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,
  23  * CA 95054 USA or visit www.sun.com if you need additional information or
  24  * have any questions.
  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/jbd.h>
  44 #include <linux/module.h>
  45 #include <linux/kmod.h>
  46 #include <linux/slab.h>
  47 #include <libcfs/libcfs.h>
  48 #include <lustre_fsfilt.h>
  49
  50 CFS_LIST_HEAD(fsfilt_types);
  51
  52 static struct fsfilt_operations *fsfilt_search_type(const char *type)
  53 {
  54         struct fsfilt_operations *found;
  55         struct list_head *p;
  56
  57         list_for_each(p, &fsfilt_types) {
  58                 found = list_entry(p, struct fsfilt_operations, fs_list);
  59                 if (!strcmp(found->fs_type, type)) {
  60                         return found;
  61                 }
  62         }
  63         return NULL;
  64 }
  65
  66 int fsfilt_register_ops(struct fsfilt_operations *fs_ops)
  67 {
  68         struct fsfilt_operations *found;
  69
  70         /* lock fsfilt_types list */
  71         if ((found = fsfilt_search_type(fs_ops->fs_type))) {
  72                 if (found != fs_ops) {
  73                         CERROR("different operations for type %s\n",
  74                                fs_ops->fs_type);
  75                         /* unlock fsfilt_types list */
  76                         RETURN(-EEXIST);
  77                 }
  78         } else {
  79                 PORTAL_MODULE_USE;
  80                 list_add(&fs_ops->fs_list, &fsfilt_types);
  81         }
  82
  83         /* unlock fsfilt_types list */
  84         return 0;
  85 }
  86
  87 void fsfilt_unregister_ops(struct fsfilt_operations *fs_ops)
  88 {
  89         struct list_head *p;
  90
  91         /* lock fsfilt_types list */
  92         list_for_each(p, &fsfilt_types) {
  93                 struct fsfilt_operations *found;
  94
  95                 found = list_entry(p, typeof(*found), fs_list);
  96                 if (found == fs_ops) {
  97                         list_del(p);
  98                         PORTAL_MODULE_UNUSE;
  99                         break;
 100                 }
 101         }
 102         /* unlock fsfilt_types list */
 103 }
 104
 105 struct fsfilt_operations *fsfilt_get_ops(const char *type)
 106 {
 107         struct fsfilt_operations *fs_ops;
 108
 109         /* lock fsfilt_types list */
 110         if (!(fs_ops = fsfilt_search_type(type))) {
 111                 char name[32];
 112                 int rc;
 113
 114                 snprintf(name, sizeof(name) - 1, "fsfilt_%s", type);
 115                 name[sizeof(name) - 1] = '\0';
 116
 117                 if (!(rc = request_module("%s", name))) {
 118                         fs_ops = fsfilt_search_type(type);
 119                         CDEBUG(D_INFO, "Loaded module '%s'\n", name);
 120                         if (!fs_ops)
 121                                 rc = -ENOENT;
 122                 }
 123
 124                 if (rc) {
 125                         CERROR("Can't find %s interface\n", name);
 126                         RETURN(ERR_PTR(rc < 0 ? rc : -rc));
 127                         /* unlock fsfilt_types list */
 128                 }
 129         }
 130         try_module_get(fs_ops->fs_owner);
 131         /* unlock fsfilt_types list */
 132
 133         return fs_ops;
 134 }
 135
 136 void fsfilt_put_ops(struct fsfilt_operations *fs_ops)
 137 {
 138         module_put(fs_ops->fs_owner);
 139 }
 140
 141
 142 EXPORT_SYMBOL(fsfilt_register_ops);
 143 EXPORT_SYMBOL(fsfilt_unregister_ops);
 144 EXPORT_SYMBOL(fsfilt_get_ops);
 145 EXPORT_SYMBOL(fsfilt_put_ops);