Perf can't deal with many tracepoints

Perf can't deal with many tracepoints

[Theodore Ts'o]

Perf will drop dead if it comes across tracepoints that have anything
but primitive structure accessors in the TP_printk() section of the
tracepoint definition.  For example, the ext4 and jbd2 tracepoints uses
jbd2_dev_to_name() to translate a dev_t to a string.  The block I/O
tracepoints uses MAJOR() and MINOR() to translate a dev_t to a
major/minor number pair.  Both do this in TP_printk.  This results in a
fatal error:

# perf record -R -c 1 -e ext4:ext4_da_writepages sh -c "cp -r /boot /test; sync"
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.110 MB perf.data (~4786 samples) ]
# perf trace -i perf.data
  Fatal: no argument match
              cp-9792   [007] 1181919.509759: ext4_da_writepages: dev jbd2_dev_to_name ino

There are people roaming around trying to convince me that perf is the
One True Way to do everything, including tracepoints.  But there are a
whole bunch of tracepoints that perf can't handle.  It seems to me we
have three possible solutions:

1) Accept there are some tracepoints perf just can't handle, and just
say that ftrace is the only way people can use those tracepoints

2) Enforce a rule which says that nothing other than primitive structure
accessors are allowed, in which case we need a patch such like the one
attached.  (We will need to audit all tracepoints; it's more than just
ext4, as I've mentioned --- and yes, the patch below is ugly.  But it
may be what I have to do to accomodate perf --- or maybe I should just
tell people that perf is not supported, and if you want to use ext4 or
block I/O tracepoints, you should use ftrace?)

3) Figure out some way of making perf smarter; I don't know how to do
that in the general case, since it can't handle arbitrary C statements.
But maybe it could be taught how to handle dev_t's in some intelligent
fashion, perhaps.  And then combine this with either (1) or (2) above.

What say ye?

						- Ted

commit 6e0312bf2ff174ea861e5c5436f87660963ade8d
Author: Theodore Ts'o <tytso@mit.edu>
Date:   Wed Oct 27 18:59:25 2010 -0400

    ext4,jbd2: Convert tracepoints to use major/minor numbers
    
    Unfortunately perf can't deal with anything other than direct structure
    accesses in the TP_printk() section.  It will drop dead when it sees
    jbd2_dev_to_name() in the "print fmt" section of the tracepoint.
    
    Addresses-Google-Bug: 3138508
    
    Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

diff --git a/include/trace/events/ext4.h b/include/trace/events/ext4.h
index b5f4938..8f59db1 100644
--- a/include/trace/events/ext4.h
+++ b/include/trace/events/ext4.h
@@ -21,7 +21,8 @@ TRACE_EVENT(ext4_free_inode,
 	TP_ARGS(inode),
 
 	TP_STRUCT__entry(
-		__field(	dev_t,	dev			)
+		__field(	int,   dev_major                )
+		__field(	int,   dev_minor                )
 		__field(	ino_t,	ino			)
 		__field(	umode_t, mode			)
 		__field(	uid_t,	uid			)
@@ -30,7 +31,8 @@ TRACE_EVENT(ext4_free_inode,
 	),
 
 	TP_fast_assign(
-		__entry->dev	= inode->i_sb->s_dev;
+		__entry->dev_major = MAJOR(inode->i_sb->s_dev);
+		__entry->dev_minor = MINOR(inode->i_sb->s_dev);
 		__entry->ino	= inode->i_ino;
 		__entry->mode	= inode->i_mode;
 		__entry->uid	= inode->i_uid;
@@ -38,9 +40,10 @@ TRACE_EVENT(ext4_free_inode,
 		__entry->blocks	= inode->i_blocks;
 	),
 
-	TP_printk("dev %s ino %lu mode 0%o uid %u gid %u blocks %llu",
-		  jbd2_dev_to_name(__entry->dev), (unsigned long) __entry->ino,
-		  __entry->mode, __entry->uid, __entry->gid,
+	TP_printk("dev %d,%d ino %lu mode 0%o uid %u gid %u blocks %llu",
+		  __entry->dev_major, __entry->dev_minor,
+		  (unsigned long) __entry->ino, __entry->mode,
+		  __entry->uid, __entry->gid,
 		  (unsigned long long) __entry->blocks)
 );
 
@@ -50,20 +53,22 @@ TRACE_EVENT(ext4_request_inode,
 	TP_ARGS(dir, mode),
 
 	TP_STRUCT__entry(
-		__field(	dev_t,	dev			)
+		__field(	int,   dev_major                )
+		__field(	int,   dev_minor                )
 		__field(	ino_t,	dir			)
 		__field(	umode_t, mode			)
 	),
 
 	TP_fast_assign(
-		__entry->dev	= dir->i_sb->s_dev;
+		__entry->dev_major = MAJOR(dir->i_sb->s_dev);
+		__entry->dev_minor = MINOR(dir->i_sb->s_dev);
 		__entry->dir	= dir->i_ino;
 		__entry->mode	= mode;
 	),
 
-	TP_printk("dev %s dir %lu mode 0%o",
-		  jbd2_dev_to_name(__entry->dev), (unsigned long) __entry->dir,
-		  __entry->mode)
+	TP_printk("dev %d,%d dir %lu mode 0%o",
+		  __entry->dev_major, __entry->dev_minor,
+		  (unsigned long) __entry->dir, __entry->mode)
 );
 
 TRACE_EVENT(ext4_allocate_inode,
@@ -72,21 +77,24 @@ TRACE_EVENT(ext4_allocate_inode,
 	TP_ARGS(inode, dir, mode),
 
 	TP_STRUCT__entry(
-		__field(	dev_t,	dev			)
+		__field(	int,   dev_major                )
+		__field(	int,   dev_minor                )
 		__field(	ino_t,	ino			)
 		__field(	ino_t,	dir			)
 		__field(	umode_t, mode			)
 	),
 
 	TP_fast_assign(
-		__entry->dev	= inode->i_sb->s_dev;
+		__entry->dev_major = MAJOR(inode->i_sb->s_dev);
+		__entry->dev_minor = MINOR(inode->i_sb->s_dev);
 		__entry->ino	= inode->i_ino;
 		__entry->dir	= dir->i_ino;
 		__entry->mode	= mode;
 	),
 
-	TP_printk("dev %s ino %lu dir %lu mode 0%o",
-		  jbd2_dev_to_name(__entry->dev), (unsigned long) __entry->ino,
+	TP_printk("dev %d,%d ino %lu dir %lu mode 0%o",
+		  __entry->dev_major, __entry->dev_minor,
+		  (unsigned long) __entry->ino,
 		  (unsigned long) __entry->dir, __entry->mode)
 );
 
@@ -98,7 +106,8 @@ DECLARE_EVENT_CLASS(ext4__write_begin,
 	TP_ARGS(inode, pos, len, flags),
 
 	TP_STRUCT__entry(
-		__field(	dev_t,	dev			)
+		__field(	int,   dev_major                )
+		__field(	int,   dev_minor                )
 		__field(	ino_t,	ino			)
 		__field(	loff_t,	pos			)
 		__field(	unsigned int, len		)
@@ -106,15 +115,17 @@ DECLARE_EVENT_CLASS(ext4__write_begin,
 	),
 
 	TP_fast_assign(
-		__entry->dev	= inode->i_sb->s_dev;
+		__entry->dev_major = MAJOR(inode->i_sb->s_dev);
+		__entry->dev_minor = MINOR(inode->i_sb->s_dev);
 		__entry->ino	= inode->i_ino;
 		__entry->pos	= pos;
 		__entry->len	= len;
 		__entry->flags	= flags;
 	),
 
