afs: Add metadata xattrs

Add xattrs to allow the user to get/set metadata in lieu of having pioctl()
available.  The following xattrs are now available:

 - "afs.cell"

   The name of the cell in which the vnode's volume resides.

 - "afs.fid"

   The volume ID, vnode ID and vnode uniquifier of the file as three hex
   numbers separated by colons.

 - "afs.volume"

   The name of the volume in which the vnode resides.

For example:

	# getfattr -d -m ".*" /mnt/scratch
	getfattr: Removing leading '/' from absolute path names
	# file: mnt/scratch
	afs.cell="mycell.myorg.org"
	afs.fid="10000b:1:1"
	afs.volume="scratch"

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/afs/Makefile b/fs/afs/Makefile
index 4f64b95..095c541 100644 (file)
--- a/fs/afs/Makefile
+++ b/fs/afs/Makefile
@@ -27,6 +27,7 @@ kafs-objs := \
        vlocation.o \
        vnode.o \
        volume.o \
-       write.o
+       write.o \
+       xattr.o
 
 obj-$(CONFIG_AFS_FS)  := kafs.o

diff --git a/fs/afs/dir.c b/fs/afs/dir.c
index 949f960..613a770 100644 (file)
--- a/fs/afs/dir.c
+++ b/fs/afs/dir.c
@@ -61,6 +61,7 @@ const struct inode_operations afs_dir_inode_operations = {
        .permission     = afs_permission,
        .getattr        = afs_getattr,
        .setattr        = afs_setattr,
+       .listxattr      = afs_listxattr,
 };
 
 const struct dentry_operations afs_fs_dentry_operations = {

diff --git a/fs/afs/file.c b/fs/afs/file.c
index 0d5b850..510cba1 100644 (file)
--- a/fs/afs/file.c
+++ b/fs/afs/file.c
@@ -46,6 +46,7 @@ const struct inode_operations afs_file_inode_operations = {
        .getattr        = afs_getattr,
        .setattr        = afs_setattr,
        .permission     = afs_permission,
+       .listxattr      = afs_listxattr,
 };
 
 const struct address_space_operations afs_fs_aops = {

diff --git a/fs/afs/inode.c b/fs/afs/inode.c
index aae55dd..342316a 100644 (file)
--- a/fs/afs/inode.c
+++ b/fs/afs/inode.c
@@ -28,6 +28,11 @@ struct afs_iget_data {
        struct afs_volume       *volume;        /* volume on which resides */
 };
 
+static const struct inode_operations afs_symlink_inode_operations = {
+       .get_link       = page_get_link,
+       .listxattr      = afs_listxattr,
+};
+
 /*
  * map the AFS file status to the inode member variables
  */
@@ -67,7 +72,7 @@ static int afs_inode_map_status(struct afs_vnode *vnode, struct key *key)
                        inode->i_fop    = &afs_mntpt_file_operations;
                } else {
                        inode->i_mode   = S_IFLNK | vnode->status.mode;
-                       inode->i_op     = &page_symlink_inode_operations;
+                       inode->i_op     = &afs_symlink_inode_operations;
                }
                inode_nohighmem(inode);
                break;

diff --git a/fs/afs/internal.h b/fs/afs/internal.h
index 4e25566..82e1655 100644 (file)
--- a/fs/afs/internal.h
+++ b/fs/afs/internal.h
@@ -731,6 +731,11 @@ extern int afs_writeback_all(struct afs_vnode *);
 extern int afs_flush(struct file *, fl_owner_t);
 extern int afs_fsync(struct file *, loff_t, loff_t, int);
 
+/*
+ * xattr.c
+ */
+extern const struct xattr_handler *afs_xattr_handlers[];
+extern ssize_t afs_listxattr(struct dentry *, char *, size_t);
 
 /*****************************************************************************/
 /*

diff --git a/fs/afs/mntpt.c b/fs/afs/mntpt.c
index bd3b65c..690fea9 100644 (file)
--- a/fs/afs/mntpt.c
+++ b/fs/afs/mntpt.c
@@ -35,6 +35,7 @@ const struct inode_operations afs_mntpt_inode_operations = {
        .lookup         = afs_mntpt_lookup,
        .readlink       = page_readlink,
        .getattr        = afs_getattr,
+       .listxattr      = afs_listxattr,
 };
 
