lustre/lvfs/fsfilt.c

   1 /* -*- mode: c; c-basic-offset: 8; indent-tabs-mode: nil; -*-
   2  * vim:expandtab:shiftwidth=8:tabstop=8:
   3  *
   4  * GPL HEADER START
   5  *
   6  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License version 2 only,
  10  * as published by the Free Software Foundation.
  11  *
  12  * This program is distributed in the hope that it will be useful, but
  13  * WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15  * General Public License version 2 for more details (a copy is included
  16  * in the LICENSE file that accompanied this code).
  17  *
  18  * You should have received a copy of the GNU General Public License
  19  * version 2 along with this program; If not, see
  20  * http://www.sun.com/software/products/lustre/docs/GPLv2.pdf
  21  *
  22  * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
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  25  *
  26  * GPL HEADER END
  27  */
  28 /*
  29  * Copyright  2008 Sun Microsystems, Inc. All rights reserved
  30  * Use is subject to license terms.
  31  */
  32 /*
  33  * This file is part of Lustre, http://www.lustre.org/
  34  * Lustre is a trademark of Sun Microsystems, Inc.
  35  */
  36
  37 #ifndef EXPORT_SYMTAB
  38 # define EXPORT_SYMTAB
  39 #endif
  40 #define DEBUG_SUBSYSTEM S_FILTER
  41
  42 #include <linux/fs.h>
  43 #include <linux/module.h>
  44 #include <linux/kmod.h>
  45 #include <linux/slab.h>
  46 #include <libcfs/kp30.h>
  47 #include <lustre_fsfilt.h>
  48
  49 LIST_HEAD(fsfilt_types);
  50
  51 static struct fsfilt_operations *fsfilt_search_type(const char *type)
  52 {
  53         struct fsfilt_operations *found;
  54         struct list_head *p;
  55
  56         list_for_each(p, &fsfilt_types) {
  57                 found = list_entry(p, struct fsfilt_operations, fs_list);
  58                 if (!strcmp(found->fs_type, type)) {
  59                         return found;
  60                 }
  61         }
  62         return NULL;
  63 }
  64
  65 int fsfilt_register_ops(struct fsfilt_operations *fs_ops)
  66 {
  67         struct fsfilt_operations *found;
  68
  69         /* lock fsfilt_types list */
  70         if ((found = fsfilt_search_type(fs_ops->fs_type))) {
  71                 if (found != fs_ops) {
  72                         CERROR("different operations for type %s\n",
  73                                fs_ops->fs_type);
  74                         /* unlock fsfilt_types list */
  75                         RETURN(-EEXIST);
  76                 }
  77         } else {
  78                 PORTAL_MODULE_USE;
  79                 list_add(&fs_ops->fs_list, &fsfilt_types);
  80         }
  81
  82         /* unlock fsfilt_types list */
  83         return 0;
  84 }
  85
  86 void fsfilt_unregister_ops(struct fsfilt_operations *fs_ops)
  87 {
  88         struct list_head *p;
  89
  90         /* lock fsfilt_types list */
  91         list_for_each(p, &fsfilt_types) {
  92                 struct fsfilt_operations *found;
  93
  94                 found = list_entry(p, typeof(*found), fs_list);
  95                 if (found == fs_ops) {
  96                         list_del(p);
  97                         PORTAL_MODULE_UNUSE;
  98                         break;
  99                 }
 100         }
 101         /* unlock fsfilt_types list */
 102 }
 103
 104 struct fsfilt_operations *fsfilt_get_ops(const char *type)
 105 {
 106         struct fsfilt_operations *fs_ops;
 107
 108         /* lock fsfilt_types list */
 109         if (!(fs_ops = fsfilt_search_type(type))) {
 110                 char name[32];
 111                 int rc;
 112
 113                 snprintf(name, sizeof(name) - 1, "fsfilt_%s", type);
 114                 name[sizeof(name) - 1] = '\0';
 115
 116                 if (!(rc = request_module("%s", name))) {
 117                         fs_ops = fsfilt_search_type(type);
 118                         CDEBUG(D_INFO, "Loaded module '%s'\n", name);
 119                         if (!fs_ops)
 120                                 rc = -ENOENT;
 121                 }
 122
 123                 if (rc) {
 124                         CERROR("Can't find %s interface\n", name);
 125                         RETURN(ERR_PTR(rc < 0 ? rc : -rc));
 126                         /* unlock fsfilt_types list */
 127                 }
 128         }
 129         try_module_get(fs_ops->fs_owner);
 130         /* unlock fsfilt_types list */
 131
 132         return fs_ops;
 133 }
 134
 135 void fsfilt_put_ops(struct fsfilt_operations *fs_ops)
 136 {
 137         module_put(fs_ops->fs_owner);
 138 }
 139
 140
 141 EXPORT_SYMBOL(fsfilt_register_ops);
 142 EXPORT_SYMBOL(fsfilt_unregister_ops);
 143 EXPORT_SYMBOL(fsfilt_get_ops);
 144 EXPORT_SYMBOL(fsfilt_put_ops);