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>

4 files changed, 19 insertions, 347 deletions

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index b491576e11c3..c508cf7be75c 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -65,6 +65,12 @@ typedef __u32 ext4_lblk_t;
 /* data type for block group number */
 typedef unsigned int ext4_group_t;
 
+/*
+ * Flags used in mballoc's allocation_context flags field.  
+ *
+ * Also used to show what's going on for debugging purposes when the
+ * flag field is exported via the traceport interface
+ */
 
 /* prefer goal again. length */
 #define EXT4_MB_HINT_MERGE              0x0001
@@ -971,14 +977,6 @@ struct ext4_sb_info {
         unsigned long s_mb_last_group;
         unsigned long s_mb_last_start;
 
-        /* history to debug policy */
-        struct ext4_mb_history *s_mb_history;
-        int s_mb_history_cur;
-        int s_mb_history_max;
-        int s_mb_history_num;
-        spinlock_t s_mb_history_lock;
-        int s_mb_history_filter;
-
         /* stats for buddy allocator */
         spinlock_t s_mb_pa_lock;
         atomic_t s_bal_reqs;    /* number of reqs with len > 1 */
diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 3e2320e66721..bba12824defa 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -2096,207 +2096,6 @@ out:
         return err;
 }
 
-#ifdef EXT4_MB_HISTORY
-struct ext4_mb_proc_session {
-        struct ext4_mb_history *history;
-        struct super_block *sb;
-        int start;
-        int max;
-};
-
-static void *ext4_mb_history_skip_empty(struct ext4_mb_proc_session *s,
-                                        struct ext4_mb_history *hs,
-                                        int first)
-{
-        if (hs == s->history + s->max)
-                hs = s->history;
-        if (!first && hs == s->history + s->start)
-                return NULL;
-        while (hs->orig.fe_len == 0) {
-                hs++;
-                if (hs == s->history + s->max)
-                        hs = s->history;
-                if (hs == s->history + s->start)
-                        return NULL;
-        }
-        return hs;
-}
-
-static void *ext4_mb_seq_history_start(struct seq_file *seq, loff_t *pos)
-{
-        struct ext4_mb_proc_session *s = seq->private;
-        struct ext4_mb_history *hs;
-        int l = *pos;
-
-        if (l == 0)
-                return SEQ_START_TOKEN;
-        hs = ext4_mb_history_skip_empty(s, s->history + s->start, 1);
-        if (!hs)
-                return NULL;
-        while (--l && (hs = ext4_mb_history_skip_empty(s, ++hs, 0)) != NULL);
-        return hs;
-}
-
-static void *ext4_mb_seq_history_next(struct seq_file *seq, void *v,
-                                      loff_t *pos)
-{
-        struct ext4_mb_proc_session *s = seq->private;
-        struct ext4_mb_history *hs = v;
-
-        ++*pos;
-        if (v == SEQ_START_TOKEN)
-                return ext4_mb_history_skip_empty(s, s->history + s->start, 1);
-        else
-                return ext4_mb_history_skip_empty(s, ++hs, 0);
-}
-
-static int ext4_mb_seq_history_show(struct seq_file *seq, void *v)
-{
-        char buf[25], buf2[25], buf3[25], *fmt;
-        struct ext4_mb_history *hs = v;
-
-        if (v == SEQ_START_TOKEN) {
-                seq_printf(seq, "%-5s %-8s %-23s %-23s %-23s %-5s "
-                                "%-5s %-2s %-6s %-5s %-5s %-6s\n",
-                          "pid", "inode", "original", "goal", "result", "found",
-                           "grps", "cr", "flags", "merge", "tail", "broken");
-                return 0;
-        }
-
-        if (hs->op == EXT4_MB_HISTORY_ALLOC) {
-                fmt = "%-5u %-8u %-23s %-23s %-23s %-5u %-5u %-2u "
-                        "0x%04x %-5s %-5u %-6u\n";
-                sprintf(buf2, "%u/%d/%u@%u", hs->result.fe_group,
-                        hs->result.fe_start, hs->result.fe_len,
-                        hs->result.fe_logical);
-                sprintf(buf, "%u/%d/%u@%u", hs->orig.fe_group,
-                        hs->orig.fe_start, hs->orig.fe_len,
-                        hs->orig.fe_logical);
-                sprintf(buf3, "%u/%d/%u@%u", hs->goal.fe_group,
-                        hs->goal.fe_start, hs->goal.fe_len,
-                        hs->goal.fe_logical);
-                seq_printf(seq, fmt, hs->pid, hs->ino, buf, buf3, buf2,
-                                hs->found, hs->groups, hs->cr, hs->flags,
-                                hs->merged ? "M" : "", hs->tail,
-                                hs->buddy ? 1 << hs->buddy : 0);
