Merge tag 'scrub-fix-rtmeta-ilocking-6.2_2022-11-16' of...

Merge tag 'scrub-fix-rtmeta-ilocking-6.2_2022-11-16' of git://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfs-linux into xfs-6.2-mergeA

xfs: improve rt metadata use for scrub

This short series makes some small changes to the way we handle the
realtime metadata inodes.  First, we now make sure that the bitmap and
summary file forks are always loaded at mount time so that every
scrubber won't have to call xfs_iread_extents.  This won't be easy if
we're, say, cross-referencing realtime space allocations.  The second
change makes the ILOCK annotations more consistent with the rest of XFS.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>

* tag 'scrub-fix-rtmeta-ilocking-6.2_2022-11-16' of git://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfs-linux:
  xfs: make rtbitmap ILOCKing consistent when scanning the rt bitmap file
  xfs: load rtbitmap and rtsummary extent mapping btrees at mount time

fs/xfs/xfs_fsmap.c

@@ -524,7 +524,7 @@ xfs_getfsmap_rtdev_rtbitmap_query(
 	struct xfs_mount		*mp = tp->t_mountp;
 	int				error;
 
-	xfs_ilock(mp->m_rbmip, XFS_ILOCK_SHARED);
+	xfs_ilock(mp->m_rbmip, XFS_ILOCK_SHARED | XFS_ILOCK_RTBITMAP);
 
 	/*
 	 * Set up query parameters to return free rtextents covering the range
@@ -551,7 +551,7 @@ xfs_getfsmap_rtdev_rtbitmap_query(
 	if (error)
 		goto err;
 err:
-	xfs_iunlock(mp->m_rbmip, XFS_ILOCK_SHARED);
+	xfs_iunlock(mp->m_rbmip, XFS_ILOCK_SHARED | XFS_ILOCK_RTBITMAP);
 	return error;
 }
 

fs/xfs/xfs_rtalloc.c

@@ -1311,10 +1311,10 @@ xfs_rtalloc_reinit_frextents(
 	uint64_t		val = 0;
 	int			error;
 
-	xfs_ilock(mp->m_rbmip, XFS_ILOCK_EXCL);
+	xfs_ilock(mp->m_rbmip, XFS_ILOCK_SHARED | XFS_ILOCK_RTBITMAP);
 	error = xfs_rtalloc_query_all(mp, NULL, xfs_rtalloc_count_frextent,
 			&val);
-	xfs_iunlock(mp->m_rbmip, XFS_ILOCK_EXCL);
+	xfs_iunlock(mp->m_rbmip, XFS_ILOCK_SHARED | XFS_ILOCK_RTBITMAP);
 	if (error)
 		return error;
 
@@ -1325,6 +1325,41 @@ xfs_rtalloc_reinit_frextents(
 	return 0;
 }
 
+/*
+ * Read in the bmbt of an rt metadata inode so that we never have to load them
+ * at runtime.  This enables the use of shared ILOCKs for rtbitmap scans.  Use
+ * an empty transaction to avoid deadlocking on loops in the bmbt.
+ */
+static inline int
+xfs_rtmount_iread_extents(
+	struct xfs_inode	*ip,
+	unsigned int		lock_class)
+{
+	struct xfs_trans	*tp;
+	int			error;
+
+	error = xfs_trans_alloc_empty(ip->i_mount, &tp);
+	if (error)
+		return error;
+
+	xfs_ilock(ip, XFS_ILOCK_EXCL | lock_class);
+
+	error = xfs_iread_extents(tp, ip, XFS_DATA_FORK);
+	if (error)
+		goto out_unlock;
+
+	if (xfs_inode_has_attr_fork(ip)) {
+		error = xfs_iread_extents(tp, ip, XFS_ATTR_FORK);
+		if (error)
+			goto out_unlock;
+	}
+
+out_unlock:
+	xfs_iunlock(ip, XFS_ILOCK_EXCL | lock_class);
+	xfs_trans_cancel(tp);
+	return error;
+}
+
 /*
  * Get the bitmap and summary inodes and the summary cache into the mount
  * structure at mount time.
@@ -1342,14 +1377,27 @@ xfs_rtmount_inodes(
 		return error;
 	ASSERT(mp->m_rbmip != NULL);
 
+	error = xfs_rtmount_iread_extents(mp->m_rbmip, XFS_ILOCK_RTBITMAP);
+	if (error)
+		goto out_rele_bitmap;
+
 	error = xfs_iget(mp, NULL, sbp->sb_rsumino, 0, 0, &mp->m_rsumip);
-	if (error) {
-		xfs_irele(mp->m_rbmip);
-		return error;
-	}
+	if (error)
+		goto out_rele_bitmap;
 	ASSERT(mp->m_rsumip != NULL);
+
+	error = xfs_rtmount_iread_extents(mp->m_rsumip, XFS_ILOCK_RTSUM);
+	if (error)
+		goto out_rele_summary;
+
 	xfs_alloc_rsum_cache(mp, sbp->sb_rbmblocks);
 	return 0;
+
+out_rele_summary:
+	xfs_irele(mp->m_rsumip);
+out_rele_bitmap:
+	xfs_irele(mp->m_rbmip);
+	return error;
 }
 
 void