xfs: Move AGI buffer type setting to xfs_read_agi

We've missed properly setting the buffer type for
an AGI transaction in 3 spots now, so just move it
into xfs_read_agi() and set it if we are in a transaction
to avoid the problem in the future.

This is similar to how it is done in i.e. the dir3
and attr3 read functions.

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Dave Chinner <david@fromorbit.com>

diff --git a/fs/xfs/libxfs/xfs_ialloc.c b/fs/xfs/libxfs/xfs_ialloc.c
index 51b4e0d..c482b97 100644
--- a/fs/xfs/libxfs/xfs_ialloc.c
+++ b/fs/xfs/libxfs/xfs_ialloc.c
@@ -2450,8 +2450,6 @@
 	ASSERT(agi->agi_magicnum == cpu_to_be32(XFS_AGI_MAGIC));
 #endif
 
-	xfs_trans_buf_set_type(tp, bp, XFS_BLFT_AGI_BUF);
-
 	/*
 	 * Compute byte offsets for the first and last fields in the first
 	 * region and log the agi buffer. This only logs up through
@@ -2592,6 +2590,8 @@
 			XFS_FSS_TO_BB(mp, 1), 0, bpp, &xfs_agi_buf_ops);
 	if (error)
 		return error;
+	if (tp)
+		xfs_trans_buf_set_type(tp, *bpp, XFS_BLFT_AGI_BUF);
 
 	xfs_buf_set_ref(*bpp, XFS_AGI_REF);
 	return 0;