-        } else if (hs->op == EXT4_MB_HISTORY_PREALLOC) {
-                fmt = "%-5u %-8u %-23s %-23s %-23s\n";
-                sprintf(buf2, "%u/%d/%u@%u", hs->result.fe_group,
-                        hs->result.fe_start, hs->result.fe_len,
-                        hs->result.fe_logical);
-                sprintf(buf, "%u/%d/%u@%u", hs->orig.fe_group,
-                        hs->orig.fe_start, hs->orig.fe_len,
-                        hs->orig.fe_logical);
-                seq_printf(seq, fmt, hs->pid, hs->ino, buf, "", buf2);
-        } else if (hs->op == EXT4_MB_HISTORY_DISCARD) {
-                sprintf(buf2, "%u/%d/%u", hs->result.fe_group,
-                        hs->result.fe_start, hs->result.fe_len);
-                seq_printf(seq, "%-5u %-8u %-23s discard\n",
-                                hs->pid, hs->ino, buf2);
-        } else if (hs->op == EXT4_MB_HISTORY_FREE) {
-                sprintf(buf2, "%u/%d/%u", hs->result.fe_group,
-                        hs->result.fe_start, hs->result.fe_len);
-                seq_printf(seq, "%-5u %-8u %-23s free\n",
-                                hs->pid, hs->ino, buf2);
-        }
-        return 0;
-}
-
-static void ext4_mb_seq_history_stop(struct seq_file *seq, void *v)
-{
-}
-
-static const struct seq_operations ext4_mb_seq_history_ops = {
-        .start  = ext4_mb_seq_history_start,
-        .next   = ext4_mb_seq_history_next,
-        .stop   = ext4_mb_seq_history_stop,
-        .show   = ext4_mb_seq_history_show,
-};
-
-static int ext4_mb_seq_history_open(struct inode *inode, struct file *file)
-{
-        struct super_block *sb = PDE(inode)->data;
-        struct ext4_sb_info *sbi = EXT4_SB(sb);
-        struct ext4_mb_proc_session *s;
-        int rc;
-        int size;
-
-        if (unlikely(sbi->s_mb_history == NULL))
-                return -ENOMEM;
-        s = kmalloc(sizeof(*s), GFP_KERNEL);
-        if (s == NULL)
-                return -ENOMEM;
-        s->sb = sb;
-        size = sizeof(struct ext4_mb_history) * sbi->s_mb_history_max;
-        s->history = kmalloc(size, GFP_KERNEL);
-        if (s->history == NULL) {
-                kfree(s);
-                return -ENOMEM;
-        }
-
-        spin_lock(&sbi->s_mb_history_lock);
-        memcpy(s->history, sbi->s_mb_history, size);
-        s->max = sbi->s_mb_history_max;
-        s->start = sbi->s_mb_history_cur % s->max;
-        spin_unlock(&sbi->s_mb_history_lock);
-
-        rc = seq_open(file, &ext4_mb_seq_history_ops);
-        if (rc == 0) {
-                struct seq_file *m = (struct seq_file *)file->private_data;
-                m->private = s;
-        } else {
-                kfree(s->history);
-                kfree(s);
-        }
-        return rc;
-
-}
-
-static int ext4_mb_seq_history_release(struct inode *inode, struct file *file)
-{
-        struct seq_file *seq = (struct seq_file *)file->private_data;
-        struct ext4_mb_proc_session *s = seq->private;
-        kfree(s->history);
-        kfree(s);
-        return seq_release(inode, file);
-}
-
-static ssize_t ext4_mb_seq_history_write(struct file *file,
-                                const char __user *buffer,
-                                size_t count, loff_t *ppos)
-{
-        struct seq_file *seq = (struct seq_file *)file->private_data;
-        struct ext4_mb_proc_session *s = seq->private;
-        struct super_block *sb = s->sb;
-        char str[32];
-        int value;
-
-        if (count >= sizeof(str)) {
-                printk(KERN_ERR "EXT4-fs: %s string too long, max %u bytes\n",
-                                "mb_history", (int)sizeof(str));
-                return -EOVERFLOW;
-        }
-
-        if (copy_from_user(str, buffer, count))
-                return -EFAULT;
-
-        value = simple_strtol(str, NULL, 0);
-        if (value < 0)
-                return -ERANGE;
-        EXT4_SB(sb)->s_mb_history_filter = value;
-
-        return count;
-}
-
-static const struct file_operations ext4_mb_seq_history_fops = {
-        .owner          = THIS_MODULE,
-        .open           = ext4_mb_seq_history_open,
-        .read           = seq_read,
-        .write          = ext4_mb_seq_history_write,
-        .llseek         = seq_lseek,
-        .release        = ext4_mb_seq_history_release,
-};
-
 static void *ext4_mb_seq_groups_start(struct seq_file *seq, loff_t *pos)
 {
         struct super_block *sb = seq->private;
@@ -2396,82 +2195,6 @@ static const struct file_operations ext4_mb_seq_groups_fops = {
         .release        = seq_release,
 };
 
