1 files changed, 96 insertions, 0 deletions
diff --git a/include/uapi/linux/fsrefcounts.h b/include/uapi/linux/fsrefcounts.h
new file mode 100644
index 000000000000..f18752edfbee
--- /dev/null
+++ b/include/uapi/linux/fsrefcounts.h
@@ -0,0 +1,96 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+/*
+ * FS_IOC_GETFSREFCOUNTS ioctl infrastructure.
+ *
+ * Copyright (C) 2021 Oracle.  All Rights Reserved.
+ *
+ * Author: Darrick J. Wong <djwong@kernel.org>
+ */
+#ifndef _LINUX_FSREFCOUNTS_H
+#define _LINUX_FSREFCOUNTS_H
+
+#include <linux/types.h>
+
+/*
+ *	Structure for FS_IOC_GETFSREFCOUNTS.
+ *
+ *	The memory layout for this call are the scalar values defined in
+ *	struct fsrefs_head, followed by two struct fsrefs that describe the
+ *	lower and upper bound of mappings to return, followed by an array of
+ *	struct fsrefs mappings.
+ *
+ *	fch_iflags control the output of the call, whereas fch_oflags report
+ *	on the overall record output.  fch_count should be set to the length
+ *	of the fch_recs array, and fch_entries will be set to the number of
+ *	entries filled out during each call.  If fch_count is zero, the number
+ *	of refcount mappings will be returned in fch_entries, though no
+ *	mappings will be returned.  fch_reserved must be set to zero.
+ *
+ *	The two elements in the fch_keys array are used to constrain the
+ *	output.  The first element in the array should represent the lowest
+ *	disk mapping ("low key") that the user wants to learn about.  If this
+ *	value is all zeroes, the filesystem will return the first entry it
+ *	knows about.  For a subsequent call, the contents of
+ *	fsrefs_head.fch_recs[fsrefs_head.fch_count - 1] should be copied into
+ *	fch_keys[0] to have the kernel start where it left off.
+ *
+ *	The second element in the fch_keys array should represent the highest
+ *	disk mapping ("high key") that the user wants to learn about.  If this
+ *	value is all ones, the filesystem will not stop until it runs out of
+ *	mapping to return or runs out of space in fch_recs.
+ *
+ *	fcr_device can be either a 32-bit cookie representing a device, or a
+ *	32-bit dev_t if the FCH_OF_DEV_T flag is set.  fcr_physical and
+ *	fcr_length are expressed in units of bytes.  fcr_owners is the number
+ *	of owners.
+ */
+struct fsrefs {
+	__u32		fcr_device;	/* device id */
+	__u32		fcr_flags;	/* mapping flags */
+	__u64		fcr_physical;	/* device offset of segment */
+	__u64		fcr_owners;	/* number of owners */
+	__u64		fcr_length;	/* length of segment */
+	__u64		fcr_reserved[4];	/* must be zero */
+};
+
+struct fsrefs_head {
+	__u32		fch_iflags;	/* control flags */
+	__u32		fch_oflags;	/* output flags */
+	__u32		fch_count;	/* # of entries in array incl. input */
+	__u32		fch_entries;	/* # of entries filled in (output). */
+	__u64		fch_reserved[6];	/* must be zero */
+
+	struct fsrefs	fch_keys[2];	/* low and high keys for the mapping search */
+	struct fsrefs	fch_recs[];	/* returned records */
+};
+
+/* Size of an fsrefs_head with room for nr records. */
+static inline unsigned long long
+fsrefs_sizeof(
+	unsigned int	nr)
+{
+	return sizeof(struct fsrefs_head) + nr * sizeof(struct fsrefs);
+}
+
+/* Start the next fsrefs query at the end of the current query results. */
+static inline void
+fsrefs_advance(
+	struct fsrefs_head	*head)
+{
+	head->fch_keys[0] = head->fch_recs[head->fch_entries - 1];
+}
+
+/*	fch_iflags values - set by FS_IOC_GETFSREFCOUNTS caller in the header. */
+/* no flags defined yet */
+#define FCH_IF_VALID		0
+
+/*	fch_oflags values - returned in the header segment only. */
+#define FCH_OF_DEV_T		0x1	/* fcr_device values will be dev_t */
+
+/*	fcr_flags values - returned for each non-header segment */
+#define FCR_OF_LAST		(1U << 0)	/* segment is the last in the dataset */
+
+/* XXX stealing XFS_IOC_GETBIOSIZE */
+#define FS_IOC_GETFSREFCOUNTS		_IOWR('X', 47, struct fsrefs_head)
+
+#endif /* _LINUX_FSREFCOUNTS_H */