-	TP_printk("dev %s ino %lu pos %llu len %u flags %u",
-		  jbd2_dev_to_name(__entry->dev), (unsigned long) __entry->ino,
+	TP_printk("dev %d,%d ino %lu pos %llu len %u flags %u",
+		  __entry->dev_major, __entry->dev_minor,
+		  (unsigned long) __entry->ino,
 		  __entry->pos, __entry->len, __entry->flags)
 );
 
@@ -141,7 +152,8 @@ DECLARE_EVENT_CLASS(ext4__write_end,
 	TP_ARGS(inode, pos, len, copied),
 
 	TP_STRUCT__entry(
-		__field(	dev_t,	dev			)
+		__field(	int,   dev_major                )
+		__field(	int,   dev_minor                )
 		__field(	ino_t,	ino			)
 		__field(	loff_t,	pos			)
 		__field(	unsigned int, len		)
@@ -149,16 +161,18 @@ DECLARE_EVENT_CLASS(ext4__write_end,
 	),
 
 	TP_fast_assign(
-		__entry->dev	= inode->i_sb->s_dev;
+		__entry->dev_major = MAJOR(inode->i_sb->s_dev);
+		__entry->dev_minor = MINOR(inode->i_sb->s_dev);
 		__entry->ino	= inode->i_ino;
 		__entry->pos	= pos;
 		__entry->len	= len;
 		__entry->copied	= copied;
 	),
 
-	TP_printk("dev %s ino %lu pos %llu len %u copied %u",
-		  jbd2_dev_to_name(__entry->dev), (unsigned long) __entry->ino,
-		  __entry->pos, __entry->len, __entry->copied)
+	TP_printk("dev %d,%d ino %lu pos %llu len %u copied %u",
+		  __entry->dev_major, __entry->dev_minor,
+		  (unsigned long) __entry->ino, __entry->pos,
+		  __entry->len, __entry->copied)
 );
 
 DEFINE_EVENT(ext4__write_end, ext4_ordered_write_end,
@@ -199,21 +213,23 @@ TRACE_EVENT(ext4_writepage,
 	TP_ARGS(inode, page),
 
 	TP_STRUCT__entry(
-		__field(	dev_t,	dev			)
+		__field(	int,   dev_major                )
+		__field(	int,   dev_minor                )
 		__field(	ino_t,	ino			)
 		__field(	pgoff_t, index			)
 
 	),
 
 	TP_fast_assign(
-		__entry->dev	= inode->i_sb->s_dev;
+		__entry->dev_major = MAJOR(inode->i_sb->s_dev);
+		__entry->dev_minor = MINOR(inode->i_sb->s_dev);
 		__entry->ino	= inode->i_ino;
 		__entry->index	= page->index;
 	),
 
-	TP_printk("dev %s ino %lu page_index %lu",
-		  jbd2_dev_to_name(__entry->dev), (unsigned long) __entry->ino,
-		  __entry->index)
+	TP_printk("dev %d,%d ino %lu page_index %lu",
+		  __entry->dev_major, __entry->dev_minor,
+		  (unsigned long) __entry->ino, __entry->index)
 );
 
 TRACE_EVENT(ext4_da_writepages,
@@ -222,7 +238,8 @@ TRACE_EVENT(ext4_da_writepages,
 	TP_ARGS(inode, wbc),
 
 	TP_STRUCT__entry(
-		__field(	dev_t,	dev			)
+		__field(	int,   dev_major                )
+		__field(	int,   dev_minor                )
 		__field(	ino_t,	ino			)
 		__field(	long,	nr_to_write		)
 		__field(	long,	pages_skipped		)
@@ -236,7 +253,8 @@ TRACE_EVENT(ext4_da_writepages,
 	),
 
 	TP_fast_assign(
-		__entry->dev		= inode->i_sb->s_dev;
+		__entry->dev_major	= MAJOR(inode->i_sb->s_dev);
+		__entry->dev_minor	= MINOR(inode->i_sb->s_dev);
 		__entry->ino		= inode->i_ino;
 		__entry->nr_to_write	= wbc->nr_to_write;
 		__entry->pages_skipped	= wbc->pages_skipped;
@@ -249,8 +267,8 @@ TRACE_EVENT(ext4_da_writepages,
 		__entry->writeback_index = inode->i_mapping->writeback_index;
 	),
 
-	TP_printk("dev %s ino %lu nr_to_write %ld pages_skipped %ld range_start %llu range_end %llu nonblocking %d for_kupdate %d for_reclaim %d range_cyclic %d writeback_index %lu",
-		  jbd2_dev_to_name(__entry->dev),
+	TP_printk("dev %d,%d ino %lu nr_to_write %ld pages_skipped %ld range_start %llu range_end %llu nonblocking %d for_kupdate %d for_reclaim %d range_cyclic %d writeback_index %lu",
+		  __entry->dev_major, __entry->dev_minor,
 		  (unsigned long) __entry->ino, __entry->nr_to_write,
 		  __entry->pages_skipped, __entry->range_start,
 		  __entry->range_end, __entry->nonblocking,
@@ -265,7 +283,8 @@ TRACE_EVENT(ext4_da_write_pages,
 	TP_ARGS(inode, mpd),
 
 	TP_STRUCT__entry(
-		__field(	dev_t,	dev			)
+		__field(	int,   dev_major                )
+		__field(	int,   dev_minor                )
 		__field(	ino_t,	ino			)
 		__field(	__u64,	b_blocknr		)
 		__field(	__u32,	b_size			)
@@ -276,7 +295,8 @@ TRACE_EVENT(ext4_da_write_pages,
 	),
 
 	TP_fast_assign(
-		__entry->dev		= inode->i_sb->s_dev;
+		__entry->dev_major	= MAJOR(inode->i_sb->s_dev);
+		__entry->dev_minor	= MINOR(inode->i_sb->s_dev);
 		__entry->ino		= inode->i_ino;
 		__entry->b_blocknr	= mpd->b_blocknr;
 		__entry->b_size		= mpd->b_size;
@@ -286,8 +306,9 @@ TRACE_EVENT(ext4_da_write_pages,
 		__entry->pages_written	= mpd->pages_written;
 	),
 
-	TP_printk("dev %s ino %lu b_blocknr %llu b_size %u b_state 0x%04x first_page %lu io_done %d pages_written %d",
-		  jbd2_dev_to_name(__entry->dev), (unsigned long) __entry->ino,
+	TP_printk("dev %d,%d ino %lu b_blocknr %llu b_size %u b_state 0x%04x first_page %lu io_done %d pages_written %d",
+		  __entry->dev_major, __entry->dev_minor,
+		  (unsigned long) __entry->ino,
 		  __entry->b_blocknr, __entry->b_size,
 		  __entry->b_state, __entry->first_page,
 		  __entry->io_done, __entry->pages_written)
@@ -300,7 +321,8 @@ TRACE_EVENT(ext4_da_writepages_result,
 	TP_ARGS(inode, wbc, ret, pages_written),
 
 	TP_STRUCT__entry(
-		__field(	dev_t,	dev			)
+		__field(	int,   dev_major                )
+		__field(	int,   dev_minor                )
 		__field(	ino_t,	ino			)
 		__field(	int,	ret			)
 		__field(	int,	pages_written		)
@@ -310,7 +332,8 @@ TRACE_EVENT(ext4_da_writepages_result,
 	),
 