-static void ext4_mb_history_release(struct super_block *sb)
-{
-        struct ext4_sb_info *sbi = EXT4_SB(sb);
-
-        if (sbi->s_proc != NULL) {
-                remove_proc_entry("mb_groups", sbi->s_proc);
-                if (sbi->s_mb_history_max)
-                        remove_proc_entry("mb_history", sbi->s_proc);
-        }
-        kfree(sbi->s_mb_history);
-}
-
-static void ext4_mb_history_init(struct super_block *sb)
-{
-        struct ext4_sb_info *sbi = EXT4_SB(sb);
-        int i;
-
-        if (sbi->s_proc != NULL) {
-                if (sbi->s_mb_history_max)
-                        proc_create_data("mb_history", S_IRUGO, sbi->s_proc,
-                                         &ext4_mb_seq_history_fops, sb);
-                proc_create_data("mb_groups", S_IRUGO, sbi->s_proc,
-                                 &ext4_mb_seq_groups_fops, sb);
-        }
-
-        sbi->s_mb_history_cur = 0;
-        spin_lock_init(&sbi->s_mb_history_lock);
-        i = sbi->s_mb_history_max * sizeof(struct ext4_mb_history);
-        sbi->s_mb_history = i ? kzalloc(i, GFP_KERNEL) : NULL;
-        /* if we can't allocate history, then we simple won't use it */
-}
-
-static noinline_for_stack void
-ext4_mb_store_history(struct ext4_allocation_context *ac)
-{
-        struct ext4_sb_info *sbi = EXT4_SB(ac->ac_sb);
-        struct ext4_mb_history h;
-
-        if (sbi->s_mb_history == NULL)
-                return;
-
-        if (!(ac->ac_op & sbi->s_mb_history_filter))
-                return;
-
-        h.op = ac->ac_op;
-        h.pid = current->pid;
-        h.ino = ac->ac_inode ? ac->ac_inode->i_ino : 0;
-        h.orig = ac->ac_o_ex;
-        h.result = ac->ac_b_ex;
-        h.flags = ac->ac_flags;
-        h.found = ac->ac_found;
-        h.groups = ac->ac_groups_scanned;
-        h.cr = ac->ac_criteria;
-        h.tail = ac->ac_tail;
-        h.buddy = ac->ac_buddy;
-        h.merged = 0;
-        if (ac->ac_op == EXT4_MB_HISTORY_ALLOC) {
-                if (ac->ac_g_ex.fe_start == ac->ac_b_ex.fe_start &&
-                                ac->ac_g_ex.fe_group == ac->ac_b_ex.fe_group)
-                        h.merged = 1;
-                h.goal = ac->ac_g_ex;
-                h.result = ac->ac_f_ex;
-        }
-
-        spin_lock(&sbi->s_mb_history_lock);
-        memcpy(sbi->s_mb_history + sbi->s_mb_history_cur, &h, sizeof(h));
-        if (++sbi->s_mb_history_cur >= sbi->s_mb_history_max)
-                sbi->s_mb_history_cur = 0;
-        spin_unlock(&sbi->s_mb_history_lock);
-}
-
-#else
-#define ext4_mb_history_release(sb)
-#define ext4_mb_history_init(sb)
-#endif
-
 
