vfs: add common GETFSMAP ioctl definitions

Add the GETFSMAP headers to the VFS kernel headers
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

include/uapi/linux/fsmap.h

+/*
+ * FS_IOC_GETFSMAP ioctl infrastructure.
+ *
+ * Copyright (C) 2017 Oracle.  All Rights Reserved.
+ *
+ * Author: Darrick J. Wong <darrick.wong@oracle.com>
+ */
+#ifndef _LINUX_FSMAP_H
+#define _LINUX_FSMAP_H
+
+#include <linux/types.h>
+
+/*
+ *	Structure for FS_IOC_GETFSMAP.
+ *
+ *	The memory layout for this call are the scalar values defined in
+ *	struct fsmap_head, followed by two struct fsmap that describe
+ *	the lower and upper bound of mappings to return, followed by an
+ *	array of struct fsmap mappings.
+ *
+ *	fmh_iflags control the output of the call, whereas fmh_oflags report
+ *	on the overall record output.  fmh_count should be set to the
+ *	length of the fmh_recs array, and fmh_entries will be set to the
+ *	number of entries filled out during each call.  If fmh_count is
+ *	zero, the number of reverse mappings will be returned in
+ *	fmh_entries, though no mappings will be returned.  fmh_reserved
+ *	must be set to zero.
+ *
+ *	The two elements in the fmh_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 fsmap_head.fmh_recs[fsmap_head.fmh_count - 1] should be
+ *	copied into fmh_keys[0] to have the kernel start where it left off.
+ *
+ *	The second element in the fmh_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
+ *	fmh_recs.
+ *
+ *	fmr_device can be either a 32-bit cookie representing a device, or
+ *	a 32-bit dev_t if the FMH_OF_DEV_T flag is set.  fmr_physical,
+ *	fmr_offset, and fmr_length are expressed in units of bytes.
+ *	fmr_owner is either an inode number, or a special value if
+ *	FMR_OF_SPECIAL_OWNER is set in fmr_flags.
+ */
+struct fsmap {
+	__u32		fmr_device;	/* device id */
+	__u32		fmr_flags;	/* mapping flags */
+	__u64		fmr_physical;	/* device offset of segment */
+	__u64		fmr_owner;	/* owner id */
+	__u64		fmr_offset;	/* file offset of segment */
+	__u64		fmr_length;	/* length of segment */
+	__u64		fmr_reserved[3];	/* must be zero */
+};
+
+struct fsmap_head {
+	__u32		fmh_iflags;	/* control flags */
+	__u32		fmh_oflags;	/* output flags */
+	__u32		fmh_count;	/* # of entries in array incl. input */
+	__u32		fmh_entries;	/* # of entries filled in (output). */
+	__u64		fmh_reserved[6];	/* must be zero */
+
+	struct fsmap	fmh_keys[2];	/* low and high keys for the mapping search */
+	struct fsmap	fmh_recs[];	/* returned records */
+};
+
+/* Size of an fsmap_head with room for nr records. */
+static inline size_t
+fsmap_sizeof(
+	unsigned int	nr)
+{
+	return sizeof(struct fsmap_head) + nr * sizeof(struct fsmap);
+}
+
+/* Start the next fsmap query at the end of the current query results. */
+static inline void
+fsmap_advance(
+	struct fsmap_head	*head)
+{
+	head->fmh_keys[0] = head->fmh_recs[head->fmh_entries - 1];
+}
+
+/*	fmh_iflags values - set by FS_IOC_GETFSMAP caller in the header. */
+/* no flags defined yet */
+#define FMH_IF_VALID		0
+
+/*	fmh_oflags values - returned in the header segment only. */
+#define FMH_OF_DEV_T		0x1	/* fmr_device values will be dev_t */
+
+/*	fmr_flags values - returned for each non-header segment */
+#define FMR_OF_PREALLOC		0x1	/* segment = unwritten pre-allocation */
+#define FMR_OF_ATTR_FORK	0x2	/* segment = attribute fork */
+#define FMR_OF_EXTENT_MAP	0x4	/* segment = extent map */
+#define FMR_OF_SHARED		0x8	/* segment = shared with another file */
+#define FMR_OF_SPECIAL_OWNER	0x10	/* owner is a special value */
+#define FMR_OF_LAST		0x20	/* segment is the last in the FS */
+
+/* Each FS gets to define its own special owner codes. */
+#define FMR_OWNER(type, code)	(((__u64)type << 32) | \
+				 ((__u64)code & 0xFFFFFFFFULL))
+#define FMR_OWNER_TYPE(owner)	((__u32)((__u64)owner >> 32))
+#define FMR_OWNER_CODE(owner)	((__u32)(((__u64)owner & 0xFFFFFFFFULL)))
+#define FMR_OWN_FREE		FMR_OWNER(0, 1) /* free space */
+#define FMR_OWN_UNKNOWN		FMR_OWNER(0, 2) /* unknown owner */
+#define FMR_OWN_METADATA	FMR_OWNER(0, 3) /* metadata */
+
+#define FS_IOC_GETFSMAP		_IOWR('X', 59, struct fsmap_head)
+
+#endif /* _LINUX_FSMAP_H */