Merge tag 'realtime-groups-6.13_2024-11-05' of https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfs-linux into staging-merge

xfs: shard the realtime section [v5.5 06/10]

Right now, the realtime section uses a single pair of metadata inodes to
store the free space information.  This presents a scalability problem
since every thread trying to allocate or free rt extents have to lock
these files.  Solve this problem by sharding the realtime section into
separate realtime allocation groups.

While we're at it, define a superblock to be stamped into the start of
the rt section.  This enables utilities such as blkid to identify block
devices containing realtime sections, and avoids the situation where
anything written into block 0 of the realtime extent can be
misinterpreted as file data.

The best advantage for rtgroups will become evident later when we get to
adding rmap and reflink to the realtime volume, since the geometry
constraints are the same for rt groups and AGs.  Hence we can reuse all
that code directly.

This is a very large patchset, but it catches us up with 20 years of
technical debt that have accumulated.

With a bit of luck, this should all go splendidly.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>

1 files changed, 20 insertions, 5 deletions

diff --git a/fs/xfs/xfs_trans_buf.c b/fs/xfs/xfs_trans_buf.c
index e28ab74af4f0..8e886ecfd69a 100644
--- a/fs/xfs/xfs_trans_buf.c
+++ b/fs/xfs/xfs_trans_buf.c
@@ -168,12 +168,11 @@ xfs_trans_get_buf_map(
 /*
  * Get and lock the superblock buffer for the given transaction.
  */
-struct xfs_buf *
-xfs_trans_getsb(
-	struct xfs_trans	*tp)
+static struct xfs_buf *
+__xfs_trans_getsb(
+	struct xfs_trans	*tp,
+	struct xfs_buf		*bp)
 {
-	struct xfs_buf		*bp = tp->t_mountp->m_sb_bp;
-
 	/*
 	 * Just increment the lock recursion count if the buffer is already
 	 * attached to this transaction.
@@ -197,6 +196,22 @@ xfs_trans_getsb(
 	return bp;
 }
 
+struct xfs_buf *
+xfs_trans_getsb(
+	struct xfs_trans	*tp)
+{
+	return __xfs_trans_getsb(tp, tp->t_mountp->m_sb_bp);
+}
+
+struct xfs_buf *
+xfs_trans_getrtsb(
+	struct xfs_trans	*tp)
+{
+	if (!tp->t_mountp->m_rtsb_bp)
+		return NULL;
+	return __xfs_trans_getsb(tp, tp->t_mountp->m_rtsb_bp);
+}
+
 /*
  * Get and lock the buffer for the caller if it is not already
  * locked within the given transaction.  If it has not yet been