The Linux Manuals (man pages) document is an important part of Linux documents. Linux Manuals are organized as several sections. Each section has a group of commands for a specific area in Linux usage, administration or development.
blk_rq_map_user_iov – map user data to a request, for REQ_TYPE_BLOCK_PC usage Synopsis int blk_rq_map_user_iov(struct request_queue *q, struct request *rq, struct rq_map_data *map_data, const struct iov_iter *iter, gfp_t gfp_mask); Arguments q request queue where request should be inserted rq request to map data to map_data pointer to the rq_map_data holding pages (if necessary) iter iovec iterator…
blk_rq_map_kern – map kernel data to a request, for REQ_TYPE_BLOCK_PC usage Synopsis int blk_rq_map_kern(struct request_queue *q, struct request *rq, void *kbuf, unsigned int len, gfp_t gfp_mask); Arguments q request queue where request should be inserted rq request to fill kbuf the kernel buffer len length of user data gfp_mask memory allocation flags Description Data will…
blk_rq_map_integrity_sg – Map integrity metadata into a scatterlist Synopsis int blk_rq_map_integrity_sg(struct request_queue *q, struct bio *bio, struct scatterlist *sglist); Arguments q request queue bio bio with integrity metadata attached sglist target scatterlist Description Map the integrity vectors in request into a scatterlist. The scatterlist must be big enough to hold all elements. I.e. sized using…
blk_rq_err_bytes – determine number of bytes till the next failure boundary Synopsis unsigned int blk_rq_err_bytes(const struct request *rq); Arguments rq request to examine Description A request could be merge of IOs which require different failure handling. This function determines the number of bytes which can be failed from the beginning of the request without crossing…
blk_rq_count_integrity_sg – Count number of integrity scatterlist elements Synopsis int blk_rq_count_integrity_sg(struct request_queue *q, struct bio *bio); Arguments q request queue bio bio with integrity metadata attached Description Returns the number of elements required in a scatterlist corresponding to the integrity metadata in a bio. Copyright
blk_requeue_request – put a request back on queue Synopsis void blk_requeue_request(struct request_queue *q, struct request *rq); Arguments q request queue where request should be inserted rq request to be inserted Description Drivers often keep queueing requests until the hardware cannot accept more, when that condition happens we need to put the request back on the…
blk_release_queue – release a struct request_queue when it is no longer needed Synopsis void blk_release_queue(struct kobject *kobj); Arguments kobj the kobj belonging to the request queue to be released Description blk_release_queue is the pair to blk_init_queue or blk_queue_make_request. It should be called when a request queue is being released; typically when a block device is…
blk_queue_write_cache – configure queue’s write cache Synopsis void blk_queue_write_cache(struct request_queue *q, bool wc, bool fua); Arguments q the request queue for the device wc write back cache on or off fua device supports FUA writes, if true Description Tell the block layer about the write cache of q. Copyright
blk_queue_virt_boundary – set boundary rules for bio merging Synopsis void blk_queue_virt_boundary(struct request_queue *q, unsigned long mask); Arguments q the request queue for the device mask the memory boundary mask Copyright
blk_queue_update_dma_pad – update pad mask Synopsis void blk_queue_update_dma_pad(struct request_queue *q, unsigned int mask); Arguments q the request queue for the device mask pad mask Description Update 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_update_dma_alignment – update dma length and memory alignment Synopsis void blk_queue_update_dma_alignment(struct request_queue *q, int mask); Arguments q the request queue for the device mask alignment mask Description update required memory and length alignment for direct dma transactions. If the requested alignment is larger than the current alignment, then the current queue alignment is updated to…
blk_queue_unprep_rq – set an unprepare_request function for queue Synopsis void blk_queue_unprep_rq(struct request_queue *q, unprep_rq_fn *ufn); Arguments q queue ufn unprepare_request function Description It’s possible for a queue to register an unprepare_request callback which is invoked before the request is finally completed. The goal of the function is to deallocate any data that was allocated in…
blk_queue_start_tag – find a free tag and assign it Synopsis int blk_queue_start_tag(struct request_queue *q, struct request *rq); Arguments q the request queue for the device rq the block request that needs tagging Description This can either be used as a stand-alone helper, or possibly be assigned as the queue prep_rq_fn (in which case struct request…
blk_queue_stack_limits – inherit underlying queue limits for stacked drivers Synopsis void blk_queue_stack_limits(struct request_queue *t, struct request_queue *b); Arguments t the stacking driver (top) b the underlying device (bottom) Copyright
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