From mboxrd@z Thu Jan  1 00:00:00 1970
From: Vivek Goyal <vgoyal@redhat.com>
Subject: Re: [PATCH RFCv2 03/10] dm-dedup: hash computation
Date: Fri, 6 Feb 2015 16:42:07 -0500
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Cc: Joe Thornber <thornber@redhat.com>, Mike Snitzer <snitzer@redhat.com>, Christoph Hellwig <hch@infradead.org>, Philip Shilane <philip.shilane@emc.com>, Sonam Mandal <sonam.dp42@gmail.com>, Erez Zadok <ezk@fsl.cs.sunysb.edu>
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On Thu, Aug 28, 2014 at 06:04:55PM -0400, Vasily Tarasov wrote:

[..]
> +#include "dm-dedup-target.h"
> +#include "dm-dedup-hash.h"
> +#include <linux/atomic.h>
> +#include <linux/blk_types.h>
> +
> +/*
> + * We are declaring and initalizaing global hash_desc, because
> + * we need to do hash computation in endio function, and this
> + * function is called in softirq context. Hence we are not
> + * allowed to perform any operation on that path which can sleep.
> + * And tfm allocation in hash_desc, at one point, tries to take
> + * semaphore and hence tries to sleep. And because of this we get
> + * BUG, which complains "Scheduling while atomic". Hence to avoid
> + * this scenario, we moved the declaration and initialization out
> + * of critical path.
> + */

Hi,

Is this comment still valid? We calculate hash when bio is submitted
from the worker thread context. So where is the softirq context here?

do_work()
 process_bio()
  handle_write()
   compute_hash_bio()

This all is happening in worker worker thread context and not softirq
context?

Thanks
Vivek