 	TP_fast_assign(
-		__entry->dev		= inode->i_sb->s_dev;
+		__entry->dev_major	= MAJOR(inode->i_sb->s_dev);
+		__entry->dev_minor	= MINOR(inode->i_sb->s_dev);
 		__entry->ino		= inode->i_ino;
 		__entry->ret		= ret;
 		__entry->pages_written	= pages_written;
@@ -319,8 +342,8 @@ TRACE_EVENT(ext4_da_writepages_result,
 		__entry->writeback_index = inode->i_mapping->writeback_index;
 	),
 
-	TP_printk("dev %s ino %lu ret %d pages_written %d pages_skipped %ld more_io %d writeback_index %lu",
-		  jbd2_dev_to_name(__entry->dev),
+	TP_printk("dev %d,%d ino %lu ret %d pages_written %d pages_skipped %ld more_io %d writeback_index %lu",
+		  __entry->dev_major, __entry->dev_minor,
 		  (unsigned long) __entry->ino, __entry->ret,
 		  __entry->pages_written, __entry->pages_skipped,
 		  __entry->more_io,
@@ -334,20 +357,23 @@ TRACE_EVENT(ext4_discard_blocks,
 	TP_ARGS(sb, blk, count),
 
 	TP_STRUCT__entry(
-		__field(	dev_t,	dev			)
+		__field(	int,   dev_major                )
+		__field(	int,   dev_minor                )
 		__field(	__u64,	blk			)
 		__field(	__u64,	count			)
 
 	),
 
 	TP_fast_assign(
-		__entry->dev	= sb->s_dev;
+		__entry->dev_major = MAJOR(sb->s_dev);
+		__entry->dev_minor = MINOR(sb->s_dev);
 		__entry->blk	= blk;
 		__entry->count	= count;
 	),
 
-	TP_printk("dev %s blk %llu count %llu",
-		  jbd2_dev_to_name(__entry->dev), __entry->blk, __entry->count)
+	TP_printk("dev %d,%d blk %llu count %llu",
+		  __entry->dev_major, __entry->dev_minor,
+		  __entry->blk, __entry->count)
 );
 
 DECLARE_EVENT_CLASS(ext4__mb_new_pa,
@@ -357,7 +383,8 @@ DECLARE_EVENT_CLASS(ext4__mb_new_pa,
 	TP_ARGS(ac, pa),
 
 	TP_STRUCT__entry(
-		__field(	dev_t,	dev			)
+		__field(	int,   dev_major                )
+		__field(	int,   dev_minor                )
 		__field(	ino_t,	ino			)
 		__field(	__u64,	pa_pstart		)
 		__field(	__u32,	pa_len			)
@@ -366,16 +393,18 @@ DECLARE_EVENT_CLASS(ext4__mb_new_pa,
 	),
 
 	TP_fast_assign(
-		__entry->dev		= ac->ac_sb->s_dev;
+		__entry->dev_major	= MAJOR(ac->ac_sb->s_dev);
+		__entry->dev_minor	= MINOR(ac->ac_sb->s_dev);
 		__entry->ino		= ac->ac_inode->i_ino;
 		__entry->pa_pstart	= pa->pa_pstart;
 		__entry->pa_len		= pa->pa_len;
 		__entry->pa_lstart	= pa->pa_lstart;
 	),
 
-	TP_printk("dev %s ino %lu pstart %llu len %u lstart %llu",
-		  jbd2_dev_to_name(__entry->dev), (unsigned long) __entry->ino,
-		  __entry->pa_pstart, __entry->pa_len, __entry->pa_lstart)
+	TP_printk("dev %d,%d ino %lu pstart %llu len %u lstart %llu",
+		  __entry->dev_major, __entry->dev_minor,
+		  (unsigned long) __entry->ino, __entry->pa_pstart,
+		  __entry->pa_len, __entry->pa_lstart)
 );
 
 DEFINE_EVENT(ext4__mb_new_pa, ext4_mb_new_inode_pa,
@@ -403,7 +432,8 @@ TRACE_EVENT(ext4_mb_release_inode_pa,
 	TP_ARGS(sb, inode, pa, block, count),
 
 	TP_STRUCT__entry(
-		__field(	dev_t,	dev			)
+		__field(	int,   dev_major                )
+		__field(	int,   dev_minor                )
 		__field(	ino_t,	ino			)
 		__field(	__u64,	block			)
 		__field(	__u32,	count			)
@@ -411,15 +441,16 @@ TRACE_EVENT(ext4_mb_release_inode_pa,
 	),
 
 	TP_fast_assign(
-		__entry->dev		= sb->s_dev;
+		__entry->dev_major	= MAJOR(sb->s_dev);
+		__entry->dev_minor	= MINOR(sb->s_dev);
 		__entry->ino		= inode->i_ino;
 		__entry->block		= block;
 		__entry->count		= count;
 	),
 
-	TP_printk("dev %s ino %lu block %llu count %u",
-		  jbd2_dev_to_name(__entry->dev), (unsigned long) __entry->ino,
-		  __entry->block, __entry->count)
+	TP_printk("dev %d,%d ino %lu block %llu count %u",
+		  __entry->dev_major, __entry->dev_minor,
+		  (unsigned long) __entry->ino, __entry->block, __entry->count)
 );
 
 TRACE_EVENT(ext4_mb_release_group_pa,
@@ -429,20 +460,23 @@ TRACE_EVENT(ext4_mb_release_group_pa,
 	TP_ARGS(sb, pa),
 
 	TP_STRUCT__entry(
-		__field(	dev_t,	dev			)
+		__field(	int,   dev_major                )
+		__field(	int,   dev_minor                )
 		__field(	__u64,	pa_pstart		)
 		__field(	__u32,	pa_len			)
 
 	),
 
 	TP_fast_assign(
-		__entry->dev		= sb->s_dev;
+		__entry->dev_major	= MAJOR(sb->s_dev);
+		__entry->dev_minor	= MINOR(sb->s_dev);
 		__entry->pa_pstart	= pa->pa_pstart;
 		__entry->pa_len		= pa->pa_len;
 	),
 
-	TP_printk("dev %s pstart %llu len %u",
-		  jbd2_dev_to_name(__entry->dev), __entry->pa_pstart, __entry->pa_len)
+	TP_printk("dev %d,%d pstart %llu len %u",
+		  __entry->dev_major, __entry->dev_minor,
+		  __entry->pa_pstart, __entry->pa_len)
 );
 
 TRACE_EVENT(ext4_discard_preallocations,
@@ -451,18 +485,21 @@ TRACE_EVENT(ext4_discard_preallocations,
 	TP_ARGS(inode),
 
 	TP_STRUCT__entry(
-		__field(	dev_t,	dev			)
+		__field(	int,   dev_major                )
+		__field(	int,   dev_minor                )
 		__field(	ino_t,	ino			)
 
 	),
 
 	TP_fast_assign(
-		__entry->dev	= inode->i_sb->s_dev;
+		__entry->dev_major = MAJOR(inode->i_sb->s_dev);
+		__entry->dev_minor = MINOR(inode->i_sb->s_dev);
 		__entry->ino	= inode->i_ino;
 	),
 
-	TP_printk("dev %s ino %lu",
-		  jbd2_dev_to_name(__entry->dev), (unsigned long) __entry->ino)
+	TP_printk("dev %d,%d ino %lu",
+		  __entry->dev_major, __entry->dev_minor,
+		  (unsigned long) __entry->ino)
 );
 
 TRACE_EVENT(ext4_mb_discard_preallocations,
@@ -471,18 +508,20 @@ TRACE_EVENT(ext4_mb_discard_preallocations,
 	TP_ARGS(sb, needed),
 
 	TP_STRUCT__entry(
-		__field(	dev_t,	dev			)
+		__field(	int,   dev_major                )
+		__field(	int,   dev_minor                )
 		__field(	int,	needed			)
 