 const struct inode_operations afs_autocell_inode_operations = {

diff --git a/fs/afs/super.c b/fs/afs/super.c
index c79633e..67680c2 100644 (file)
--- a/fs/afs/super.c
+++ b/fs/afs/super.c
@@ -319,6 +319,7 @@ static int afs_fill_super(struct super_block *sb,
        sb->s_blocksize_bits    = PAGE_SHIFT;
        sb->s_magic             = AFS_FS_MAGIC;
        sb->s_op                = &afs_super_ops;
+       sb->s_xattr             = afs_xattr_handlers;
        ret = super_setup_bdi(sb);
        if (ret)
                return ret;

diff --git a/fs/afs/xattr.c b/fs/afs/xattr.c
new file mode 100644 (file)
index 0000000..2830e4f
--- /dev/null
+++ b/fs/afs/xattr.c
@@ -0,0 +1,121 @@
+/* Extended attribute handling for AFS.  We use xattrs to get and set metadata
+ * instead of providing pioctl().
+ *
+ * Copyright (C) 2017 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public Licence
+ * as published by the Free Software Foundation; either version
+ * 2 of the Licence, or (at your option) any later version.
+ */
+
+#include <linux/slab.h>
+#include <linux/fs.h>
+#include <linux/xattr.h>
+#include "internal.h"
+
+static const char afs_xattr_list[] =
+       "afs.cell\0"
+       "afs.fid\0"
+       "afs.volume";
+
+/*
+ * Retrieve a list of the supported xattrs.
+ */
+ssize_t afs_listxattr(struct dentry *dentry, char *buffer, size_t size)
+{
+       if (size == 0)
+               return sizeof(afs_xattr_list);
+       if (size < sizeof(afs_xattr_list))
+               return -ERANGE;
+       memcpy(buffer, afs_xattr_list, sizeof(afs_xattr_list));
+       return sizeof(afs_xattr_list);
+}
+
+/*
+ * Get the name of the cell on which a file resides.
+ */
+static int afs_xattr_get_cell(const struct xattr_handler *handler,
+                             struct dentry *dentry,
+                             struct inode *inode, const char *name,
+                             void *buffer, size_t size)
+{
+       struct afs_vnode *vnode = AFS_FS_I(inode);
+       struct afs_cell *cell = vnode->volume->cell;
+       size_t namelen;
+
+       namelen = strlen(cell->name);
+       if (size == 0)
+               return namelen;
+       if (namelen > size)
+               return -ERANGE;
+       memcpy(buffer, cell->name, size);
+       return namelen;
+}
+
+static const struct xattr_handler afs_xattr_afs_cell_handler = {
+       .name   = "afs.cell",
+       .get    = afs_xattr_get_cell,
+};
+
+/*
+ * Get the volume ID, vnode ID and vnode uniquifier of a file as a sequence of
+ * hex numbers separated by colons.
+ */
+static int afs_xattr_get_fid(const struct xattr_handler *handler,
+                            struct dentry *dentry,
+                            struct inode *inode, const char *name,
+                            void *buffer, size_t size)
+{
+       struct afs_vnode *vnode = AFS_FS_I(inode);
+       char text[8 + 1 + 8 + 1 + 8 + 1];
+       size_t len;
+
+       len = sprintf(text, "%x:%x:%x",
+                     vnode->fid.vid, vnode->fid.vnode, vnode->fid.unique);
+       if (size == 0)
+               return len;
+       if (len > size)
+               return -ERANGE;
+       memcpy(buffer, text, len);
+       return len;
+}
+
+static const struct xattr_handler afs_xattr_afs_fid_handler = {
+       .name   = "afs.fid",
+       .get    = afs_xattr_get_fid,
+};
+
+/*
+ * Get the name of the volume on which a file resides.
+ */
+static int afs_xattr_get_volume(const struct xattr_handler *handler,
+                             struct dentry *dentry,
+                             struct inode *inode, const char *name,
+                             void *buffer, size_t size)
+{
+       struct afs_vnode *vnode = AFS_FS_I(inode);
+       const char *volname = vnode->volume->vlocation->vldb.name;
+       size_t namelen;
+
+       namelen = strlen(volname);
+       if (size == 0)
+               return namelen;
+       if (namelen > size)
+               return -ERANGE;
+       memcpy(buffer, volname, size);
+       return namelen;
+}
+
+static const struct xattr_handler afs_xattr_afs_volume_handler = {
+       .name   = "afs.volume",
+       .get    = afs_xattr_get_volume,
+};
+
+const struct xattr_handler *afs_xattr_handlers[] = {
+       &afs_xattr_afs_cell_handler,
+       &afs_xattr_afs_fid_handler,
+       &afs_xattr_afs_volume_handler,
+       NULL
+};