mm/mmap_lock.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 #define CREATE_TRACE_POINTS
   3 #include <trace/events/mmap_lock.h>
   4
   5 #include <linux/mm.h>
   6 #include <linux/cgroup.h>
   7 #include <linux/memcontrol.h>
   8 #include <linux/mmap_lock.h>
   9 #include <linux/mutex.h>
  10 #include <linux/percpu.h>
  11 #include <linux/rcupdate.h>
  12 #include <linux/smp.h>
  13 #include <linux/trace_events.h>
  14 #include <linux/local_lock.h>
  15
  16 EXPORT_TRACEPOINT_SYMBOL(mmap_lock_start_locking);
  17 EXPORT_TRACEPOINT_SYMBOL(mmap_lock_acquire_returned);
  18 EXPORT_TRACEPOINT_SYMBOL(mmap_lock_released);
  19
  20 #ifdef CONFIG_MEMCG
  21
  22 static atomic_t reg_refcount;
  23
  24 /*
  25  * Size of the buffer for memcg path names. Ignoring stack trace support,
  26  * trace_events_hist.c uses MAX_FILTER_STR_VAL for this, so we also use it.
  27  */
  28 #define MEMCG_PATH_BUF_SIZE MAX_FILTER_STR_VAL
  29
  30 int trace_mmap_lock_reg(void)
  31 {
  32         atomic_inc(&reg_refcount);
  33         return 0;
  34 }
  35
  36 void trace_mmap_lock_unreg(void)
  37 {
  38         atomic_dec(&reg_refcount);
  39 }
  40
  41 #define TRACE_MMAP_LOCK_EVENT(type, mm, ...)                    \
  42         do {                                                    \
  43                 char buf[MEMCG_PATH_BUF_SIZE];                  \
  44                 get_mm_memcg_path(mm, buf, sizeof(buf));        \
  45                 trace_mmap_lock_##type(mm, buf, ##__VA_ARGS__); \
  46         } while (0)
  47
  48 #else /* !CONFIG_MEMCG */
  49
  50 int trace_mmap_lock_reg(void)
  51 {
  52         return 0;
  53 }
  54
  55 void trace_mmap_lock_unreg(void)
  56 {
  57 }
  58
  59 #define TRACE_MMAP_LOCK_EVENT(type, mm, ...)                                   \
  60         trace_mmap_lock_##type(mm, "", ##__VA_ARGS__)
  61
  62 #endif /* CONFIG_MEMCG */
  63
  64 #ifdef CONFIG_TRACING
  65 #ifdef CONFIG_MEMCG
  66 /*
  67  * Write the given mm_struct's memcg path to a buffer. If the path cannot be
  68  * determined or the trace event is being unregistered, empty string is written.
  69  */
  70 static void get_mm_memcg_path(struct mm_struct *mm, char *buf, size_t buflen)
  71 {
  72         struct mem_cgroup *memcg;
  73
  74         buf[0] = '\0';
  75         /* No need to get path if no trace event is registered. */
  76         if (!atomic_read(&reg_refcount))
  77                 return;
  78         memcg = get_mem_cgroup_from_mm(mm);
  79         if (memcg == NULL)
  80                 return;
  81         if (memcg->css.cgroup)
  82                 cgroup_path(memcg->css.cgroup, buf, buflen);
  83         css_put(&memcg->css);
  84 }
  85
  86 #endif /* CONFIG_MEMCG */
  87
  88 /*
  89  * Trace calls must be in a separate file, as otherwise there's a circular
  90  * dependency between linux/mmap_lock.h and trace/events/mmap_lock.h.
  91  */
  92
  93 void __mmap_lock_do_trace_start_locking(struct mm_struct *mm, bool write)
  94 {
  95         TRACE_MMAP_LOCK_EVENT(start_locking, mm, write);
  96 }
  97 EXPORT_SYMBOL(__mmap_lock_do_trace_start_locking);
  98
  99 void __mmap_lock_do_trace_acquire_returned(struct mm_struct *mm, bool write,
 100                                            bool success)
 101 {
 102         TRACE_MMAP_LOCK_EVENT(acquire_returned, mm, write, success);
 103 }
 104 EXPORT_SYMBOL(__mmap_lock_do_trace_acquire_returned);
 105
 106 void __mmap_lock_do_trace_released(struct mm_struct *mm, bool write)
 107 {
 108         TRACE_MMAP_LOCK_EVENT(released, mm, write);
 109 }
 110 EXPORT_SYMBOL(__mmap_lock_do_trace_released);
 111 #endif /* CONFIG_TRACING */