Messages in this thread | | | Date | Thu, 9 Aug 2012 19:29:04 -0700 | Subject | Re: [dm-devel] [PATCH v5 12/12] block: Only clone bio vecs that are in use | From | Muthu Kumar <> |
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Tejun,
On Thu, Aug 9, 2012 at 12:01 AM, Tejun Heo <tj@kernel.org> 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.
Regards, Muthu
> > Thanks. > > -- > tejun
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