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Re: [PATCH] block: don't make BLK_DEF_MAX_SECTORS too big

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On Tue, Mar 29, 2016 at 09:42:33AM -0700, Shaohua Li wrote:
> bio_alloc_bioset() allocates bvecs from bvec_slabs which can only
> allocate maximum 256 bvec (eg, 1M for 4k pages). We can't bump
> BLK_DEF_MAX_SECTORS to exceed this value otherwise bio_alloc_bioset will
> fail.

This might be true, but it's not a good enough reason.  Request based
driver couldn't care less about the limits of bio_alloc_bioset.

It seems the bug is that somone (would be great to know whoe exactly)
passes a too large value to bio_alloc_bioset. And given that we still
have bio_add_page around for actually adding pages to a bio it seems
like the proper fix would be to simply clamp down the actual allocation
and segment limit inside bio_alloc_bioset.  Which would also help to
eventually remove code doing just that in tons of callers.

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Thread

[PATCH] block: don't make BLK_DEF_MAX_SECTORS too big Shaohua Li <shli@fb.com> - 2016-03-29 18:50 +0200
  Re: [PATCH] block: don't make BLK_DEF_MAX_SECTORS too big Christoph Hellwig <hch@infradead.org> - 2016-03-29 23:20 +0200
    Re: [PATCH] block: don't make BLK_DEF_MAX_SECTORS too big Shaohua Li <shli@fb.com> - 2016-03-30 00:10 +0200
      Re: [PATCH] block: don't make BLK_DEF_MAX_SECTORS too big Christoph Hellwig <hch@infradead.org> - 2016-03-30 09:00 +0200
        Re: [PATCH] block: don't make BLK_DEF_MAX_SECTORS too big Shaohua Li <shli@fb.com> - 2016-03-30 19:00 +0200
          Re: [PATCH] block: don't make BLK_DEF_MAX_SECTORS too big Christoph Hellwig <hch@infradead.org> - 2016-03-30 19:50 +0200
          Re: [PATCH] block: don't make BLK_DEF_MAX_SECTORS too big Kent Overstreet <kent.overstreet@gmail.com> - 2016-03-31 03:00 +0200
  Re: [PATCH] block: don't make BLK_DEF_MAX_SECTORS too big Ming Lei <ming.lei@canonical.com> - 2016-03-30 03:40 +0200
    Re: [PATCH] block: don't make BLK_DEF_MAX_SECTORS too big Shaohua Li <shli@fb.com> - 2016-03-30 04:30 +0200
      Re: [PATCH] block: don't make BLK_DEF_MAX_SECTORS too big Ming Lei <ming.lei@canonical.com> - 2016-03-30 14:20 +0200
        Re: [PATCH] block: don't make BLK_DEF_MAX_SECTORS too big Shaohua Li <shli@fb.com> - 2016-03-30 19:10 +0200
          Re: [PATCH] block: don't make BLK_DEF_MAX_SECTORS too big Ming Lei <ming.lei@canonical.com> - 2016-03-31 02:50 +0200

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