[V2,14/29] dm bufio: Simplify stack trace retrieval
diff mbox series

Message ID 20190418084254.361284697@linutronix.de
State New
Headers show
Series
  • stacktrace: Consolidate stack trace usage
Related show

Commit Message

Thomas Gleixner April 18, 2019, 8:41 a.m. UTC
Replace the indirection through struct stack_trace with an invocation of
the storage array based interface.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: dm-devel@redhat.com
Cc: Mike Snitzer <snitzer@redhat.com>
Cc: Alasdair Kergon <agk@redhat.com>
---
 drivers/md/dm-bufio.c |   15 ++++++---------
 1 file changed, 6 insertions(+), 9 deletions(-)

Comments

Alexander Potapenko April 18, 2019, 10:44 a.m. UTC | #1
On Thu, Apr 18, 2019 at 11:06 AM Thomas Gleixner <tglx@linutronix.de> wrote:
>
> Replace the indirection through struct stack_trace with an invocation of
> the storage array based interface.
>
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> Cc: dm-devel@redhat.com
> Cc: Mike Snitzer <snitzer@redhat.com>
> Cc: Alasdair Kergon <agk@redhat.com>
> ---
>  drivers/md/dm-bufio.c |   15 ++++++---------
>  1 file changed, 6 insertions(+), 9 deletions(-)
>
> --- a/drivers/md/dm-bufio.c
> +++ b/drivers/md/dm-bufio.c
> @@ -150,7 +150,7 @@ struct dm_buffer {
>         void (*end_io)(struct dm_buffer *, blk_status_t);
>  #ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING
>  #define MAX_STACK 10
> -       struct stack_trace stack_trace;
> +       unsigned int stack_len;
>         unsigned long stack_entries[MAX_STACK];
>  #endif
>  };
> @@ -232,11 +232,7 @@ static DEFINE_MUTEX(dm_bufio_clients_loc
>  #ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING
>  static void buffer_record_stack(struct dm_buffer *b)
>  {
> -       b->stack_trace.nr_entries = 0;
> -       b->stack_trace.max_entries = MAX_STACK;
> -       b->stack_trace.entries = b->stack_entries;
> -       b->stack_trace.skip = 2;
> -       save_stack_trace(&b->stack_trace);
> +       b->stack_len = stack_trace_save(b->stack_entries, MAX_STACK, 2);
As noted in one of similar patches before, can we have an inline
comment to indicate what does this "2" stand for?
>  }
>  #endif
>
> @@ -438,7 +434,7 @@ static struct dm_buffer *alloc_buffer(st
>         adjust_total_allocated(b->data_mode, (long)c->block_size);
>
>  #ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING
> -       memset(&b->stack_trace, 0, sizeof(b->stack_trace));
> +       b->stack_len = 0;
>  #endif
>         return b;
>  }
> @@ -1520,8 +1516,9 @@ static void drop_buffers(struct dm_bufio
>                         DMERR("leaked buffer %llx, hold count %u, list %d",
>                               (unsigned long long)b->block, b->hold_count, i);
>  #ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING
> -                       print_stack_trace(&b->stack_trace, 1);
> -                       b->hold_count = 0; /* mark unclaimed to avoid BUG_ON below */
> +                       stack_trace_print(b->stack_entries, b->stack_len, 1);
> +                       /* mark unclaimed to avoid BUG_ON below */
> +                       b->hold_count = 0;
>  #endif
>                 }
>
>
>
Thomas Gleixner April 18, 2019, 11:54 a.m. UTC | #2
On Thu, 18 Apr 2019, Alexander Potapenko wrote:
> On Thu, Apr 18, 2019 at 11:06 AM Thomas Gleixner <tglx@linutronix.de> wrote:
> > -       save_stack_trace(&b->stack_trace);
> > +       b->stack_len = stack_trace_save(b->stack_entries, MAX_STACK, 2);
> As noted in one of similar patches before, can we have an inline
> comment to indicate what does this "2" stand for?

Come on. We have gazillion of functions which take numerical constant
arguments. Should we add comments to all of them?