 /* Create and initialize ext4_group_info data for the given group. */
 int ext4_mb_add_groupinfo(struct super_block *sb, ext4_group_t group,
@@ -2690,7 +2413,6 @@ int ext4_mb_init(struct super_block *sb, int needs_recovery)
         sbi->s_mb_stats = MB_DEFAULT_STATS;
         sbi->s_mb_stream_request = MB_DEFAULT_STREAM_THRESHOLD;
         sbi->s_mb_order2_reqs = MB_DEFAULT_ORDER2_REQS;
-        sbi->s_mb_history_filter = EXT4_MB_HISTORY_DEFAULT;
         sbi->s_mb_group_prealloc = MB_DEFAULT_GROUP_PREALLOC;
 
         sbi->s_locality_groups = alloc_percpu(struct ext4_locality_group);
@@ -2708,7 +2430,9 @@ int ext4_mb_init(struct super_block *sb, int needs_recovery)
                 spin_lock_init(&lg->lg_prealloc_lock);
         }
 
-        ext4_mb_history_init(sb);
+        if (sbi->s_proc)
+                proc_create_data("mb_groups", S_IRUGO, sbi->s_proc,
+                                 &ext4_mb_seq_groups_fops, sb);
 
         if (sbi->s_journal)
                 sbi->s_journal->j_commit_callback = release_blocks_on_commit;
@@ -2788,7 +2512,8 @@ int ext4_mb_release(struct super_block *sb)
         }
 
         free_percpu(sbi->s_locality_groups);
-        ext4_mb_history_release(sb);
+        if (sbi->s_proc)
+                remove_proc_entry("mb_groups", sbi->s_proc);
 
         return 0;
 }
@@ -3274,7 +2999,10 @@ static void ext4_mb_collect_stats(struct ext4_allocation_context *ac)
                         atomic_inc(&sbi->s_bal_breaks);
         }
 
-        ext4_mb_store_history(ac);
+        if (ac->ac_op == EXT4_MB_HISTORY_ALLOC)
+                trace_ext4_mballoc_alloc(ac);
+        else
+                trace_ext4_mballoc_prealloc(ac);
 }
 
 /*
@@ -3774,7 +3502,6 @@ ext4_mb_release_inode_pa(struct ext4_buddy *e4b, struct buffer_head *bitmap_bh,
         if (ac) {
                 ac->ac_sb = sb;
                 ac->ac_inode = pa->pa_inode;
-                ac->ac_op = EXT4_MB_HISTORY_DISCARD;
         }
 
         while (bit < end) {
@@ -3794,7 +3521,7 @@ ext4_mb_release_inode_pa(struct ext4_buddy *e4b, struct buffer_head *bitmap_bh,
                         ac->ac_b_ex.fe_start = bit;
                         ac->ac_b_ex.fe_len = next - bit;
                         ac->ac_b_ex.fe_logical = 0;
-                        ext4_mb_store_history(ac);
+                        trace_ext4_mballoc_discard(ac);
                 }
 
                 trace_ext4_mb_release_inode_pa(ac, pa, grp_blk_start + bit,
@@ -3829,9 +3556,6 @@ ext4_mb_release_group_pa(struct ext4_buddy *e4b,
         ext4_group_t group;
         ext4_grpblk_t bit;
 
