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Documentation: update notes in biovecs about arbitrarily sized bios 

Update block/biovecs.txt so that it includes a note on what kind of
effects arbitrarily sized bios would bring to the block layer.
Also fix a trivial typo, bio_iter_iovec.

Cc: Christoph Hellwig <hch@infradead.org>
Cc: Kent Overstreet <kent.overstreet@gmail.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: linux-doc@vger.kernel.org
Signed-off-by: Dongsu Park <dpark@posteo.net>
Signed-off-by: Ming Lin <ming.l@ssi.samsung.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
This commit is contained in:
Dongsu Park 2014-12-19 14:53:03 +01:00 committed by Jens Axboe
parent b54ffb73ca
commit 2ec3182f9c
1 changed files with 9 additions and 1 deletions
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Documentation/block/biovecs.txt
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@ -24,7 +24,7 @@ particular, presenting the illusion of partially completed biovecs so that
normal code doesn't have to deal with bi_bvec_done.
* Driver code should no longer refer to biovecs directly; we now have
bio_iovec() and bio_iovec_iter() macros that return literal struct biovecs,
bio_iovec() and bio_iter_iovec() macros that return literal struct biovecs,
constructed from the raw biovecs but taking into account bi_bvec_done and
bi_size.
@ -109,3 +109,11 @@ Other implications:
over all the biovecs in the new bio - which is silly as it's not needed.
So, don't use bi_vcnt anymore.
* The current interface allows the block layer to split bios as needed, so we
could eliminate a lot of complexity particularly in stacked drivers. Code
that creates bios can then create whatever size bios are convenient, and
more importantly stacked drivers don't have to deal with both their own bio
size limitations and the limitations of the underlying devices. Thus
there's no need to define ->merge_bvec_fn() callbacks for individual block
drivers.