1 files changed, 73 insertions, 4 deletions

diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
index 58144102bf25..18bfd5dab642 100644
--- a/fs/jbd2/journal.c
+++ b/fs/jbd2/journal.c
@@ -38,6 +38,10 @@
 #include <linux/debugfs.h>
 #include <linux/seq_file.h>
 #include <linux/math64.h>
+#include <linux/hash.h>
+
+#define CREATE_TRACE_POINTS
+#include <trace/events/jbd2.h>
 
 #include <asm/uaccess.h>
 #include <asm/page.h>
@@ -1781,7 +1785,7 @@ int jbd2_journal_wipe(journal_t *journal, int write)
  * Journal abort has very specific semantics, which we describe
  * for journal abort.
  *
- * Two internal function, which provide abort to te jbd layer
+ * Two internal functions, which provide abort to the jbd layer
  * itself are here.
  */
 
@@ -1879,7 +1883,7 @@ void jbd2_journal_abort(journal_t *journal, int errno)
  * int jbd2_journal_errno () - returns the journal's error state.
  * @journal: journal to examine.
  *
- * This is the errno numbet set with jbd2_journal_abort(), the last
+ * This is the errno number set with jbd2_journal_abort(), the last
  * time the journal was mounted - if the journal was stopped
  * without calling abort this will be 0.
  *
@@ -1903,7 +1907,7 @@ int jbd2_journal_errno(journal_t *journal)
  * int jbd2_journal_clear_err () - clears the journal's error state
  * @journal: journal to act on.
  *
- * An error must be cleared or Acked to take a FS out of readonly
+ * An error must be cleared or acked to take a FS out of readonly
  * mode.
  */
 int jbd2_journal_clear_err(journal_t *journal)
@@ -1923,7 +1927,7 @@ int jbd2_journal_clear_err(journal_t *journal)
  * void jbd2_journal_ack_err() - Ack journal err.
  * @journal: journal to act on.
  *
- * An error must be cleared or Acked to take a FS out of readonly
+ * An error must be cleared or acked to take a FS out of readonly
  * mode.
  */
 void jbd2_journal_ack_err(journal_t *journal)
@@ -2377,6 +2381,71 @@ static void __exit journal_exit(void)
         jbd2_journal_destroy_caches();
 }
 
+/* 
+ * jbd2_dev_to_name is a utility function used by the jbd2 and ext4 
+ * tracing infrastructure to map a dev_t to a device name.
+ *
+ * The caller should use rcu_read_lock() in order to make sure the
+ * device name stays valid until its done with it.  We use
+ * rcu_read_lock() as well to make sure we're safe in case the caller
+ * gets sloppy, and because rcu_read_lock() is cheap and can be safely
+ * nested.
+ */
+struct devname_cache {
+        struct rcu_head rcu;
+        dev_t           device;
+        char            devname[BDEVNAME_SIZE];
+};
+#define CACHE_SIZE_BITS 6
+static struct devname_cache *devcache[1 << CACHE_SIZE_BITS];
+static DEFINE_SPINLOCK(devname_cache_lock);
+
+static void free_devcache(struct rcu_head *rcu)
+{
+        kfree(rcu);
+}
+
+const char *jbd2_dev_to_name(dev_t device)
+{
+        int     i = hash_32(device, CACHE_SIZE_BITS);
+        char    *ret;
+        struct block_device *bd;
+
+        rcu_read_lock();
+        if (devcache[i] && devcache[i]->device == device) {
+                ret = devcache[i]->devname;
+                rcu_read_unlock();
+                return ret;
+        }
+        rcu_read_unlock();
+
+        spin_lock(&devname_cache_lock);
+        if (devcache[i]) {
+                if (devcache[i]->device == device) {
+                        ret = devcache[i]->devname;
+                        spin_unlock(&devname_cache_lock);
+                        return ret;
+                }
+                call_rcu(&devcache[i]->rcu, free_devcache);
+        }
+        devcache[i] = kmalloc(sizeof(struct devname_cache), GFP_KERNEL);
+        if (!devcache[i]) {
+                spin_unlock(&devname_cache_lock);
+                return "NODEV-ALLOCFAILURE"; /* Something non-NULL */
+        }
+        devcache[i]->device = device;
+        bd = bdget(device);
+        if (bd) {
+                bdevname(bd, devcache[i]->devname);
+                bdput(bd);
+        } else
+                __bdevname(device, devcache[i]->devname);
+        ret = devcache[i]->devname;
+        spin_unlock(&devname_cache_lock);
+        return ret;
+}
+EXPORT_SYMBOL(jbd2_dev_to_name);
+
 MODULE_LICENSE("GPL");
 module_init(journal_init);
 module_exit(journal_exit);