 	),
 
 	TP_fast_assign(
-		__entry->dev	= sb->s_dev;
+		__entry->dev_major = MAJOR(sb->s_dev);
+		__entry->dev_minor = MINOR(sb->s_dev);
 		__entry->needed	= needed;
 	),
 
-	TP_printk("dev %s needed %d",
-		  jbd2_dev_to_name(__entry->dev), __entry->needed)
+	TP_printk("dev %d,%d needed %d",
+		  __entry->dev_major, __entry->dev_minor, __entry->needed)
 );
 
 TRACE_EVENT(ext4_request_blocks,
@@ -491,7 +530,8 @@ TRACE_EVENT(ext4_request_blocks,
 	TP_ARGS(ar),
 
 	TP_STRUCT__entry(
-		__field(	dev_t,	dev			)
+		__field(	int,   dev_major                )
+		__field(	int,   dev_minor                )
 		__field(	ino_t,	ino			)
 		__field(	unsigned int, flags		)
 		__field(	unsigned int, len		)
@@ -504,7 +544,8 @@ TRACE_EVENT(ext4_request_blocks,
 	),
 
 	TP_fast_assign(
-		__entry->dev	= ar->inode->i_sb->s_dev;
+		__entry->dev_major = MAJOR(ar->inode->i_sb->s_dev);
+		__entry->dev_minor = MINOR(ar->inode->i_sb->s_dev);
 		__entry->ino	= ar->inode->i_ino;
 		__entry->flags	= ar->flags;
 		__entry->len	= ar->len;
@@ -516,8 +557,9 @@ TRACE_EVENT(ext4_request_blocks,
 		__entry->pright	= ar->pright;
 	),
 
-	TP_printk("dev %s ino %lu flags %u len %u lblk %llu goal %llu lleft %llu lright %llu pleft %llu pright %llu ",
-		  jbd2_dev_to_name(__entry->dev), (unsigned long) __entry->ino,
+	TP_printk("dev %d,%d ino %lu flags %u len %u lblk %llu goal %llu lleft %llu lright %llu pleft %llu pright %llu ",
+		  __entry->dev_major, __entry->dev_minor,
+		  (unsigned long) __entry->ino,
 		  __entry->flags, __entry->len,
 		  (unsigned long long) __entry->logical,
 		  (unsigned long long) __entry->goal,
@@ -533,7 +575,8 @@ TRACE_EVENT(ext4_allocate_blocks,
 	TP_ARGS(ar, block),
 
 	TP_STRUCT__entry(
-		__field(	dev_t,	dev			)
+		__field(	int,   dev_major                )
+		__field(	int,   dev_minor                )
 		__field(	ino_t,	ino			)
 		__field(	__u64,	block			)
 		__field(	unsigned int, flags		)
@@ -547,7 +590,8 @@ TRACE_EVENT(ext4_allocate_blocks,
 	),
 
 	TP_fast_assign(
-		__entry->dev	= ar->inode->i_sb->s_dev;
+		__entry->dev_major = MAJOR(ar->inode->i_sb->s_dev);
+		__entry->dev_minor = MINOR(ar->inode->i_sb->s_dev);
 		__entry->ino	= ar->inode->i_ino;
 		__entry->block	= block;
 		__entry->flags	= ar->flags;
@@ -560,9 +604,10 @@ TRACE_EVENT(ext4_allocate_blocks,
 		__entry->pright	= ar->pright;
 	),
 
-	TP_printk("dev %s ino %lu flags %u len %u block %llu lblk %llu goal %llu lleft %llu lright %llu pleft %llu pright %llu ",
-		  jbd2_dev_to_name(__entry->dev), (unsigned long) __entry->ino,
-		  __entry->flags, __entry->len, __entry->block,
+	TP_printk("dev %d,%d ino %lu flags %u len %u block %llu lblk %llu goal %llu lleft %llu lright %llu pleft %llu pright %llu ",
+		  __entry->dev_major, __entry->dev_minor,
+		  (unsigned long) __entry->ino, __entry->flags,
+		  __entry->len, __entry->block,
 		  (unsigned long long) __entry->logical,
 		  (unsigned long long) __entry->goal,
 		  (unsigned long long) __entry->lleft,
@@ -578,7 +623,8 @@ TRACE_EVENT(ext4_free_blocks,
 	TP_ARGS(inode, block, count, flags),
 
 	TP_STRUCT__entry(
-		__field(	dev_t,	dev			)
+		__field(	int,   dev_major                )
+		__field(	int,   dev_minor                )
 		__field(	ino_t,	ino			)
 		__field(      umode_t, mode			)
 		__field(	__u64,	block			)
@@ -587,7 +633,8 @@ TRACE_EVENT(ext4_free_blocks,
 	),
 
 	TP_fast_assign(
-		__entry->dev		= inode->i_sb->s_dev;
+		__entry->dev_major	= MAJOR(inode->i_sb->s_dev);
+		__entry->dev_minor	= MINOR(inode->i_sb->s_dev);
 		__entry->ino		= inode->i_ino;
 		__entry->mode		= inode->i_mode;
 		__entry->block		= block;
@@ -595,8 +642,9 @@ TRACE_EVENT(ext4_free_blocks,
 		__entry->flags		= flags;
 	),
 
-	TP_printk("dev %s ino %lu mode 0%o block %llu count %lu flags %d",
-		  jbd2_dev_to_name(__entry->dev), (unsigned long) __entry->ino,
+	TP_printk("dev %d,%d ino %lu mode 0%o block %llu count %lu flags %d",
+		  __entry->dev_major, __entry->dev_minor,
+		  (unsigned long) __entry->ino,
 		  __entry->mode, __entry->block, __entry->count,
 		  __entry->flags)
 );
@@ -607,7 +655,8 @@ TRACE_EVENT(ext4_sync_file,
 	TP_ARGS(file, datasync),
 
 	TP_STRUCT__entry(
-		__field(	dev_t,	dev			)
+		__field(	int,   dev_major                )
+		__field(	int,   dev_minor                )
 		__field(	ino_t,	ino			)
 		__field(	ino_t,	parent			)
 		__field(	int,	datasync		)
@@ -616,14 +665,16 @@ TRACE_EVENT(ext4_sync_file,
 	TP_fast_assign(
 		struct dentry *dentry = file->f_path.dentry;
 
-		__entry->dev		= dentry->d_inode->i_sb->s_dev;
+		__entry->dev_major	= MAJOR(dentry->d_inode->i_sb->s_dev);
+		__entry->dev_minor	= MINOR(dentry->d_inode->i_sb->s_dev);
 		__entry->ino		= dentry->d_inode->i_ino;
 		__entry->datasync	= datasync;
 		__entry->parent		= dentry->d_parent->d_inode->i_ino;
 	),
 
-	TP_printk("dev %s ino %ld parent %ld datasync %d ",
-		  jbd2_dev_to_name(__entry->dev), (unsigned long) __entry->ino,
+	TP_printk("dev %d,%d ino %ld parent %ld datasync %d ",
+		  __entry->dev_major, __entry->dev_minor,
+		  (unsigned long) __entry->ino,
 		  (unsigned long) __entry->parent, __entry->datasync)
 );
 
@@ -633,18 +684,20 @@ TRACE_EVENT(ext4_sync_fs,
 	TP_ARGS(sb, wait),
 
 	TP_STRUCT__entry(
-		__field(	dev_t,	dev			)
+		__field(	int,   dev_major                )
+		__field(	int,   dev_minor                )
 		__field(	int,	wait			)
 
