From: Christoph Hellwig <hch@lst.de>
Date: Mon, 14 Apr 2025 05:36:01 +0000 (+0200)
Subject: xfs: add the zoned space allocator
X-Git-Tag: v6.15.0~30
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=7681c8b64e8150667ea2d23e5134ffb5924b6607;p=thirdparty%2Fxfsprogs-dev.git

xfs: add the zoned space allocator

Source kernel commit: 4e4d52075577707f8393e3fc74c1ef79ca1d3ce6

For zoned RT devices space is always allocated at the write pointer, that
is right after the last written block and only recorded on I/O completion.

Because the actual allocation algorithm is very simple and just involves
picking a good zone - preferably the one used for the last write to the
inode.  As the number of zones that can written at the same time is
usually limited by the hardware, selecting a zone is done as late as
possible from the iomap dio and buffered writeback bio submissions
helpers just before submitting the bio.

Given that the writers already took a reservation before acquiring the
iolock, space will always be readily available if an open zone slot is
available.  A new structure is used to track these open zones, and
pointed to by the xfs_rtgroup.  Because zoned file systems don't have
a rsum cache the space for that pointer can be reused.

Allocations are only recorded at I/O completion time.  The scheme used
for that is very similar to the reflink COW end I/O path.

Co-developed-by: Hans Holmberg <hans.holmberg@wdc.com>
Signed-off-by: Hans Holmberg <hans.holmberg@wdc.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>
---

diff --git a/libxfs/xfs_rtgroup.h b/libxfs/xfs_rtgroup.h
index e35d1d79..5d8777f8 100644
--- a/libxfs/xfs_rtgroup.h
+++ b/libxfs/xfs_rtgroup.h
@@ -37,15 +37,27 @@ struct xfs_rtgroup {
 	xfs_rtxnum_t		rtg_extents;
 
 	/*
-	 * Cache of rt summary level per bitmap block with the invariant that
-	 * rtg_rsum_cache[bbno] > the maximum i for which rsum[i][bbno] != 0,
-	 * or 0 if rsum[i][bbno] == 0 for all i.
-	 *
+	 * For bitmap based RT devices this points to a cache of rt summary
+	 * level per bitmap block with the invariant that rtg_rsum_cache[bbno]
+	 * > the maximum i for which rsum[i][bbno] != 0, or 0 if
+	 * rsum[i][bbno] == 0 for all i.
 	 * Reads and writes are serialized by the rsumip inode lock.
+	 *
+	 * For zoned RT devices this points to the open zone structure for
+	 * a group that is open for writers, or is NULL.
 	 */
-	uint8_t			*rtg_rsum_cache;
+	union {
+		uint8_t			*rtg_rsum_cache;
+		struct xfs_open_zone	*rtg_open_zone;
+	};
 };
 
+/*
+ * For zoned RT devices this is set on groups that have no written blocks
+ * and can be picked by the allocator for opening.
+ */
+#define XFS_RTG_FREE			XA_MARK_0
+
 static inline struct xfs_rtgroup *to_rtg(struct xfs_group *xg)
 {
 	return container_of(xg, struct xfs_rtgroup, rtg_group);
diff --git a/libxfs/xfs_types.h b/libxfs/xfs_types.h
index 76f3c315..dc1db15f 100644
--- a/libxfs/xfs_types.h
+++ b/libxfs/xfs_types.h
@@ -243,6 +243,7 @@ enum xfs_free_counter {
 	 * Number of free RT extents on the RT device.
 	 */
 	XC_FREE_RTEXTENTS,
+
 	XC_FREE_NR,
 };