fs/afs/xattr.c

   1 /* Extended attribute handling for AFS.  We use xattrs to get and set metadata
   2  * instead of providing pioctl().
   3  *
   4  * Copyright (C) 2017 Red Hat, Inc. All Rights Reserved.
   5  * Written by David Howells (dhowells@redhat.com)
   6  *
   7  * This program is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU General Public Licence
   9  * as published by the Free Software Foundation; either version
  10  * 2 of the Licence, or (at your option) any later version.
  11  */
  12
  13 #include <linux/slab.h>
  14 #include <linux/fs.h>
  15 #include <linux/xattr.h>
  16 #include "internal.h"
  17
  18 static const char afs_xattr_list[] =
  19         "afs.cell\0"
  20         "afs.fid\0"
  21         "afs.volume";
  22
  23 /*
  24  * Retrieve a list of the supported xattrs.
  25  */
  26 ssize_t afs_listxattr(struct dentry *dentry, char *buffer, size_t size)
  27 {
  28         if (size == 0)
  29                 return sizeof(afs_xattr_list);
  30         if (size < sizeof(afs_xattr_list))
  31                 return -ERANGE;
  32         memcpy(buffer, afs_xattr_list, sizeof(afs_xattr_list));
  33         return sizeof(afs_xattr_list);
  34 }
  35
  36 /*
  37  * Get the name of the cell on which a file resides.
  38  */
  39 static int afs_xattr_get_cell(const struct xattr_handler *handler,
  40                               struct dentry *dentry,
  41                               struct inode *inode, const char *name,
  42                               void *buffer, size_t size)
  43 {
  44         struct afs_vnode *vnode = AFS_FS_I(inode);
  45         struct afs_cell *cell = vnode->volume->cell;
  46         size_t namelen;
  47
  48         namelen = cell->name_len;
  49         if (size == 0)
  50                 return namelen;
  51         if (namelen > size)
  52                 return -ERANGE;
  53         memcpy(buffer, cell->name, size);
  54         return namelen;
  55 }
  56
  57 static const struct xattr_handler afs_xattr_afs_cell_handler = {
  58         .name   = "afs.cell",
  59         .get    = afs_xattr_get_cell,
  60 };
  61
  62 /*
  63  * Get the volume ID, vnode ID and vnode uniquifier of a file as a sequence of
  64  * hex numbers separated by colons.
  65  */
  66 static int afs_xattr_get_fid(const struct xattr_handler *handler,
  67                              struct dentry *dentry,
  68                              struct inode *inode, const char *name,
  69                              void *buffer, size_t size)
  70 {
  71         struct afs_vnode *vnode = AFS_FS_I(inode);
  72         char text[8 + 1 + 8 + 1 + 8 + 1];
  73         size_t len;
  74
  75         len = sprintf(text, "%llx:%llx:%x",
  76                       vnode->fid.vid, vnode->fid.vnode, vnode->fid.unique);
  77         if (size == 0)
  78                 return len;
  79         if (len > size)
  80                 return -ERANGE;
  81         memcpy(buffer, text, len);
  82         return len;
  83 }
  84
  85 static const struct xattr_handler afs_xattr_afs_fid_handler = {
  86         .name   = "afs.fid",
  87         .get    = afs_xattr_get_fid,
  88 };
  89
  90 /*
  91  * Get the name of the volume on which a file resides.
  92  */
  93 static int afs_xattr_get_volume(const struct xattr_handler *handler,
  94                               struct dentry *dentry,
  95                               struct inode *inode, const char *name,
  96                               void *buffer, size_t size)
  97 {
  98         struct afs_vnode *vnode = AFS_FS_I(inode);
  99         const char *volname = vnode->volume->name;
 100         size_t namelen;
 101
 102         namelen = strlen(volname);
 103         if (size == 0)
 104                 return namelen;
 105         if (namelen > size)
 106                 return -ERANGE;
 107         memcpy(buffer, volname, size);
 108         return namelen;
 109 }
 110
 111 static const struct xattr_handler afs_xattr_afs_volume_handler = {
 112         .name   = "afs.volume",
 113         .get    = afs_xattr_get_volume,
 114 };
 115
 116 const struct xattr_handler *afs_xattr_handlers[] = {
 117         &afs_xattr_afs_cell_handler,
 118         &afs_xattr_afs_fid_handler,
 119         &afs_xattr_afs_volume_handler,
 120         NULL
 121 };