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 b491576e11c..c508cf7be75 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 3e2320e6672..bba12824def 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 14f25f25311..0ca811061bc 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 e5b206a043a..12e726a7073 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);