Re: [patch V2 14/29] dm bufio: Simplify stack trace retrieval

Alexander Potapenko via iommu
2019-04-18T12:45:21Z

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
> }
>
>
>

--
Alexander Potapenko
Software Engineer

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