1 files changed, 263 insertions, 0 deletions
diff --git a/fs/xfs/xfs_zone_space_resv.c b/fs/xfs/xfs_zone_space_resv.c
new file mode 100644
index 000000000000..93c9a7721139
--- /dev/null
+++ b/fs/xfs/xfs_zone_space_resv.c
@@ -0,0 +1,263 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2023-2025 Christoph Hellwig.
+ * Copyright (c) 2024-2025, Western Digital Corporation or its affiliates.
+ */
+#include "xfs.h"
+#include "xfs_shared.h"
+#include "xfs_format.h"
+#include "xfs_trans_resv.h"
+#include "xfs_mount.h"
+#include "xfs_inode.h"
+#include "xfs_rtbitmap.h"
+#include "xfs_zone_alloc.h"
+#include "xfs_zone_priv.h"
+#include "xfs_zones.h"
+
+/*
+ * Note: the zoned allocator does not support a rtextsize > 1, so this code and
+ * the allocator itself uses file system blocks interchangeable with realtime
+ * extents without doing the otherwise required conversions.
+ */
+
+/*
+ * Per-task space reservation.
+ *
+ * Tasks that need to wait for GC to free up space allocate one of these
+ * on-stack and adds it to the per-mount zi_reclaim_reservations lists.
+ * The GC thread will then wake the tasks in order when space becomes available.
+ */
+struct xfs_zone_reservation {
+	struct list_head	entry;
+	struct task_struct	*task;
+	xfs_filblks_t		count_fsb;
+};
+
+/*
+ * Calculate the number of reserved blocks.
+ *
+ * XC_FREE_RTEXTENTS counts the user available capacity, to which the file
+ * system can be filled, while XC_FREE_RTAVAILABLE counts the blocks instantly
+ * available for writes without waiting for GC.
+ *
+ * For XC_FREE_RTAVAILABLE only the smaller reservation required for GC and
+ * block zeroing is excluded from the user capacity, while XC_FREE_RTEXTENTS
+ * is further restricted by at least one zone as well as the optional
+ * persistently reserved blocks.  This allows the allocator to run more
+ * smoothly by not always triggering GC.
+ */
+uint64_t
+xfs_zoned_default_resblks(
+	struct xfs_mount	*mp,
+	enum xfs_free_counter	ctr)
+{
+	switch (ctr) {
+	case XC_FREE_RTEXTENTS:
+		return (uint64_t)XFS_RESERVED_ZONES *
+			mp->m_groups[XG_TYPE_RTG].blocks +
+			mp->m_sb.sb_rtreserved;
+	case XC_FREE_RTAVAILABLE:
+		return (uint64_t)XFS_GC_ZONES *
+			mp->m_groups[XG_TYPE_RTG].blocks;
+	default:
+		ASSERT(0);
+		return 0;
+	}
+}
+
+void
+xfs_zoned_resv_wake_all(
+	struct xfs_mount		*mp)
+{
+	struct xfs_zone_info		*zi = mp->m_zone_info;
+	struct xfs_zone_reservation	*reservation;
+
+	spin_lock(&zi->zi_reservation_lock);
+	list_for_each_entry(reservation, &zi->zi_reclaim_reservations, entry)
+		wake_up_process(reservation->task);
+	spin_unlock(&zi->zi_reservation_lock);
+}
+
+void
+xfs_zoned_add_available(
+	struct xfs_mount		*mp,
+	xfs_filblks_t			count_fsb)
+{
+	struct xfs_zone_info		*zi = mp->m_zone_info;
+	struct xfs_zone_reservation	*reservation;
+
+	if (list_empty_careful(&zi->zi_reclaim_reservations)) {
+		xfs_add_freecounter(mp, XC_FREE_RTAVAILABLE, count_fsb);
+		return;
+	}
+
+	spin_lock(&zi->zi_reservation_lock);
+	xfs_add_freecounter(mp, XC_FREE_RTAVAILABLE, count_fsb);
+	count_fsb = xfs_sum_freecounter(mp, XC_FREE_RTAVAILABLE);
+	list_for_each_entry(reservation, &zi->zi_reclaim_reservations, entry) {
+		if (reservation->count_fsb > count_fsb)
+			break;
+		wake_up_process(reservation->task);
+		count_fsb -= reservation->count_fsb;
+
+	}
+	spin_unlock(&zi->zi_reservation_lock);
+}
+
+static int
+xfs_zoned_space_wait_error(
+	struct xfs_mount		*mp)
+{
+	if (xfs_is_shutdown(mp))
+		return -EIO;
+	if (fatal_signal_pending(current))
+		return -EINTR;
+	return 0;
+}
+
+static int
+xfs_zoned_reserve_available(
+	struct xfs_inode		*ip,
+	xfs_filblks_t			count_fsb,
+	unsigned int			flags)
+{
+	struct xfs_mount		*mp = ip->i_mount;
+	struct xfs_zone_info		*zi = mp->m_zone_info;
+	struct xfs_zone_reservation	reservation = {
+		.task		= current,
+		.count_fsb	= count_fsb,
+	};
+	int				error;
+
+	/*
+	 * If there are no waiters, try to directly grab the available blocks
+	 * from the percpu counter.
