[PATCH v3 17/17] Add parent pointer ioctl

[Allison Henderson <allison.henderson@oracle.com>]

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

Signed-off-by: Allison Henderson <allison.henderson@oracle.com>
---
 fs/xfs/libxfs/xfs_attr.c | 67 ++++++++++++++++++++++++++++++++++++++++++++++++
 fs/xfs/libxfs/xfs_fs.h   |  1 +
 fs/xfs/xfs_attr.h        |  2 ++
 fs/xfs/xfs_attr_list.c   |  3 +++
 fs/xfs/xfs_ioctl.c       | 48 +++++++++++++++++++++++++++++++++-
 5 files changed, 120 insertions(+), 1 deletion(-)

diff --git a/fs/xfs/libxfs/xfs_attr.c b/fs/xfs/libxfs/xfs_attr.c
index 9d4d883..d2be842 100644
--- a/fs/xfs/libxfs/xfs_attr.c
+++ b/fs/xfs/libxfs/xfs_attr.c
@@ -134,6 +134,73 @@ xfs_attr_get_ilocked(
 		return xfs_attr_node_get(args);
 }
 
+/*
+ * Get the parent pointer for a given inode
+ * Caller will need to allocate a buffer pointed to by xpnir->p_name
+ * and store the buffer size in xpnir->p_namelen.  The parent
+ * pointer will be stored in the given xfs_parent_name_irec
+ *
+ * Returns 0 on success and non zero on error
+ */
+int
+xfs_attr_get_parent_pointer(struct xfs_inode		*ip,
+			    struct xfs_parent_name_irec *xpnir)
+{
+	struct attrlist			*alist;
+	struct attrlist_ent		*aent;
+	struct attrlist_cursor_kern     cursor;
+	struct xfs_parent_name_rec	*xpnr;
+	char				*namebuf;
+	int                             error = 0;
+	unsigned int                    flags = ATTR_PARENT;
+
+	/* Allocate a buffer to store the attribute names */
+	namebuf = kmem_zalloc_large(XFS_XATTR_LIST_MAX, KM_SLEEP);
+	if (!namebuf)
+		return -ENOMEM;
+
+	/* Get all attribute names that have the ATTR_PARENT flag */
+	memset(&cursor, 0, sizeof(struct attrlist_cursor_kern));
+	error = xfs_attr_list(ip, namebuf, XFS_XATTR_LIST_MAX, flags, &cursor);
+	if (error)
+		goto out_kfree;
+
+	alist = (struct attrlist *)namebuf;
+
+	/* There should never be more than one parent pointer */
+	ASSERT(alist->al_count == 1);
+
+	aent = (struct attrlist_ent *) &namebuf[alist->al_offset[0]];
+	xpnr = (struct xfs_parent_name_rec *)(aent->a_name);
+
+	/*
+	 * The value of the parent pointer attribute should be the file name
+	 * So we check the value length of the attribute entry against the name
+	 * length of the parent name record to make sure the caller gave enough
+	 * buffer space to store the file name (plus a null terminator)
+	 */
+	if (aent->a_valuelen >= xpnir->p_namelen) {
+		error = -ERANGE;
+		goto out_kfree;
+	}
+
+	xpnir->p_namelen = aent->a_valuelen + 1;
+	memset((void *)(xpnir->p_name), 0, xpnir->p_namelen);
+	error = xfs_attr_get(ip, (char *)xpnr,
+			     sizeof(struct xfs_parent_name_rec),
+			     (unsigned char *)(xpnir->p_name),
+			     (int *)&(xpnir->p_namelen), flags);
+	if (error)
+		goto out_kfree;
+
+	xfs_init_parent_name_irec(xpnir, xpnr);
+
+out_kfree:
+	kmem_free(namebuf);
+
+	return error;
+}
+
 /* Retrieve an extended attribute by name, and its value. */
 int
 xfs_attr_get(
diff --git a/fs/xfs/libxfs/xfs_fs.h b/fs/xfs/libxfs/xfs_fs.h
index b8108f8..2f9ca2c 100644
--- a/fs/xfs/libxfs/xfs_fs.h
+++ b/fs/xfs/libxfs/xfs_fs.h
@@ -512,6 +512,7 @@ typedef struct xfs_swapext
 #define XFS_IOC_ZERO_RANGE	_IOW ('X', 57, struct xfs_flock64)
 #define XFS_IOC_FREE_EOFBLOCKS	_IOR ('X', 58, struct xfs_fs_eofblocks)
 /*	XFS_IOC_GETFSMAP ------ hoisted 59         */
+#define XFS_IOC_GETPPOINTER	_IOR ('X', 61, struct xfs_parent_name_irec)
 
