ext4: Use tracepoints for mb_history trace file

The /proc/fs/ext4/<dev>/mb_history was maintained manually, and had a
number of problems: it required a largish amount of memory to be
allocated for each ext4 filesystem, and the s_mb_history_lock
introduced a CPU contention problem.  

By ripping out the mb_history code and replacing it with ftrace
tracepoints, and we get more functionality: timestamps, event
filtering, the ability to correlate mballoc history with other ext4
tracepoints, etc.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

1 files changed, 1 insertions, 17 deletions

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index e5b206a043a5..12e726a7073f 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -50,13 +50,6 @@
 #define CREATE_TRACE_POINTS
 #include <trace/events/ext4.h>
 
-static int default_mb_history_length = 1000;
-
-module_param_named(default_mb_history_length, default_mb_history_length,
-                   int, 0644);
-MODULE_PARM_DESC(default_mb_history_length,
-                 "Default number of entries saved for mb_history");
-
 struct proc_dir_entry *ext4_proc_root;
 static struct kset *ext4_kset;
 
@@ -1079,7 +1072,7 @@ enum {
         Opt_journal_update, Opt_journal_dev,
         Opt_journal_checksum, Opt_journal_async_commit,
         Opt_abort, Opt_data_journal, Opt_data_ordered, Opt_data_writeback,
-        Opt_data_err_abort, Opt_data_err_ignore, Opt_mb_history_length,
+        Opt_data_err_abort, Opt_data_err_ignore,
         Opt_usrjquota, Opt_grpjquota, Opt_offusrjquota, Opt_offgrpjquota,
         Opt_jqfmt_vfsold, Opt_jqfmt_vfsv0, Opt_quota, Opt_noquota,
         Opt_ignore, Opt_barrier, Opt_nobarrier, Opt_err, Opt_resize,
@@ -1126,7 +1119,6 @@ static const match_table_t tokens = {
         {Opt_data_writeback, "data=writeback"},
         {Opt_data_err_abort, "data_err=abort"},
         {Opt_data_err_ignore, "data_err=ignore"},
-        {Opt_mb_history_length, "mb_history_length=%u"},
         {Opt_offusrjquota, "usrjquota="},
         {Opt_usrjquota, "usrjquota=%s"},
         {Opt_offgrpjquota, "grpjquota="},
@@ -1367,13 +1359,6 @@ static int parse_options(char *options, struct super_block *sb,
                 case Opt_data_err_ignore:
                         clear_opt(sbi->s_mount_opt, DATA_ERR_ABORT);
                         break;
-                case Opt_mb_history_length:
-                        if (match_int(&args[0], &option))
-                                return 0;
-                        if (option < 0)
-                                return 0;
-                        sbi->s_mb_history_max = option;
-                        break;
 #ifdef CONFIG_QUOTA
                 case Opt_usrjquota:
                         qtype = USRQUOTA;
@@ -2435,7 +2420,6 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
         sbi->s_commit_interval = JBD2_DEFAULT_MAX_COMMIT_AGE * HZ;
         sbi->s_min_batch_time = EXT4_DEF_MIN_BATCH_TIME;
         sbi->s_max_batch_time = EXT4_DEF_MAX_BATCH_TIME;
-        sbi->s_mb_history_max = default_mb_history_length;
 
         set_opt(sbi->s_mount_opt, BARRIER);