Merge tag 'xfs-zoned-allocator-2025-03-03' of git://git.infradead.org/users/hch/xfs into xfs-6.15-zoned_devices

xfs: add support for zoned devices

Add support for the new zoned space allocator and thus for zoned devices:

    https://zonedstorage.io/docs/introduction/zoned-storage

to XFS. This has been developed for and tested on both SMR hard drives,
which are the oldest and most common class of zoned devices:

   https://zonedstorage.io/docs/introduction/smr

and ZNS SSDs:

   https://zonedstorage.io/docs/introduction/zns

It has not been tested with zoned UFS devices, as their current capacity
points and performance characteristics aren't too interesting for XFS
use cases (but never say never).

Sequential write only zones are only supported for data using a new
allocator for the RT device, which maps each zone to a rtgroup which
is written sequentially.  All metadata and (for now) the log require
using randomly writable space. This means a realtime device is required
to support zoned storage, but for the common case of SMR hard drives
that contain random writable zones and sequential write required zones
on the same block device, the concept of an internal RT device is added
which means using XFS on a SMR HDD is as simple as:

$ mkfs.xfs /dev/sda
$ mount /dev/sda /mnt

When using NVMe ZNS SSDs that do not support conventional zones, the
traditional multi-device RT configuration is required.  E.g. for an
SSD with a conventional namespace 1 and a zoned namespace 2:

$ mkfs.xfs /dev/nvme0n1 -o rtdev=/dev/nvme0n2
$ mount -o rtdev=/dev/nvme0n2 /dev/nvme0n1 /mnt

The zoned allocator can also be used on conventional block devices, or
on conventional zones (e.g. when using an SMR HDD as the external RT
device).  For example using zoned XFS on normal SSDs shows very nice
performance advantages and write amplification reduction for intelligent
workloads like RocksDB.

Some work is still in progress or planned, but should not affect the
integration with the rest of XFS or the on-disk format:

 - support for quotas
 - support for reflinks

Note that the I/O path already supports reflink, but garbage collection
isn't refcount aware yet and would unshare shared blocks, thus rendering
the feature useless.

1 files changed, 70 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..ecf39106704c
--- /dev/null
+++ b/fs/xfs/xfs_zone_alloc.h
@@ -0,0 +1,70 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _XFS_ZONE_ALLOC_H
+#define _XFS_ZONE_ALLOC_H
+
+struct iomap_ioend;
+struct xfs_open_zone;
+
+struct xfs_zone_alloc_ctx {
+	struct xfs_open_zone	*open_zone;
+	xfs_filblks_t		reserved_blocks;
+};
+
+/*
+ * Grab any available space, even if it is less than what the caller asked for.
+ */
+#define XFS_ZR_GREEDY		(1U << 0)
+/*
+ * Only grab instantly available space, don't wait or GC.
+ */
+#define XFS_ZR_NOWAIT		(1U << 1)
+/*
+ * Dip into the reserved pool.
+ */
+#define XFS_ZR_RESERVED		(1U << 2)
+
+int xfs_zoned_space_reserve(struct xfs_inode *ip, xfs_filblks_t count_fsb,
+		unsigned int flags, struct xfs_zone_alloc_ctx *ac);
+void xfs_zoned_space_unreserve(struct xfs_inode *ip,
+		struct xfs_zone_alloc_ctx *ac);
+void xfs_zoned_add_available(struct xfs_mount *mp, xfs_filblks_t count_fsb);
+
+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);
+
+uint64_t xfs_zoned_default_resblks(struct xfs_mount *mp,
+		enum xfs_free_counter ctr);
+void xfs_zoned_show_stats(struct seq_file *m, struct xfs_mount *mp);
+
+#ifdef CONFIG_XFS_RT
+int xfs_mount_zones(struct xfs_mount *mp);
+void xfs_unmount_zones(struct xfs_mount *mp);
+void xfs_zone_gc_start(struct xfs_mount *mp);
+void xfs_zone_gc_stop(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)
+{
+}
+static inline void xfs_zone_gc_start(struct xfs_mount *mp)
+{
+}
+static inline void xfs_zone_gc_stop(struct xfs_mount *mp)
+{
+}
+#endif /* CONFIG_XFS_RT */
+
+#endif /* _XFS_ZONE_ALLOC_H */