end up with an lru-bypassing uncached buffer lookup
> > mechanism to provide uncached behavior for resource-saving purposes
> > but without introducing serialization issues between multiple users of
> > uncached buffers.
>
> Right.
>
> > On a quick look back, growfs currently uses cached buffers for secondary
> > superblocks and the associated patch was looking to change that to
> > something like the above. Don't we have the same requirement here (since
> > growfs currently still uses cached buffers)?
>
> Correct, this patch is contingent on landing Dave's "tableise growfs"
> series that converts growfs to use uncached buffers for writing out the
> new secondary supers. If I manage to land Dave's growfs thing before
> repair then I'll keep this; if repair goes first I'll defer it to that
> series.
>
Ok, though I'm not sure I see the need for the higher level series
dependency. Don't one of these patches just need to fold in a helper[1]
to set the lru reference appropriately and start to use it?
Brian
[1] I.e., untested:
diff --git a/fs/xfs/libxfs/xfs_sb.c b/fs/xfs/libxfs/xfs_sb.c
index d9b94bd5f689..19ffe2819bb2 100644
--- a/fs/xfs/libxfs/xfs_sb.c
+++ b/fs/xfs/libxfs/xfs_sb.c
@@ -972,3 +972,24 @@ xfs_fs_geometry(
return 0;
}
+
+int
+xfs_read_secondary_sb(
+ struct xfs_mount *mp,
+ struct xfs_trans *tp,
+ xfs_agnumber_t agno,
+ struct xfs_buf **bpp)
+{
+ struct xfs_buf *bp;
+ int error;
+
+ ASSERT(agno != NULLAGNUMBER);
+ error = xfs_trans_read_buf(mp, tp, mp->m_ddev_targp,
+ XFS_AG_DADDR(mp, agno, XFS_SB_BLOCK(mp)),
+ XFS_FSS_TO_BB(mp, 1), 0, &bp, &xfs_sb_buf_ops);
+ if (error)
+ return error;
+ xfs_buf_set_ref(bp, XFS_SSB_REF);
+ *bpp = bp;
+ return 0;
+}
diff --git a/fs/xfs/libxfs/xfs_shared.h b/fs/xfs/libxfs/xfs_shared.h
index d0b84da0cb1e..d23f33c02f64 100644
--- a/fs/xfs/libxfs/xfs_shared.h
+++ b/fs/xfs/libxfs/xfs_shared.h
@@ -127,6 +127,7 @@ void xfs_log_get_max_trans_res(struct xfs_mount *mp,
#define XFS_ATTR_BTREE_REF 1
#define XFS_DQUOT_REF 1
#define XFS_REFC_BTREE_REF 1
+#define XFS_SSB_REF 0
/*
* Flags for xfs_trans_ichgtime().
--
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