forked from luck/tmp_suning_uos_patched
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>
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@ -24,7 +24,7 @@ particular, presenting the illusion of partially completed biovecs so that
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normal code doesn't have to deal with bi_bvec_done.
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* Driver code should no longer refer to biovecs directly; we now have
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bio_iovec() and bio_iovec_iter() macros that return literal struct biovecs,
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bio_iovec() and bio_iter_iovec() macros that return literal struct biovecs,
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constructed from the raw biovecs but taking into account bi_bvec_done and
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bi_size.
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@ -109,3 +109,11 @@ Other implications:
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over all the biovecs in the new bio - which is silly as it's not needed.
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So, don't use bi_vcnt anymore.
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* The current interface allows the block layer to split bios as needed, so we
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could eliminate a lot of complexity particularly in stacked drivers. Code
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that creates bios can then create whatever size bios are convenient, and
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more importantly stacked drivers don't have to deal with both their own bio
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size limitations and the limitations of the underlying devices. Thus
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there's no need to define ->merge_bvec_fn() callbacks for individual block
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drivers.
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