 /*
  * ioctl commands that replace IRIX syssgi()'s
diff --git a/fs/xfs/xfs_attr.h b/fs/xfs/xfs_attr.h
index 0829687..0ec3458 100644
--- a/fs/xfs/xfs_attr.h
+++ b/fs/xfs/xfs_attr.h
@@ -172,6 +172,8 @@ int xfs_attr_get(struct xfs_inode *ip, const unsigned char *name,
 		int flags);
 int xfs_attr_set(struct xfs_inode *dp, const unsigned char *name,
 		size_t namelen, unsigned char *value, int valuelen, int flags);
+int xfs_attr_get_parent_pointer(struct xfs_inode *ip,
+				struct xfs_parent_name_irec *xpnir);
 int xfs_attr_set_args(struct xfs_da_args *args, int flags, bool roll_trans);
 int xfs_attr_remove(struct xfs_inode *dp, const unsigned char *name,
 		size_t namelen, int flags);
diff --git a/fs/xfs/xfs_attr_list.c b/fs/xfs/xfs_attr_list.c
index 7740c8a..78fc477 100644
--- a/fs/xfs/xfs_attr_list.c
+++ b/fs/xfs/xfs_attr_list.c
@@ -534,6 +534,9 @@ xfs_attr_put_listent(
 	if (((context->flags & ATTR_ROOT) == 0) !=
 	    ((flags & XFS_ATTR_ROOT) == 0))
 		return;
+	if (((context->flags & ATTR_PARENT) == 0) !=
+	    ((flags & XFS_ATTR_PARENT) == 0))
+		return;
 
 	arraytop = sizeof(*alist) +
 			context->count * sizeof(alist->al_offset[0]);
diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c
index 4664314..5492607 100644
--- a/fs/xfs/xfs_ioctl.c
+++ b/fs/xfs/xfs_ioctl.c
@@ -44,6 +44,7 @@
 #include "xfs_btree.h"
 #include <linux/fsmap.h>
 #include "xfs_fsmap.h"
+#include "xfs_attr.h"
 
 #include <linux/capability.h>
 #include <linux/cred.h>
@@ -1710,6 +1711,50 @@ xfs_ioc_getfsmap(
 	return 0;
 }
 
+/*
+ * IOCTL routine to get the parent pointer of an inode and return it to user
+ * space.  Caller must pass an struct xfs_parent_name_irec with a name buffer
+ * large enough to hold the file name.  Returns 0 on success or non-zero on
+ * failure
+ */
+STATIC int
+xfs_ioc_get_parent_pointer(
+	struct file			*filp,
+	void				__user *arg)
+{
+	struct inode			*inode = file_inode(filp);
+	struct xfs_inode		*ip = XFS_I(inode);
+	struct xfs_parent_name_irec	xpnir;
+	char				*uname;
+	char				*kname;
+	int				error = 0;
+
+	copy_from_user(&xpnir, arg, sizeof(struct xfs_parent_name_irec));
+	uname = (char *)xpnir.p_name;
+
+	/*
+	 * Use kernel space memory to get the parent pointer name.
+	 * We'll copy it to the user space name back when we're done
+	 */
+	kname = kmem_zalloc_large(xpnir.p_namelen, KM_SLEEP);
+	if (!kname)
+		return -ENOMEM;
+
+	xpnir.p_name = kname;
+	error = xfs_attr_get_parent_pointer(ip, &xpnir);
+
+	if (error)
+		goto out;
+
+	copy_to_user(uname, xpnir.p_name, xpnir.p_namelen);
+	xpnir.p_name = uname;
+	copy_to_user(arg, &xpnir, sizeof(struct xfs_parent_name_irec));
+
+out:
+	kmem_free(kname);
+	return error;
+}
+
 int
 xfs_ioc_swapext(
 	xfs_swapext_t	*sxp)
@@ -1866,7 +1911,8 @@ xfs_file_ioctl(
 		return xfs_ioc_getxflags(ip, arg);
 	case XFS_IOC_SETXFLAGS:
 		return xfs_ioc_setxflags(ip, filp, arg);
-
+	case XFS_IOC_GETPPOINTER:
+		return xfs_ioc_get_parent_pointer(filp, arg);
 	case XFS_IOC_FSSETDM: {
 		struct fsdmidata	dmi;
 
-- 
2.7.4