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

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Date:   Thu, 18 Apr 2019 12:44:08 +0200
From:   Alexander Potapenko <glider@...gle.com>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>, x86@...nel.org,
        Andy Lutomirski <luto@...nel.org>,
        Steven Rostedt <rostedt@...dmis.org>, dm-devel@...hat.com,
        Mike Snitzer <snitzer@...hat.com>,
        Alasdair Kergon <agk@...hat.com>,
        Alexey Dobriyan <adobriyan@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Pekka Enberg <penberg@...nel.org>,
        Linux Memory Management List <linux-mm@...ck.org>,
        David Rientjes <rientjes@...gle.com>,
        Christoph Lameter <cl@...ux.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        kasan-dev <kasan-dev@...glegroups.com>,
        Mike Rapoport <rppt@...ux.vnet.ibm.com>,
        Akinobu Mita <akinobu.mita@...il.com>,
        iommu@...ts.linux-foundation.org,
        Robin Murphy <robin.murphy@....com>,
        Christoph Hellwig <hch@....de>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Johannes Thumshirn <jthumshirn@...e.de>,
        David Sterba <dsterba@...e.com>, Chris Mason <clm@...com>,
        Josef Bacik <josef@...icpanda.com>,
        linux-btrfs@...r.kernel.org, intel-gfx@...ts.freedesktop.org,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        dri-devel@...ts.freedesktop.org, David Airlie <airlied@...ux.ie>,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        linux-arch@...r.kernel.org
Subject: Re: [patch V2 14/29] dm bufio: Simplify stack trace retrieval

On Thu, Apr 18, 2019 at 11:06 AM Thomas Gleixner <tglx@...utronix.de> wrote:
>
> Replace the indirection through struct stack_trace with an invocation of
> the storage array based interface.
>
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
> Cc: dm-devel@...hat.com
> Cc: Mike Snitzer <snitzer@...hat.com>
> Cc: Alasdair Kergon <agk@...hat.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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