[PATCH v5 18/25] xfsprogs: Add parent pointer ioctl

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From: Allison Henderson <allison.henderson@xxxxxxxxxx>

Source kernel commit: 5e5cdd593342c5ff8aeef9daaa93293f63079b4b

This patch adds a new file ioctl to retrieve the parent pointer of a
given inode

Signed-off-by: Allison Henderson <allison.henderson@xxxxxxxxxx>
---
 libxfs/xfs_fs.h     | 74 +++++++++++++++++++++++++++++++++++++++++++++
 libxfs/xfs_parent.c | 10 ++++++
 libxfs/xfs_parent.h |  2 ++
 man/man3/xfsctl.3   | 55 +++++++++++++++++++++++++++++++++
 4 files changed, 141 insertions(+)

diff --git a/libxfs/xfs_fs.h b/libxfs/xfs_fs.h
index b0b4d7a3aa15..9e59a1fdfb0c 100644
--- a/libxfs/xfs_fs.h
+++ b/libxfs/xfs_fs.h
@@ -752,6 +752,79 @@ struct xfs_scrub_metadata {
 				 XFS_SCRUB_OFLAG_NO_REPAIR_NEEDED)
 #define XFS_SCRUB_FLAGS_ALL	(XFS_SCRUB_FLAGS_IN | XFS_SCRUB_FLAGS_OUT)
 
+#define XFS_PPTR_MAXNAMELEN				256
+
+/* return parents of the handle, not the open fd */
+#define XFS_PPTR_IFLAG_HANDLE  (1U << 0)
+
+/* target was the root directory */
+#define XFS_PPTR_OFLAG_ROOT    (1U << 1)
+
+/* Cursor is done iterating pptrs */
+#define XFS_PPTR_OFLAG_DONE    (1U << 2)
+
+ #define XFS_PPTR_FLAG_ALL     (XFS_PPTR_IFLAG_HANDLE | XFS_PPTR_OFLAG_ROOT | \
+				XFS_PPTR_OFLAG_DONE)
+
+/* Get an inode parent pointer through ioctl */
+struct xfs_parent_ptr {
+	__u64		xpp_ino;			/* Inode */
+	__u32		xpp_gen;			/* Inode generation */
+	__u32		xpp_diroffset;			/* Directory offset */
+	__u64		xpp_rsvd;			/* Reserved */
+	__u8		xpp_name[XFS_PPTR_MAXNAMELEN];	/* File name */
+};
+
+/* Iterate through an inodes parent pointers */
+struct xfs_pptr_info {
+	/* File handle, if XFS_PPTR_IFLAG_HANDLE is set */
+	struct xfs_handle		pi_handle;
+
+	/*
+	 * Structure to track progress in iterating the parent pointers.
+	 * Must be initialized to zeroes before the first ioctl call, and
+	 * not touched by callers after that.
+	 */
+	struct xfs_attrlist_cursor	pi_cursor;
+
+	/* Operational flags: XFS_PPTR_*FLAG* */
+	__u32				pi_flags;
+
+	/* Must be set to zero */
+	__u32				pi_reserved;
+
+	/* # of entries in array */
+	__u32				pi_ptrs_size;
+
+	/* # of entries filled in (output) */
+	__u32				pi_ptrs_used;
+
+	/* Must be set to zero */
+	__u64				pi_reserved2[6];
+
+	/*
+	 * An array of struct xfs_parent_ptr follows the header
+	 * information. Use xfs_ppinfo_to_pp() to access the
+	 * parent pointer array entries.
+	 */
+	struct xfs_parent_ptr		pi_parents[];
+};
+
+static inline size_t
+xfs_pptr_info_sizeof(int nr_ptrs)
+{
+	return sizeof(struct xfs_pptr_info) +
+	       (nr_ptrs * sizeof(struct xfs_parent_ptr));
+}
+
+static inline struct xfs_parent_ptr*
+xfs_ppinfo_to_pp(
+	struct xfs_pptr_info	*info,
+	int			idx)
+{
+	return &info->pi_parents[idx];
+}
+
 /*
  * ioctl limits
  */
@@ -797,6 +870,7 @@ struct xfs_scrub_metadata {
 /*	XFS_IOC_GETFSMAP ------ hoisted 59         */
 #define XFS_IOC_SCRUB_METADATA	_IOWR('X', 60, struct xfs_scrub_metadata)
 #define XFS_IOC_AG_GEOMETRY	_IOWR('X', 61, struct xfs_ag_geometry)
+#define XFS_IOC_GETPARENTS	_IOWR('X', 62, struct xfs_parent_ptr)
 
