xfs: add the zoned space allocator

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>

1 files changed, 34 insertions, 0 deletions

diff --git a/fs/xfs/xfs_zone_alloc.h b/fs/xfs/xfs_zone_alloc.h
new file mode 100644
index 000000000000..78cd7bfc6ac8
--- /dev/null
+++ b/fs/xfs/xfs_zone_alloc.h
@@ -0,0 +1,34 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _XFS_ZONE_ALLOC_H
+#define _XFS_ZONE_ALLOC_H
+
+struct iomap_ioend;
+struct xfs_open_zone;
+
+void xfs_zone_alloc_and_submit(struct iomap_ioend *ioend,
+		struct xfs_open_zone **oz);
+int xfs_zone_free_blocks(struct xfs_trans *tp, struct xfs_rtgroup *rtg,
+		xfs_fsblock_t fsbno, xfs_filblks_t len);
+int xfs_zoned_end_io(struct xfs_inode *ip, xfs_off_t offset, xfs_off_t count,
+		xfs_daddr_t daddr, struct xfs_open_zone *oz,
+		xfs_fsblock_t old_startblock);
+void xfs_open_zone_put(struct xfs_open_zone *oz);
+
+void xfs_zoned_wake_all(struct xfs_mount *mp);
+bool xfs_zone_rgbno_is_valid(struct xfs_rtgroup *rtg, xfs_rgnumber_t rgbno);
+void xfs_mark_rtg_boundary(struct iomap_ioend *ioend);
+
+#ifdef CONFIG_XFS_RT
+int xfs_mount_zones(struct xfs_mount *mp);
+void xfs_unmount_zones(struct xfs_mount *mp);
+#else
+static inline int xfs_mount_zones(struct xfs_mount *mp)
+{
+	return -EIO;
+}
+static inline void xfs_unmount_zones(struct xfs_mount *mp)
+{
+}
+#endif /* CONFIG_XFS_RT */
+
+#endif /* _XFS_ZONE_ALLOC_H */