+	 *
+	 * If the caller wants to dip into the reserved pool also bypass the
+	 * wait list.  This relies on the fact that we have a very graciously
+	 * sized reserved pool that always has enough space.  If the reserved
+	 * allocations fail we're in trouble.
+	 */
+	if (likely(list_empty_careful(&zi->zi_reclaim_reservations) ||
+	    (flags & XFS_ZR_RESERVED))) {
+		error = xfs_dec_freecounter(mp, XC_FREE_RTAVAILABLE, count_fsb,
+				flags & XFS_ZR_RESERVED);
+		if (error != -ENOSPC)
+			return error;
+	}
+
+	if (flags & XFS_ZR_NOWAIT)
+		return -EAGAIN;
+
+	spin_lock(&zi->zi_reservation_lock);
+	list_add_tail(&reservation.entry, &zi->zi_reclaim_reservations);
+	while ((error = xfs_zoned_space_wait_error(mp)) == 0) {
+		set_current_state(TASK_KILLABLE);
+
+		error = xfs_dec_freecounter(mp, XC_FREE_RTAVAILABLE, count_fsb,
+				flags & XFS_ZR_RESERVED);
+		if (error != -ENOSPC)
+			break;
+
+		/*
+		 * Make sure to start GC if it is not running already. As we
+		 * check the rtavailable count when filling up zones, GC is
+		 * normally already running at this point, but in some setups
+		 * with very few zones we may completely run out of non-
+		 * reserved blocks in between filling zones.
+		 */
+		if (!xfs_is_zonegc_running(mp))
+			wake_up_process(zi->zi_gc_thread);
+
+		/*
+		 * If there is no reclaimable group left and we aren't still
+		 * processing a pending GC request give up as we're fully out
+		 * of space.
+		 */
+		if (!xfs_group_marked(mp, XG_TYPE_RTG, XFS_RTG_RECLAIMABLE) &&
+		    !xfs_is_zonegc_running(mp))
+			break;
+
+		spin_unlock(&zi->zi_reservation_lock);
+		schedule();
+		spin_lock(&zi->zi_reservation_lock);
+	}
+	list_del(&reservation.entry);
+	spin_unlock(&zi->zi_reservation_lock);
+
+	__set_current_state(TASK_RUNNING);
+	return error;
+}
+
+/*
+ * Implement greedy space allocation for short writes by trying to grab all
+ * that is left after locking out other threads from trying to do the same.
+ *
+ * This isn't exactly optimal and can hopefully be replaced by a proper
+ * percpu_counter primitive one day.
+ */
+static int
+xfs_zoned_reserve_extents_greedy(
+	struct xfs_inode		*ip,
+	xfs_filblks_t			*count_fsb,
+	unsigned int			flags)
+{
+	struct xfs_mount		*mp = ip->i_mount;
+	struct xfs_zone_info		*zi = mp->m_zone_info;
+	s64				len = *count_fsb;
+	int				error = -ENOSPC;
+
+	spin_lock(&zi->zi_reservation_lock);
+	len = min(len, xfs_sum_freecounter(mp, XC_FREE_RTEXTENTS));
+	if (len > 0) {
+		*count_fsb = len;
+		error = xfs_dec_freecounter(mp, XC_FREE_RTEXTENTS, *count_fsb,
+				flags & XFS_ZR_RESERVED);
+	}
+	spin_unlock(&zi->zi_reservation_lock);
+	return error;
+}
+
+int
+xfs_zoned_space_reserve(
+	struct xfs_inode		*ip,
+	xfs_filblks_t			count_fsb,
+	unsigned int			flags,
+	struct xfs_zone_alloc_ctx	*ac)
+{
+	struct xfs_mount		*mp = ip->i_mount;
+	int				error;
+
+	ASSERT(ac->reserved_blocks == 0);
+	ASSERT(ac->open_zone == NULL);
+
+	error = xfs_dec_freecounter(mp, XC_FREE_RTEXTENTS, count_fsb,
+			flags & XFS_ZR_RESERVED);
+	if (error == -ENOSPC && (flags & XFS_ZR_GREEDY) && count_fsb > 1)
+		error = xfs_zoned_reserve_extents_greedy(ip, &count_fsb, flags);
+	if (error)
+		return error;
+
+	error = xfs_zoned_reserve_available(ip, count_fsb, flags);
+	if (error) {
+		xfs_add_freecounter(mp, XC_FREE_RTEXTENTS, count_fsb);
+		return error;
+	}
+	ac->reserved_blocks = count_fsb;
+	return 0;
+}
+
+void
+xfs_zoned_space_unreserve(
+	struct xfs_inode		*ip,
+	struct xfs_zone_alloc_ctx	*ac)
+{
+	if (ac->reserved_blocks > 0) {
+		struct xfs_mount	*mp = ip->i_mount;
+
+		xfs_zoned_add_available(mp, ac->reserved_blocks);
+		xfs_add_freecounter(mp, XC_FREE_RTEXTENTS, ac->reserved_blocks);
+	}
+	if (ac->open_zone)
+		xfs_open_zone_put(ac->open_zone);
+}