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authorChristoph Hellwig <hch@lst.de>2016-12-08 15:20:32 -0700
committerJens Axboe <axboe@fb.com>2016-12-09 08:30:51 -0700
commitf9d03f96b988002027d4b28ea1b7a24729a4c9b5 (patch)
treee4995a30bbe58290594e2ef29de5ae2785c6c9db /include/linux/blk-mq.h
parentbe07e14f96e3121483339a64d917fddb3b86ba98 (diff)
block: improve handling of the magic discard payload
Instead of allocating a single unused biovec for discard requests, send them down without any payload. Instead we allow the driver to add a "special" payload using a biovec embedded into struct request (unioned over other fields never used while in the driver), and overloading the number of segments for this case. This has a couple of advantages: - we don't have to allocate the bio_vec - the amount of special casing for discard requests in the block layer is significantly reduced - using this same scheme for other request types is trivial, which will be important for implementing the new WRITE_ZEROES op on devices where it actually requires a payload (e.g. SCSI) - we can get rid of playing games with the request length, as we'll never touch it and completions will work just fine - it will allow us to support ranged discard operations in the future by merging non-contiguous discard bios into a single request - last but not least it removes a lot of code This patch is the common base for my WIP series for ranges discards and to remove discard_zeroes_data in favor of always using REQ_OP_WRITE_ZEROES, so it would be good to get it in quickly. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <axboe@fb.com>
Diffstat (limited to 'include/linux/blk-mq.h')
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