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, 11 insertions, 1 deletions

diff --git a/fs/xfs/libxfs/xfs_alloc.h b/fs/xfs/libxfs/xfs_alloc.h
index efbde04fbbb1..50ef79a1ed41 100644
--- a/fs/xfs/libxfs/xfs_alloc.h
+++ b/fs/xfs/libxfs/xfs_alloc.h
@@ -237,7 +237,11 @@ int xfs_free_extent_later(struct xfs_trans *tp, xfs_fsblock_t bno,
 /* Don't issue a discard for the blocks freed. */
 #define XFS_FREE_EXTENT_SKIP_DISCARD	(1U << 0)
 
-#define XFS_FREE_EXTENT_ALL_FLAGS	(XFS_FREE_EXTENT_SKIP_DISCARD)
+/* Free blocks on the realtime device. */
+#define XFS_FREE_EXTENT_REALTIME	(1U << 1)
+
+#define XFS_FREE_EXTENT_ALL_FLAGS	(XFS_FREE_EXTENT_SKIP_DISCARD | \
+					 XFS_FREE_EXTENT_REALTIME)
 
 /*
  * List of extents to be free "later".
@@ -257,6 +261,12 @@ struct xfs_extent_free_item {
 #define XFS_EFI_ATTR_FORK	(1U << 1) /* freeing attr fork block */
 #define XFS_EFI_BMBT_BLOCK	(1U << 2) /* freeing bmap btree block */
 #define XFS_EFI_CANCELLED	(1U << 3) /* dont actually free the space */
+#define XFS_EFI_REALTIME	(1U << 4) /* freeing realtime extent */
+
+static inline bool xfs_efi_is_realtime(const struct xfs_extent_free_item *xefi)
+{
+	return xefi->xefi_flags & XFS_EFI_REALTIME;
+}
 
 struct xfs_alloc_autoreap {
 	struct xfs_defer_pending	*dfp;