blk_queue_segment_boundary – set boundary rules for segment merging Synopsis void blk_queue_segment_boundary(struct request_queue *q, unsigned long mask); Arguments q the request queue for the device mask the memory boundary mask Copyright
blk_queue_resize_tags – change the queueing depth Synopsis int blk_queue_resize_tags(struct request_queue *q, int new_depth); Arguments q the request queue for the device new_depth the new max command queueing depth Notes Must be called with the queue lock held. Copyright
blk_queue_prep_rq – set a prepare_request function for queue Synopsis void blk_queue_prep_rq(struct request_queue *q, prep_rq_fn *pfn); Arguments q queue pfn prepare_request function Description It’s possible for a queue to register a prepare_request callback which is invoked before the request is handed to the request_fn. The goal of the function is to prepare a request for I/O,…
blk_queue_physical_block_size – set physical block size for the queue Synopsis void blk_queue_physical_block_size(struct request_queue *q, unsigned int size); Arguments q the request queue for the device size the physical block size, in bytes Description This should be set to the lowest possible sector size that the hardware can operate on without reverting to read-modify-write operations. Copyright
blk_queue_max_write_same_sectors – set max sectors for a single write same Synopsis void blk_queue_max_write_same_sectors(struct request_queue *q, unsigned int max_write_same_sectors); Arguments q the request queue for the device max_write_same_sectors maximum number of sectors to write per command Copyright
blk_queue_max_segments – set max hw segments for a request for this queue Synopsis void blk_queue_max_segments(struct request_queue *q, unsigned short max_segments); Arguments q the request queue for the device max_segments max number of segments Description Enables a low level driver to set an upper limit on the number of hw data segments in a request. Copyright
blk_queue_max_segment_size – set max segment size for blk_rq_map_sg Synopsis void blk_queue_max_segment_size(struct request_queue *q, unsigned int max_size); Arguments q the request queue for the device max_size max size of segment in bytes Description Enables a low level driver to set an upper limit on the size of a coalesced segment Copyright
blk_queue_max_hw_sectors – set max sectors for a request for this queue Synopsis void blk_queue_max_hw_sectors(struct request_queue *q, unsigned int max_hw_sectors); Arguments q the request queue for the device max_hw_sectors max hardware sectors in the usual 512b unit Description Enables a low level driver to set a hard upper limit, max_hw_sectors, on the size of requests. max_hw_sectors…
blk_queue_max_discard_sectors – set max sectors for a single discard Synopsis void blk_queue_max_discard_sectors(struct request_queue *q, unsigned int max_discard_sectors); Arguments q the request queue for the device max_discard_sectors maximum number of sectors to discard Copyright
blk_queue_make_request – define an alternate make_request function for a device Synopsis void blk_queue_make_request(struct request_queue *q, make_request_fn *mfn); Arguments q the request queue for the device to be affected mfn the alternate make_request function Description The normal way for struct bios to be passed to a device driver is for them to be collected into requests…
blk_queue_logical_block_size – set logical block size for the queue Synopsis void blk_queue_logical_block_size(struct request_queue *q, unsigned short size); Arguments q the request queue for the device size the logical block size, in bytes Description This should be set to the lowest possible block size that the storage device can address. The default of 512 covers most…
blk_queue_io_opt – set optimal request size for the queue Synopsis void blk_queue_io_opt(struct request_queue *q, unsigned int opt); Arguments q the request queue for the device opt optimal request size in bytes Description Storage devices may report an optimal I/O size, which is the device’s preferred unit for sustained I/O. This is rarely reported for disk…
blk_queue_io_min – set minimum request size for the queue Synopsis void blk_queue_io_min(struct request_queue *q, unsigned int min); Arguments q the request queue for the device min smallest I/O size in bytes Description Storage devices may report a granularity or preferred minimum I/O size which is the smallest request the device can perform without incurring a…
blk_queue_invalidate_tags – invalidate all pending tags Synopsis void blk_queue_invalidate_tags(struct request_queue *q); Arguments q the request queue for the device Description Hardware conditions may dictate a need to stop all pending requests. In this case, we will safely clear the block side of the tag queue and readd all requests to the request queue in the…
blk_queue_init_tags – initialize the queue tag info Synopsis int blk_queue_init_tags(struct request_queue *q, int depth, struct blk_queue_tag *tags, int alloc_policy); Arguments q the request queue for the device depth the maximum queue depth supported tags the tag to use alloc_policy tag allocation policy Description Queue lock must be held here if the function is called to…
blk_queue_free_tags – release tag maintenance info Synopsis void blk_queue_free_tags(struct request_queue *q); Arguments q the request queue for the device Notes This is used to disable tagged queuing to a device, yet leave queue in function. Copyright
blk_queue_find_tag – find a request by its tag and queue Synopsis struct request *blk_queue_find_tag(struct request_queue *q, int tag); Arguments q The request queue for the device tag The tag of the request Notes Should be used when a device returns a tag and you want to match it with a request. no locks need be…
blk_queue_end_tag – end tag operations for a request Synopsis void blk_queue_end_tag(struct request_queue *q, struct request *rq); Arguments q the request queue for the device rq the request that has completed Description Typically called when end_that_request_first returns 0, meaning all transfers have been done for a request. It’s important to call this function before end_that_request_last, as…
blk_queue_dma_pad – set pad mask Synopsis void blk_queue_dma_pad(struct request_queue *q, unsigned int mask); Arguments q the request queue for the device mask pad mask Description Set dma pad mask. Appending pad buffer to a request modifies the last entry of a scatter list such that it includes the pad buffer. Copyright
blk_queue_dma_drain – Set up a drain buffer for excess dma. Synopsis int blk_queue_dma_drain(struct request_queue *q, dma_drain_needed_fn *dma_drain_needed, void *buf, unsigned int size); Arguments q the request queue for the device dma_drain_needed fn which returns non-zero if drain is necessary buf physically contiguous buffer size size of the buffer in bytes Description Some devices have excess…