 /*
  * ioctl commands that replace IRIX syssgi()'s
diff --git a/libxfs/xfs_parent.c b/libxfs/xfs_parent.c
index f9513cde3b01..2605704f854b 100644
--- a/libxfs/xfs_parent.c
+++ b/libxfs/xfs_parent.c
@@ -28,6 +28,16 @@
 #include "xfs_format.h"
 #include "xfs_trans_space.h"
 
+/* Initializes a xfs_parent_ptr from an xfs_parent_name_rec */
+void
+xfs_init_parent_ptr(struct xfs_parent_ptr		*xpp,
+		    const struct xfs_parent_name_rec	*rec)
+{
+	xpp->xpp_ino = be64_to_cpu(rec->p_ino);
+	xpp->xpp_gen = be32_to_cpu(rec->p_gen);
+	xpp->xpp_diroffset = be32_to_cpu(rec->p_diroffset);
+}
+
 /*
  * Parent pointer attribute handling.
  *
diff --git a/libxfs/xfs_parent.h b/libxfs/xfs_parent.h
index 9021241ad65b..898842b4532d 100644
--- a/libxfs/xfs_parent.h
+++ b/libxfs/xfs_parent.h
@@ -24,6 +24,8 @@ void xfs_init_parent_name_rec(struct xfs_parent_name_rec *rec,
 			      uint32_t p_diroffset);
 void xfs_init_parent_name_irec(struct xfs_parent_name_irec *irec,
 			       struct xfs_parent_name_rec *rec);
+void xfs_init_parent_ptr(struct xfs_parent_ptr *xpp,
+			 const struct xfs_parent_name_rec *rec);
 int xfs_parent_init(xfs_mount_t *mp, struct xfs_parent_defer **parentp);
 int xfs_parent_defer_add(struct xfs_trans *tp, struct xfs_parent_defer *parent,
 			 struct xfs_inode *dp, struct xfs_name *parent_name,
diff --git a/man/man3/xfsctl.3 b/man/man3/xfsctl.3
index 4a0d4d08d083..7cc97499e0ba 100644
--- a/man/man3/xfsctl.3
+++ b/man/man3/xfsctl.3
@@ -321,6 +321,61 @@ They are all subject to change and should not be called directly
 by applications.
 XFS_IOC_FSSETDM_BY_HANDLE is not supported as of Linux 5.5.
 
+.PP
+.TP
+.B XFS_IOC_GETPARENTS
+This command is used to get a files parent pointers.  Parent pointers are
+file attributes used to store meta data information about an inodes parent.
+This command takes a xfs_pptr_info structure with trailing array of
+struct xfs_parent_ptr as an input to store an inodes parents. The
+xfs_pptr_info_sizeof() and xfs_ppinfo_to_pp() routines are provided to
+create and iterate through these structures.  The number of pointers stored
+in the array is indicated by the xfs_pptr_info.used field, and the
+XFS_PPTR_OFLAG_DONE flag will be set in xfs_pptr_info.flags when there are
+no more parent pointers to be read.  The below code is an example
+of XFS_IOC_GETPARENTS usage:
+
+.nf
+#include<stdio.h>
+#include<string.h>
+#include<errno.h>
+#include<xfs/linux.h>
+#include<xfs/xfs.h>
+#include<xfs/xfs_types.h>
+#include<xfs/xfs_fs.h>
+
+int main() {
+	struct xfs_pptr_info	*pi;
+	struct xfs_parent_ptr	*p;
+	int			i, error, fd, nr_ptrs = 4;
+
+	unsigned char buffer[xfs_pptr_info_sizeof(nr_ptrs)];
+	memset(buffer, 0, sizeof(buffer));
+	pi = (struct xfs_pptr_info *)&buffer;
+	pi->pi_ptrs_size = nr_ptrs;
+
+	fd = open("/mnt/test/foo.txt", O_RDONLY | O_CREAT);
+	if (fd  == -1)
+		return errno;
+
+	do {
+		error = ioctl(fd, XFS_IOC_GETPARENTS, pi);
+		if (error)
+			return error;
+
+		for (i = 0; i < pi->pi_ptrs_used; i++) {
+			p = xfs_ppinfo_to_pp(pi, i);
+			printf("inode		= %llu\\n", (unsigned long long)p->xpp_ino);
+			printf("generation	= %u\\n", (unsigned int)p->xpp_gen);
+			printf("diroffset	= %u\\n", (unsigned int)p->xpp_diroffset);
+			printf("name		= \\"%s\\"\\n\\n", (char *)p->xpp_name);
+		}
+	} while (!pi->pi_flags & XFS_PPTR_OFLAG_DONE);
+
+	return 0;
+}
+.fi
+
 .SS Filesystem Operations
 In order to effect one of the following operations, the pathname
 and descriptor arguments passed to
-- 
2.25.1




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