Messages in this thread | | | Date | Wed, 6 Nov 2013 15:31:02 -0500 | From | Mike Snitzer <> | Subject | Re: block: Revert bio_clone() default behaviour |
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Hey Kent,
Digging a bit in the LKML archive I think this patch is in response to this thread: https://lkml.org/lkml/2013/11/6/27
Might be good to give context for which reported problem(s) are being fixed by this patch.
On Tue, Nov 05 2013 at 10:48pm -0500, Kent Overstreet <kmo@daterainc.com> wrote:
> This patch reverts the default behaviour introduced by > 9fc6286f347d00528adcdcf12396d220f47492ed - bio_clone_biovec() no clonger > shares the source bio's biovec, cloning the biovec is once again the > default.
Your focus, in terms of revert, seems to be on restoring bio_clone_bioset, so: s/bio_clone_biovec/bio_clone_bioset/
Maybe best to say "effectively reverts" since you aren't reverting 9fc6286f347d00528adcdcf12396d220f47492ed ? Also s/clonger/longer/ typo ^
> Instead, we add a new bio_clone_biovec_fast(), which creates a clone > that shares the source's biovec. This patch changes bcache and md to use
s/md/dm/
> __bio_clone_biovec_fast() since they're expecting the new behaviour due > to other refactoring; most of the other uses of bio_clone() should be > same to convert to the _fast() variant but that will be done more
s/same/safe/
> incrementally in other patches (bio_split() in particular). > > Note that __bio_clone() isn't being readded - the reason being that with > immutable biovecs allocating the right number of biovecs for the new > clone is no longer trivial so we don't want drivers trying to do that > themselves. > > This patch also reverts febca1baea1cfe2d7a0271385d89b03d5fb34f94 - > __bio_clone_fast() should not be setting bi_vcnt for bios that do not > own the biovec (see Documentation/block/biovecs.txt for rationale) - in > short, not setting it might cause bugs in the short term but long term > it's likely to hide nastier more subtle bugs, we don't want code looking > at bi_vcnt at all for bios it does not own. However, this patch > _shouldn't_ cause any regressions because of this since we're reverting > back to the old bio_clone() behaviour. > > Signed-off-by: Kent Overstreet <kmo@daterainc.com> > Cc: Jens Axboe <axboe@kernel.dk> > Cc: Chris Mason <chris.mason@fusionio.com> > Cc: Mike Snitzer <snitzer@redhat.com> > Cc: NeilBrown <neilb@suse.de> > Cc: Olof Johansson <olof@lixom.net> > --- > Chris, Olaf, can you two in particular test this? I have tested the bounce > buffer code (and bcache), but Jens told me today there was an md bug that I > _still_ can't find any emails about so I'm not sure what to test for that.
/me assumes you really mean md here, given Chris's later reply in this thread.
Relative to DM, this patch looks fine to me:
Acked-by: Mike Snitzer <snitzer@redhat.com>
Thanks, Mike
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