include/wrapper/writeback.h

   1 /* SPDX-License-Identifier: (GPL-2.0-only or LGPL-2.1-only)
   2  *
   3  * wrapper/writeback.h
   4  *
   5  * wrapper around global_dirty_limit read. Using KALLSYMS with KALLSYMS_ALL
   6  * to get its address when available, else we need to have a kernel that
   7  * exports this variable to GPL modules.
   8  *
   9  * Copyright (C) 2013 Mentor Graphics Corp.
  10  */
  11
  12 #ifndef _LTTNG_WRAPPER_WRITEBACK_H
  13 #define _LTTNG_WRAPPER_WRITEBACK_H
  14
  15 #include <lttng/kernel-version.h>
  16
  17 #ifdef CONFIG_KALLSYMS_ALL
  18 #include <linux/kallsyms.h>
  19 #include <wrapper/kallsyms.h>
  20
  21
  22
  23 #if LINUX_VERSION_CODE >= KERNEL_VERSION(4,2,0)
  24
  25 static struct wb_domain *global_wb_domain_sym;
  26
  27 static inline
  28 unsigned long wrapper_global_dirty_limit(void)
  29 {
  30         if (!global_wb_domain_sym)
  31                 global_wb_domain_sym =
  32                         (void *) kallsyms_lookup_dataptr("global_wb_domain");
  33         if (global_wb_domain_sym) {
  34                 return global_wb_domain_sym->dirty_limit;
  35         } else {
  36                 printk_once(KERN_WARNING "LTTng: global_wb_domain symbol lookup failed.\n");
  37                 return 0;
  38         }
  39 }
  40 #else
  41
  42 static unsigned long *global_dirty_limit_sym;
  43
  44 static inline
  45 unsigned long wrapper_global_dirty_limit(void)
  46 {
  47         if (!global_dirty_limit_sym)
  48                 global_dirty_limit_sym =
  49                         (void *) kallsyms_lookup_dataptr("global_dirty_limit");
  50         if (global_dirty_limit_sym) {
  51                 return *global_dirty_limit_sym;
  52         } else {
  53                 printk_once(KERN_WARNING "LTTng: global_dirty_limit symbol lookup failed.\n");
  54                 return 0;
  55         }
  56 }
  57 #endif
  58
  59 #else /* CONFIG_KALLSYMS_ALL */
  60
  61 #include <linux/writeback.h>
  62
  63 static inline
  64 unsigned long wrapper_global_dirty_limit(void)
  65 {
  66         return global_dirty_limit;
  67 }
  68
  69 #endif
  70
  71 #endif /* _LTTNG_WRAPPER_WRITEBACK_H */