 	),
 
 	TP_fast_assign(
-		__entry->dev	= sb->s_dev;
+		__entry->dev_major = MAJOR(sb->s_dev);
+		__entry->dev_minor = MINOR(sb->s_dev);
 		__entry->wait	= wait;
 	),
 
-	TP_printk("dev %s wait %d", jbd2_dev_to_name(__entry->dev),
-		  __entry->wait)
+	TP_printk("dev %d,%d wait %d", __entry->dev_major,
+		  __entry->dev_minor, __entry->wait)
 );
 
 TRACE_EVENT(ext4_alloc_da_blocks,
@@ -653,21 +706,24 @@ TRACE_EVENT(ext4_alloc_da_blocks,
 	TP_ARGS(inode),
 
 	TP_STRUCT__entry(
-		__field(	dev_t,	dev			)
+		__field(	int,   dev_major                )
+		__field(	int,   dev_minor                )
 		__field(	ino_t,	ino			)
 		__field( unsigned int,	data_blocks	)
 		__field( unsigned int,	meta_blocks	)
 	),
 
 	TP_fast_assign(
-		__entry->dev	= inode->i_sb->s_dev;
+		__entry->dev_major = MAJOR(inode->i_sb->s_dev);
+		__entry->dev_minor = MINOR(inode->i_sb->s_dev);
 		__entry->ino	= inode->i_ino;
 		__entry->data_blocks = EXT4_I(inode)->i_reserved_data_blocks;
 		__entry->meta_blocks = EXT4_I(inode)->i_reserved_meta_blocks;
 	),
 
-	TP_printk("dev %s ino %lu data_blocks %u meta_blocks %u",
-		  jbd2_dev_to_name(__entry->dev), (unsigned long) __entry->ino,
+	TP_printk("dev %d,%d ino %lu data_blocks %u meta_blocks %u",
+		  __entry->dev_major, __entry->dev_minor,
+		  (unsigned long) __entry->ino,
 		  __entry->data_blocks, __entry->meta_blocks)
 );
 
@@ -677,7 +733,8 @@ TRACE_EVENT(ext4_mballoc_alloc,
 	TP_ARGS(ac),
 
 	TP_STRUCT__entry(
-		__field(	dev_t,	dev			)
+		__field(	int,   dev_major                )
+		__field(	int,   dev_minor                )
 		__field(	ino_t,	ino			)
 		__field(	__u16,	found			)
 		__field(	__u16,	groups			)
@@ -700,7 +757,8 @@ TRACE_EVENT(ext4_mballoc_alloc,
 	),
 
 	TP_fast_assign(
-		__entry->dev		= ac->ac_inode->i_sb->s_dev;
+		__entry->dev_major	= MAJOR(ac->ac_inode->i_sb->s_dev);
+		__entry->dev_minor	= MINOR(ac->ac_inode->i_sb->s_dev);
 		__entry->ino		= ac->ac_inode->i_ino;
 		__entry->found		= ac->ac_found;
 		__entry->flags		= ac->ac_flags;
@@ -722,10 +780,11 @@ TRACE_EVENT(ext4_mballoc_alloc,
 		__entry->result_len	= ac->ac_f_ex.fe_len;
 	),
 
-	TP_printk("dev %s inode %lu orig %u/%d/%u@%u goal %u/%d/%u@%u "
+	TP_printk("dev %d,%d inode %lu orig %u/%d/%u@%u goal %u/%d/%u@%u "
 		  "result %u/%d/%u@%u blks %u grps %u cr %u flags 0x%04x "
 		  "tail %u broken %u",
-		  jbd2_dev_to_name(__entry->dev), (unsigned long) __entry->ino,
+		  __entry->dev_major, __entry->dev_minor,
+		  (unsigned long) __entry->ino,
 		  __entry->orig_group, __entry->orig_start,
 		  __entry->orig_len, __entry->orig_logical,
 		  __entry->goal_group, __entry->goal_start,
@@ -743,7 +802,8 @@ TRACE_EVENT(ext4_mballoc_prealloc,
 	TP_ARGS(ac),
 
 	TP_STRUCT__entry(
-		__field(	dev_t,	dev			)
+		__field(	int,   dev_major                )
+		__field(	int,   dev_minor                )
 		__field(	ino_t,	ino			)
 		__field(	__u32, 	orig_logical		)
 		__field(	  int,	orig_start		)
@@ -756,7 +816,8 @@ TRACE_EVENT(ext4_mballoc_prealloc,
 	),
 
 	TP_fast_assign(
-		__entry->dev		= ac->ac_inode->i_sb->s_dev;
+		__entry->dev_major	= MAJOR(ac->ac_inode->i_sb->s_dev);
+		__entry->dev_minor	= MINOR(ac->ac_inode->i_sb->s_dev);
 		__entry->ino		= ac->ac_inode->i_ino;
 		__entry->orig_logical	= ac->ac_o_ex.fe_logical;
 		__entry->orig_start	= ac->ac_o_ex.fe_start;
@@ -768,8 +829,9 @@ TRACE_EVENT(ext4_mballoc_prealloc,
 		__entry->result_len	= ac->ac_b_ex.fe_len;
 	),
 
-	TP_printk("dev %s inode %lu orig %u/%d/%u@%u result %u/%d/%u@%u",
-		  jbd2_dev_to_name(__entry->dev), (unsigned long) __entry->ino,
+	TP_printk("dev %d,%d inode %lu orig %u/%d/%u@%u result %u/%d/%u@%u",
+		  __entry->dev_major, __entry->dev_minor,
+		  (unsigned long) __entry->ino,
 		  __entry->orig_group, __entry->orig_start,
 		  __entry->orig_len, __entry->orig_logical,
 		  __entry->result_group, __entry->result_start,
@@ -786,7 +848,8 @@ DECLARE_EVENT_CLASS(ext4__mballoc,
 	TP_ARGS(sb, inode, group, start, len),
 
 	TP_STRUCT__entry(
-		__field(	dev_t,	dev			)
+		__field(	int,   dev_major                )
+		__field(	int,   dev_minor                )
 		__field(	ino_t,	ino			)
 		__field(	  int,	result_start		)
 		__field(	__u32, 	result_group		)
@@ -794,15 +857,17 @@ DECLARE_EVENT_CLASS(ext4__mballoc,
 	),
 
 	TP_fast_assign(
-		__entry->dev		= sb->s_dev;
+		__entry->dev_major	= MAJOR(sb->s_dev);
+		__entry->dev_minor	= MINOR(sb->s_dev);
 		__entry->ino		= inode ? inode->i_ino : 0;
 		__entry->result_start	= start;
 		__entry->result_group	= group;
 		__entry->result_len	= len;
 	),
 
-	TP_printk("dev %s inode %lu extent %u/%d/%u ",
-		  jbd2_dev_to_name(__entry->dev), (unsigned long) __entry->ino,
+	TP_printk("dev %d,%d inode %lu extent %u/%d/%u ",
+		  __entry->dev_major, __entry->dev_minor,
+		  (unsigned long) __entry->ino,
 		  __entry->result_group, __entry->result_start,
 		  __entry->result_len)
 );
@@ -835,7 +900,8 @@ TRACE_EVENT(ext4_forget,
 	TP_ARGS(inode, is_metadata, block),
 
 	TP_STRUCT__entry(
-		__field(	dev_t,	dev			)
+		__field(	int,   dev_major                )
+		__field(	int,   dev_minor                )
 		__field(	ino_t,	ino			)
 		__field(	umode_t, mode			)
 		__field(	int,	is_metadata		)
@@ -843,16 +909,18 @@ TRACE_EVENT(ext4_forget,
 	),
 