Thanks,

	tglx
Alexander Potapenko April 18, 2019, 12:11 p.m. UTC | #3
On Thu, Apr 18, 2019 at 1:54 PM Thomas Gleixner <tglx@linutronix.de> wrote:
>
> On Thu, 18 Apr 2019, Alexander Potapenko wrote:
> > On Thu, Apr 18, 2019 at 11:06 AM Thomas Gleixner <tglx@linutronix.de> wrote:
> > > -       save_stack_trace(&b->stack_trace);
> > > +       b->stack_len = stack_trace_save(b->stack_entries, MAX_STACK, 2);
> > As noted in one of similar patches before, can we have an inline
> > comment to indicate what does this "2" stand for?
>
> Come on. We have gazillion of functions which take numerical constant
> arguments. Should we add comments to all of them?
Ok, sorry. I might not be familiar enough with the kernel style guide.
> Thanks,
>
>         tglx
Steven Rostedt April 18, 2019, 1:33 p.m. UTC | #4
On Thu, 18 Apr 2019 14:11:44 +0200
Alexander Potapenko <glider@google.com> wrote:

> On Thu, Apr 18, 2019 at 1:54 PM Thomas Gleixner <tglx@linutronix.de> wrote:
> >
> > On Thu, 18 Apr 2019, Alexander Potapenko wrote:  
> > > On Thu, Apr 18, 2019 at 11:06 AM Thomas Gleixner <tglx@linutronix.de> wrote:  
> > > > -       save_stack_trace(&b->stack_trace);
> > > > +       b->stack_len = stack_trace_save(b->stack_entries, MAX_STACK, 2);  
> > > As noted in one of similar patches before, can we have an inline
> > > comment to indicate what does this "2" stand for?  
> >
> > Come on. We have gazillion of functions which take numerical constant
> > arguments. Should we add comments to all of them?  
> Ok, sorry. I might not be familiar enough with the kernel style guide.

It is a legitimate complaint but not for this series. I only complain
about hard coded constants when they are added. That "2" was not
added by this series. This patch set is a clean up of the stack tracing
code, not a clean up of removing hard coded constants, or commenting
them.

The hard coded "2" was there without a comment before this patch series
and Thomas is correct to leave it as is for these changes. This patch
series should not modify what was already there which is out of scope
for the purpose of these changes.

A separate clean up patch to the maintainer of the subsystem (dm bufio
in this case) is fine. But it's not Thomas's responsibility.

-- Steve

Patch
diff mbox series

--- a/drivers/md/dm-bufio.c
+++ b/drivers/md/dm-bufio.c
@@ -150,7 +150,7 @@  struct dm_buffer {
 	void (*end_io)(struct dm_buffer *, blk_status_t);
 #ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING
 #define MAX_STACK 10
-	struct stack_trace stack_trace;
+	unsigned int stack_len;
 	unsigned long stack_entries[MAX_STACK];
 #endif
 };
@@ -232,11 +232,7 @@  static DEFINE_MUTEX(dm_bufio_clients_loc
 #ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING
 static void buffer_record_stack(struct dm_buffer *b)
 {
-	b->stack_trace.nr_entries = 0;
-	b->stack_trace.max_entries = MAX_STACK;
-	b->stack_trace.entries = b->stack_entries;
-	b->stack_trace.skip = 2;
-	save_stack_trace(&b->stack_trace);
+	b->stack_len = stack_trace_save(b->stack_entries, MAX_STACK, 2);
 }
 #endif
 
@@ -438,7 +434,7 @@  static struct dm_buffer *alloc_buffer(st
 	adjust_total_allocated(b->data_mode, (long)c->block_size);
 
 #ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING
-	memset(&b->stack_trace, 0, sizeof(b->stack_trace));
+	b->stack_len = 0;
 #endif
 	return b;
 }
@@ -1520,8 +1516,9 @@  static void drop_buffers(struct dm_bufio
 			DMERR("leaked buffer %llx, hold count %u, list %d",
 			      (unsigned long long)b->block, b->hold_count, i);
 #ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING
-			print_stack_trace(&b->stack_trace, 1);
-			b->hold_count = 0; /* mark unclaimed to avoid BUG_ON below */
+			stack_trace_print(b->stack_entries, b->stack_len, 1);
+			/* mark unclaimed to avoid BUG_ON below */
+			b->hold_count = 0;
 #endif
 		}