xfs: define the format of rt groups

Define the ondisk format of realtime group metadata, and a superblock
for realtime volumes.  rt supers are conditionally enabled by a
predicate function so that they can be disabled if we ever implement
zoned storage support for the realtime volume.

For rt group enabled file systems there is a separate bitmap and summary
file for each group and thus the number of bitmap and summary blocks
needs to be calculated differently.

Signed-off-by: Darrick J. Wong <[email protected]>
Reviewed-by: Christoph Hellwig <[email protected]>

1 files changed, 17 insertions, 3 deletions

diff --git a/fs/xfs/libxfs/xfs_rtbitmap.c b/fs/xfs/libxfs/xfs_rtbitmap.c
index 54079edfe10f..416bbcd92af2 100644
--- a/fs/xfs/libxfs/xfs_rtbitmap.c
+++ b/fs/xfs/libxfs/xfs_rtbitmap.c
@@ -1157,6 +1157,21 @@ xfs_rtbitmap_blockcount_len(
 	return howmany_64(rtextents, NBBY * mp->m_sb.sb_blocksize);
 }
 
+/* How many rt extents does each rtbitmap file track? */
+static inline xfs_rtbxlen_t
+xfs_rtbitmap_bitcount(
+	struct xfs_mount	*mp)
+{
+	if (!mp->m_sb.sb_rextents)
+		return 0;
+
+	/* rtgroup size can be nonzero even if rextents is zero */
+	if (xfs_has_rtgroups(mp))
+		return mp->m_sb.sb_rgextents;
+
+	return mp->m_sb.sb_rextents;
+}
+
 /*
  * Compute the number of rtbitmap blocks used for a given file system.
  */
@@ -1164,7 +1179,7 @@ xfs_filblks_t
 xfs_rtbitmap_blockcount(
 	struct xfs_mount	*mp)
 {
-	return xfs_rtbitmap_blockcount_len(mp, mp->m_sb.sb_rextents);
+	return xfs_rtbitmap_blockcount_len(mp, xfs_rtbitmap_bitcount(mp));
 }
 
 /*
@@ -1178,8 +1193,7 @@ xfs_rtsummary_blockcount(
 {
 	unsigned long long	rsumwords;
 
-	*rsumlevels = xfs_compute_rextslog(mp->m_sb.sb_rextents) + 1;
-
+	*rsumlevels = xfs_compute_rextslog(xfs_rtbitmap_bitcount(mp)) + 1;
 	rsumwords = xfs_rtbitmap_blockcount(mp) * (*rsumlevels);
 	return XFS_B_TO_FSB(mp, rsumwords << XFS_WORDLOG);
 }