 	TP_fast_assign(
-		__entry->dev	= inode->i_sb->s_dev;
+		__entry->dev_major = MAJOR(inode->i_sb->s_dev);
+		__entry->dev_minor = MINOR(inode->i_sb->s_dev);
 		__entry->ino	= inode->i_ino;
 		__entry->mode	= inode->i_mode;
 		__entry->is_metadata = is_metadata;
 		__entry->block	= block;
 	),
 
-	TP_printk("dev %s ino %lu mode 0%o is_metadata %d block %llu",
-		  jbd2_dev_to_name(__entry->dev), (unsigned long) __entry->ino,
-		  __entry->mode, __entry->is_metadata, __entry->block)
+	TP_printk("dev %d,%d ino %lu mode 0%o is_metadata %d block %llu",
+		  __entry->dev_major, __entry->dev_minor,
+		  (unsigned long) __entry->ino, __entry->mode,
+		  __entry->is_metadata, __entry->block)
 );
 
 TRACE_EVENT(ext4_da_update_reserve_space,
@@ -861,7 +929,8 @@ TRACE_EVENT(ext4_da_update_reserve_space,
 	TP_ARGS(inode, used_blocks),
 
 	TP_STRUCT__entry(
-		__field(	dev_t,	dev			)
+		__field(	int,   dev_major                )
+		__field(	int,   dev_minor                )
 		__field(	ino_t,	ino			)
 		__field(	umode_t, mode			)
 		__field(	__u64,	i_blocks		)
@@ -872,7 +941,8 @@ TRACE_EVENT(ext4_da_update_reserve_space,
 	),
 
 	TP_fast_assign(
-		__entry->dev	= inode->i_sb->s_dev;
+		__entry->dev_major = MAJOR(inode->i_sb->s_dev);
+		__entry->dev_minor = MINOR(inode->i_sb->s_dev);
 		__entry->ino	= inode->i_ino;
 		__entry->mode	= inode->i_mode;
 		__entry->i_blocks = inode->i_blocks;
@@ -882,9 +952,10 @@ TRACE_EVENT(ext4_da_update_reserve_space,
 		__entry->allocated_meta_blocks = EXT4_I(inode)->i_allocated_meta_blocks;
 	),
 
-	TP_printk("dev %s ino %lu mode 0%o i_blocks %llu used_blocks %d reserved_data_blocks %d reserved_meta_blocks %d allocated_meta_blocks %d",
-		  jbd2_dev_to_name(__entry->dev), (unsigned long) __entry->ino,
-		  __entry->mode,  (unsigned long long) __entry->i_blocks,
+	TP_printk("dev %d,%d ino %lu mode 0%o i_blocks %llu used_blocks %d reserved_data_blocks %d reserved_meta_blocks %d allocated_meta_blocks %d",
+		  __entry->dev_major, __entry->dev_minor,
+		  (unsigned long) __entry->ino, __entry->mode,
+		  (unsigned long long) __entry->i_blocks,
 		  __entry->used_blocks, __entry->reserved_data_blocks,
 		  __entry->reserved_meta_blocks, __entry->allocated_meta_blocks)
 );
@@ -895,7 +966,8 @@ TRACE_EVENT(ext4_da_reserve_space,
 	TP_ARGS(inode, md_needed),
 
 	TP_STRUCT__entry(
-		__field(	dev_t,	dev			)
+		__field(	int,   dev_major                )
+		__field(	int,   dev_minor                )
 		__field(	ino_t,	ino			)
 		__field(	umode_t, mode			)
 		__field(	__u64,	i_blocks		)
@@ -905,7 +977,8 @@ TRACE_EVENT(ext4_da_reserve_space,
 	),
 
 	TP_fast_assign(
-		__entry->dev	= inode->i_sb->s_dev;
+		__entry->dev_major = MAJOR(inode->i_sb->s_dev);
+		__entry->dev_minor = MINOR(inode->i_sb->s_dev);
 		__entry->ino	= inode->i_ino;
 		__entry->mode	= inode->i_mode;
 		__entry->i_blocks = inode->i_blocks;
@@ -914,8 +987,9 @@ TRACE_EVENT(ext4_da_reserve_space,
 		__entry->reserved_meta_blocks = EXT4_I(inode)->i_reserved_meta_blocks;
 	),
 
-	TP_printk("dev %s ino %lu mode 0%o i_blocks %llu md_needed %d reserved_data_blocks %d reserved_meta_blocks %d",
-		  jbd2_dev_to_name(__entry->dev), (unsigned long) __entry->ino,
+	TP_printk("dev %d,%d ino %lu mode 0%o i_blocks %llu md_needed %d reserved_data_blocks %d reserved_meta_blocks %d",
+		  __entry->dev_major, __entry->dev_minor,
+		  (unsigned long) __entry->ino,
 		  __entry->mode, (unsigned long long) __entry->i_blocks,
 		  __entry->md_needed, __entry->reserved_data_blocks,
 		  __entry->reserved_meta_blocks)
@@ -927,7 +1001,8 @@ TRACE_EVENT(ext4_da_release_space,
 	TP_ARGS(inode, freed_blocks),
 
 	TP_STRUCT__entry(
-		__field(	dev_t,	dev			)
+		__field(	int,   dev_major                )
+		__field(	int,   dev_minor                )
 		__field(	ino_t,	ino			)
 		__field(	umode_t, mode			)
 		__field(	__u64,	i_blocks		)
@@ -938,7 +1013,8 @@ TRACE_EVENT(ext4_da_release_space,
 	),
 
 	TP_fast_assign(
-		__entry->dev	= inode->i_sb->s_dev;
+		__entry->dev_major = MAJOR(inode->i_sb->s_dev);
+		__entry->dev_minor = MINOR(inode->i_sb->s_dev);
 		__entry->ino	= inode->i_ino;
 		__entry->mode	= inode->i_mode;
 		__entry->i_blocks = inode->i_blocks;
@@ -948,8 +1024,9 @@ TRACE_EVENT(ext4_da_release_space,
 		__entry->allocated_meta_blocks = EXT4_I(inode)->i_allocated_meta_blocks;
 	),
 
-	TP_printk("dev %s ino %lu mode 0%o i_blocks %llu freed_blocks %d reserved_data_blocks %d reserved_meta_blocks %d allocated_meta_blocks %d",
-		  jbd2_dev_to_name(__entry->dev), (unsigned long) __entry->ino,
+	TP_printk("dev %d,%d ino %lu mode 0%o i_blocks %llu freed_blocks %d reserved_data_blocks %d reserved_meta_blocks %d allocated_meta_blocks %d",
+		  __entry->dev_major, __entry->dev_minor,
+		  (unsigned long) __entry->ino,
 		  __entry->mode, (unsigned long long) __entry->i_blocks,
 		  __entry->freed_blocks, __entry->reserved_data_blocks,
 		  __entry->reserved_meta_blocks, __entry->allocated_meta_blocks)
@@ -961,18 +1038,20 @@ DECLARE_EVENT_CLASS(ext4__bitmap_load,
 	TP_ARGS(sb, group),
 
 	TP_STRUCT__entry(
-		__field(	dev_t,	dev			)
+		__field(	int,   dev_major                )
+		__field(	int,   dev_minor                )
 		__field(	__u32,	group			)
 
 	),
 
 	TP_fast_assign(
-		__entry->dev	= sb->s_dev;
+		__entry->dev_major = MAJOR(sb->s_dev);
+		__entry->dev_minor = MINOR(sb->s_dev);
 		__entry->group	= group;
 	),
 
-	TP_printk("dev %s group %u",
-		  jbd2_dev_to_name(__entry->dev), __entry->group)
+	TP_printk("dev %d,%d group %u",
+		  __entry->dev_major, __entry->dev_minor, __entry->group)
 );
 
