[lkml]   [2012]   [Aug]   [9]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [dm-devel] [PATCH v5 12/12] block: Only clone bio vecs that are in use

On Thu, Aug 9, 2012 at 12:01 AM, Tejun Heo <> wrote:
> Hello,
> On Wed, Aug 08, 2012 at 04:47:46PM -0700, Muthu Kumar wrote:
>> You are changing the meaning of __bio_clone() here. In old code, the
>> number of io_vecs, bi_idx, bi_vcnt are preserved. But in this modified
>> code, you are mapping bio_src's bi_iovec[bi_idx] to bio_dests
>> bi_iovec[0] and also restricting the number of allocated io_vecs of
>> the clone. It may be useful for cases were we would like a identical
>> copy of the original bio (may not be in current code base, but this
>> implementation is definitely not what one would expect from the name
>> "clone").
> Implementation details changed somewhat but the high-level semantics
> didn't change at all. Any driver not messing with bio internals - and
> they shouldn't - shouldn't notice the change.

The reason for doing this change is because the code in question is
messing with bio internals.

No in-kernel drivers
> seem to be broken by the change. If you ask me, this looks more like
> a bug fix to me where the bug is a silly behavior restricting
> usefulness of the interface.
>> May be, call this new implementation some thing else (and use it for bcache)?
> This doesn't only change __bio_clone() but all clone interface stacked
> on top of it, so, no way.

>This ain't windows.

ah... when you put it this way, it gets a different perspective :)

Anyway, my point is, we shouldn't make it non-obvious ("clone" should
be just "clone"). But, we can always add more comments i guess.


> Thanks.
> --
> tejun

 \ /
  Last update: 2012-08-10 05:01    [W:0.101 / U:5.084 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site