-        if (ac)
-                ac->ac_op = EXT4_MB_HISTORY_DISCARD;
-
         trace_ext4_mb_release_group_pa(ac, pa);
         BUG_ON(pa->pa_deleted == 0);
         ext4_get_group_no_and_offset(sb, pa->pa_pstart, &group, &bit);
@@ -3846,7 +3570,7 @@ ext4_mb_release_group_pa(struct ext4_buddy *e4b,
                 ac->ac_b_ex.fe_start = bit;
                 ac->ac_b_ex.fe_len = pa->pa_len;
                 ac->ac_b_ex.fe_logical = 0;
-                ext4_mb_store_history(ac);
+                trace_ext4_mballoc_discard(ac);
         }
 
         return 0;
@@ -4737,7 +4461,6 @@ void ext4_mb_free_blocks(handle_t *handle, struct inode *inode,
 
         ac = kmem_cache_alloc(ext4_ac_cachep, GFP_NOFS);
         if (ac) {
-                ac->ac_op = EXT4_MB_HISTORY_FREE;
                 ac->ac_inode = inode;
                 ac->ac_sb = sb;
         }
@@ -4804,7 +4527,7 @@ do_more:
                 ac->ac_b_ex.fe_group = block_group;
                 ac->ac_b_ex.fe_start = bit;
                 ac->ac_b_ex.fe_len = count;
-                ext4_mb_store_history(ac);
+                trace_ext4_mballoc_free(ac);
         }
 
         err = ext4_mb_load_buddy(sb, block_group, &e4b);
diff --git a/fs/ext4/mballoc.h b/fs/ext4/mballoc.h
index 14f25f253112..0ca811061bc7 100644
--- a/fs/ext4/mballoc.h
+++ b/fs/ext4/mballoc.h
@@ -52,18 +52,8 @@ extern u8 mb_enable_debug;
 #define mb_debug(n, fmt, a...)
 #endif
 
-/*
- * with EXT4_MB_HISTORY mballoc stores last N allocations in memory
- * and you can monitor it in /proc/fs/ext4/<dev>/mb_history
- */
-#define EXT4_MB_HISTORY
 #define EXT4_MB_HISTORY_ALLOC           1       /* allocation */
 #define EXT4_MB_HISTORY_PREALLOC        2       /* preallocated blocks used */
-#define EXT4_MB_HISTORY_DISCARD         4       /* preallocation discarded */
-#define EXT4_MB_HISTORY_FREE            8       /* free */
-
-#define EXT4_MB_HISTORY_DEFAULT         (EXT4_MB_HISTORY_ALLOC | \
-                                         EXT4_MB_HISTORY_PREALLOC)
 
 /*
  * How long mballoc can look for a best extent (in found extents)
@@ -217,22 +207,6 @@ struct ext4_allocation_context {
 #define AC_STATUS_FOUND         2
 #define AC_STATUS_BREAK         3
 
-struct ext4_mb_history {
-        struct ext4_free_extent orig;   /* orig allocation */
-        struct ext4_free_extent goal;   /* goal allocation */
-        struct ext4_free_extent result; /* result allocation */
-        unsigned pid;
-        unsigned ino;
-        __u16 found;    /* how many extents have been found */
-        __u16 groups;   /* how many groups have been scanned */
-        __u16 tail;     /* what tail broke some buddy */
-        __u16 buddy;    /* buddy the tail ^^^ broke */
-        __u16 flags;
-        __u8 cr:3;      /* which phase the result extent was found at */
-        __u8 op:4;
-        __u8 merged:1;
-};
-
 struct ext4_buddy {
         struct page *bd_buddy_page;
         void *bd_buddy;
@@ -247,13 +221,6 @@ struct ext4_buddy {
 #define EXT4_MB_BITMAP(e4b)     ((e4b)->bd_bitmap)
 #define EXT4_MB_BUDDY(e4b)      ((e4b)->bd_buddy)
 
-#ifndef EXT4_MB_HISTORY
-static inline void ext4_mb_store_history(struct ext4_allocation_context *ac)
-{
-        return;
-}
-#endif
-
 #define in_range(b, first, len) ((b) >= (first) && (b) <= (first) + (len) - 1)
 
 static inline ext4_fsblk_t ext4_grp_offs_to_block(struct super_block *sb,
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);