 DEFINE_EVENT(ext4__bitmap_load, ext4_mb_bitmap_load,
diff --git a/include/trace/events/jbd2.h b/include/trace/events/jbd2.h
index bf16545..7447ea9 100644
--- a/include/trace/events/jbd2.h
+++ b/include/trace/events/jbd2.h
@@ -17,17 +17,19 @@ TRACE_EVENT(jbd2_checkpoint,
 	TP_ARGS(journal, result),
 
 	TP_STRUCT__entry(
-		__field(	dev_t,	dev			)
+		__field(	int,	dev_major		)
+		__field(	int,	dev_minor		)
 		__field(	int,	result			)
 	),
 
 	TP_fast_assign(
-		__entry->dev		= journal->j_fs_dev->bd_dev;
+		__entry->dev_major	= MAJOR(journal->j_fs_dev->bd_dev);
+		__entry->dev_minor	= MINOR(journal->j_fs_dev->bd_dev);
 		__entry->result		= result;
 	),
 
-	TP_printk("dev %s result %d",
-		  jbd2_dev_to_name(__entry->dev), __entry->result)
+	TP_printk("dev %d,%d result %d",
+		  __entry->dev_major, __entry->dev_minor, __entry->result)
 );
 
 DECLARE_EVENT_CLASS(jbd2_commit,
@@ -37,20 +39,22 @@ DECLARE_EVENT_CLASS(jbd2_commit,
 	TP_ARGS(journal, commit_transaction),
 
 	TP_STRUCT__entry(
-		__field(	dev_t,	dev			)
+		__field(	int,   dev_major                )
+		__field(	int,   dev_minor                )
 		__field(	char,	sync_commit		  )
 		__field(	int,	transaction		  )
 	),
 
 	TP_fast_assign(
-		__entry->dev		= journal->j_fs_dev->bd_dev;
+		__entry->dev_major	= MAJOR(journal->j_fs_dev->bd_dev);
+		__entry->dev_minor	= MINOR(journal->j_fs_dev->bd_dev);
 		__entry->sync_commit = commit_transaction->t_synchronous_commit;
 		__entry->transaction	= commit_transaction->t_tid;
 	),
 
-	TP_printk("dev %s transaction %d sync %d",
-		  jbd2_dev_to_name(__entry->dev), __entry->transaction,
-		  __entry->sync_commit)
+	TP_printk("dev %d,%d transaction %d sync %d",
+		  __entry->dev_major, __entry->dev_minor,
+		  __entry->transaction, __entry->sync_commit)
 );
 
 DEFINE_EVENT(jbd2_commit, jbd2_start_commit,
@@ -87,22 +91,24 @@ TRACE_EVENT(jbd2_end_commit,
 	TP_ARGS(journal, commit_transaction),
 
 	TP_STRUCT__entry(
-		__field(	dev_t,	dev			)
+		__field(	int,   dev_major                )
+		__field(	int,   dev_minor                )
 		__field(	char,	sync_commit		  )
 		__field(	int,	transaction		  )
 		__field(	int,	head		  	  )
 	),
 
 	TP_fast_assign(
-		__entry->dev		= journal->j_fs_dev->bd_dev;
+		__entry->dev_major	= MAJOR(journal->j_fs_dev->bd_dev);
+		__entry->dev_minor	= MINOR(journal->j_fs_dev->bd_dev);
 		__entry->sync_commit = commit_transaction->t_synchronous_commit;
 		__entry->transaction	= commit_transaction->t_tid;
 		__entry->head		= journal->j_tail_sequence;
 	),
 
-	TP_printk("dev %s transaction %d sync %d head %d",
-		  jbd2_dev_to_name(__entry->dev), __entry->transaction,
-		  __entry->sync_commit, __entry->head)
+	TP_printk("dev %d,%d transaction %d sync %d head %d",
+		  __entry->dev_major, __entry->dev_minor,
+		  __entry->transaction, __entry->sync_commit, __entry->head)
 );
 
 TRACE_EVENT(jbd2_submit_inode_data,
@@ -111,17 +117,20 @@ TRACE_EVENT(jbd2_submit_inode_data,
 	TP_ARGS(inode),
 
 	TP_STRUCT__entry(
-		__field(	dev_t,	dev			)
+		__field(	int,   dev_major                )
+		__field(	int,   dev_minor                )
 		__field(	ino_t,	ino			)
 	),
 
 	TP_fast_assign(
-		__entry->dev	= inode->i_sb->s_dev;
+		__entry->dev_major = MAJOR(inode->i_sb->s_dev);
+		__entry->dev_minor = MINOR(inode->i_sb->s_dev);
 		__entry->ino	= inode->i_ino;
 	),
 
-	TP_printk("dev %s ino %lu",
-		  jbd2_dev_to_name(__entry->dev), (unsigned long) __entry->ino)
+	TP_printk("dev %d,%d ino %lu",
+		  __entry->dev_major, __entry->dev_minor,
+		  (unsigned long) __entry->ino)
 );
 
 TRACE_EVENT(jbd2_run_stats,
@@ -131,7 +140,8 @@ TRACE_EVENT(jbd2_run_stats,
 	TP_ARGS(dev, tid, stats),
 
 	TP_STRUCT__entry(
-		__field(		dev_t,	dev		)
+		__field(		  int,	dev_major	)
+		__field(		  int,	dev_minor	)
 		__field(	unsigned long,	tid		)
 		__field(	unsigned long,	wait		)
 		__field(	unsigned long,	running		)
@@ -144,7 +154,8 @@ TRACE_EVENT(jbd2_run_stats,
 	),
 
 	TP_fast_assign(
-		__entry->dev		= dev;
+		__entry->dev_major	= MAJOR(dev);
+		__entry->dev_minor	= MINOR(dev);
 		__entry->tid		= tid;
 		__entry->wait		= stats->rs_wait;
 		__entry->running	= stats->rs_running;
@@ -156,9 +167,9 @@ TRACE_EVENT(jbd2_run_stats,
 		__entry->blocks_logged	= stats->rs_blocks_logged;
 	),
 
-	TP_printk("dev %s tid %lu wait %u running %u locked %u flushing %u "
+	TP_printk("dev %d,%d tid %lu wait %u running %u locked %u flushing %u "
 		  "logging %u handle_count %u blocks %u blocks_logged %u",
-		  jbd2_dev_to_name(__entry->dev), __entry->tid,
+		  __entry->dev_major, __entry->dev_minor, __entry->tid,
 		  jiffies_to_msecs(__entry->wait),
 		  jiffies_to_msecs(__entry->running),
 		  jiffies_to_msecs(__entry->locked),
@@ -175,7 +186,8 @@ TRACE_EVENT(jbd2_checkpoint_stats,
 	TP_ARGS(dev, tid, stats),
 
 	TP_STRUCT__entry(
-		__field(		dev_t,	dev		)
+		__field(		  int,	dev_major	)
+		__field(		  int,	dev_minor	)
 		__field(	unsigned long,	tid		)
 		__field(	unsigned long,	chp_time	)
 		__field(		__u32,	forced_to_close	)
@@ -184,7 +196,8 @@ TRACE_EVENT(jbd2_checkpoint_stats,
 	),
 
 	TP_fast_assign(
-		__entry->dev		= dev;
+		__entry->dev_major	= MAJOR(dev);
+		__entry->dev_minor	= MINOR(dev);
 		__entry->tid		= tid;
 		__entry->chp_time	= stats->cs_chp_time;
 		__entry->forced_to_close= stats->cs_forced_to_close;
@@ -192,9 +205,9 @@ TRACE_EVENT(jbd2_checkpoint_stats,
 		__entry->dropped	= stats->cs_dropped;
 	),
 
-	TP_printk("dev %s tid %lu chp_time %u forced_to_close %u "
+	TP_printk("dev %d,%d tid %lu chp_time %u forced_to_close %u "
 		  "written %u dropped %u",
-		  jbd2_dev_to_name(__entry->dev), __entry->tid,
+		  __entry->dev_major, __entry->dev_minor, __entry->tid,
 		  jiffies_to_msecs(__entry->chp_time),
 		  __entry->forced_to_close, __entry->written, __entry->dropped)
 );
@@ -207,7 +220,8 @@ TRACE_EVENT(jbd2_cleanup_journal_tail,
 	TP_ARGS(journal, first_tid, block_nr, freed),
 
 	TP_STRUCT__entry(
-		__field(	dev_t,	dev			)
+		__field(	int,   dev_major                )
+		__field(	int,   dev_minor                )
 		__field(	tid_t,	tail_sequence		)
 		__field(	tid_t,	first_tid		)
 		__field(unsigned long,	block_nr		)
@@ -215,16 +229,18 @@ TRACE_EVENT(jbd2_cleanup_journal_tail,
 	),
 
 	TP_fast_assign(
-		__entry->dev		= journal->j_fs_dev->bd_dev;
+		__entry->dev_major	= MAJOR(journal->j_fs_dev->bd_dev);
+		__entry->dev_minor	= MINOR(journal->j_fs_dev->bd_dev);
 		__entry->tail_sequence	= journal->j_tail_sequence;
 		__entry->first_tid	= first_tid;
 		__entry->block_nr	= block_nr;
 		__entry->freed		= freed;
 	),
 
-	TP_printk("dev %s from %u to %u offset %lu freed %lu",
-		  jbd2_dev_to_name(__entry->dev), __entry->tail_sequence,
-		  __entry->first_tid, __entry->block_nr, __entry->freed)
+	TP_printk("dev %d,%d from %u to %u offset %lu freed %lu",
+		  __entry->dev_major, __entry->dev_minor,
+		  __entry->tail_sequence, __entry->first_tid,
+		  __entry->block_nr, __entry->freed)
 );
 
 #endif /* _TRACE_JBD2_H */

Re: Perf can't deal with many tracepoints

[David Daney]

On 10/27/2010 04:20 PM, Theodore Ts'o wrote:
> Perf will drop dead if it comes across tracepoints that have anything
> but primitive structure accessors in the TP_printk() section of the
> tracepoint definition.  For example, the ext4 and jbd2 tracepoints uses
> jbd2_dev_to_name() to translate a dev_t to a string.  The block I/O
> tracepoints uses MAJOR() and MINOR() to translate a dev_t to a
> major/minor number pair.  Both do this in TP_printk.  This results in a
> fatal error:
>
> # perf record -R -c 1 -e ext4:ext4_da_writepages sh -c "cp -r /boot /test; sync"
> [ perf record: Woken up 1 times to write data ]
> [ perf record: Captured and wrote 0.110 MB perf.data (~4786 samples) ]
> # perf trace -i perf.data
>    Fatal: no argument match
>                cp-9792   [007] 1181919.509759: ext4_da_writepages: dev jbd2_dev_to_name ino
>
> There are people roaming around trying to convince me that perf is the
> One True Way to do everything, including tracepoints.  But there are a
> whole bunch of tracepoints that perf can't handle.  It seems to me we
> have three possible solutions:
>
> 1) Accept there are some tracepoints perf just can't handle, and just
> say that ftrace is the only way people can use those tracepoints
>
> 2) Enforce a rule which says that nothing other than primitive structure
> accessors are allowed, in which case we need a patch such like the one
> attached.  (We will need to audit all tracepoints; it's more than just
> ext4, as I've mentioned --- and yes, the patch below is ugly.  But it
> may be what I have to do to accomodate perf --- or maybe I should just
> tell people that perf is not supported, and if you want to use ext4 or
> block I/O tracepoints, you should use ftrace?)
>
> 3) Figure out some way of making perf smarter; I don't know how to do
> that in the general case, since it can't handle arbitrary C statements.
> But maybe it could be taught how to handle dev_t's in some intelligent
> fashion, perhaps.  And then combine this with either (1) or (2) above.
>
> What say ye?
>

Tracing is supposed to be low overhead.  Forcing people to decode things 
like this at the trace point, may take more code and cause the trace 
data to be larger, making it slower than necessary.

If there isn't a good reason to keep perf stupid, then making it smarter 
could be attractive.

That said, there is some tracepoint data that even Steve's offline 
ftrace analysis tools cannot handle on some architectures.  PFN comes to 
mind on Sparse Mem MIPS systems.  So the argument that only primitive 
structure accessors be allowed has some merits as well.

David Daney

Re: Perf can't deal with many tracepoints

[Ted Ts'o]

On Wed, Oct 27, 2010 at 05:16:18PM -0700, David Daney wrote:
> Tracing is supposed to be low overhead.  Forcing people to decode
> things like this at the trace point, may take more code and cause
> the trace data to be larger, making it slower than necessary.
> 
> If there isn't a good reason to keep perf stupid, then making it
> smarter could be attractive.

Agreed.  Although one argument against making perf smarter is that
certain things such as the dev_t MAJOR/MINOR split is an internal
abstraction that could potentially vary from kernel to kernel.

And the question is whether perf really should be so different that if
you boot a different kernel, you had better have the right perf
installed.

							- Ted

Re: Perf can't deal with many tracepoints

[David Daney]

On 10/27/2010 05:40 PM, Ted Ts'o wrote:
> On Wed, Oct 27, 2010 at 05:16:18PM -0700, David Daney wrote:
>> Tracing is supposed to be low overhead.  Forcing people to decode
>> things like this at the trace point, may take more code and cause
>> the trace data to be larger, making it slower than necessary.
>>
>> If there isn't a good reason to keep perf stupid, then making it
>> smarter could be attractive.
>
> Agreed.  Although one argument against making perf smarter is that
> certain things such as the dev_t MAJOR/MINOR split is an internal
> abstraction that could potentially vary from kernel to kernel.
>
> And the question is whether perf really should be so different that if
> you boot a different kernel, you had better have the right perf
> installed.
>

It may be possible to encode the dev_t split in the trace meta-data. 
This is done for some other types.  Then perf could decode it based on 
the meta-data.

Another option is to have perf print the raw data and not crash.  Then 
someone looking at the output could, if they desired, decode the dev_t 
themselves.

David Daney

Re: Perf can't deal with many tracepoints

[Frank Ch. Eigler]

"Theodore Ts'o" <tytso@mit.edu> writes:

> Perf will drop dead if it comes across tracepoints that have anything
> but primitive structure accessors in the TP_printk() section of the
> tracepoint definition.  For example, the ext4 and jbd2 tracepoints uses
> jbd2_dev_to_name() to translate a dev_t to a string.  

In the mean time, you may enjoy:

# stap -L 'kernel.trace("*")'
# stap -g -e '
%{
#include<linux/jbd2.h> 
%}
function jbd2name(dev) %{
   strlcpy(THIS->__retvalue, jbd2_dev_to_name(THIS->dev), MAXSTRINGLEN);
%}
probe kernel.trace("ext4_free_inode") {
   log(jbd2name($inode->i_sb->s_dev)) 
}'


> The block I/O tracepoints uses MAJOR() and MINOR() to translate a
> dev_t to a major/minor number pair.  [...]

(Similarly for this case.)


- FChE