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_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…
blk_queue_dma_alignment – set dma length and memory alignment Synopsis void blk_queue_dma_alignment(struct request_queue *q, int mask); Arguments q the request queue for the device mask alignment mask Description set required memory and length alignment for direct dma transactions. this is used when building direct io requests for the queue. Copyright
blk_queue_chunk_sectors – set size of the chunk for this queue Synopsis void blk_queue_chunk_sectors(struct request_queue *q, unsigned int chunk_sectors); Arguments q the request queue for the device chunk_sectors chunk sectors in the usual 512b unit Description If a driver doesn’t want IOs to cross a given chunk size, it can set this limit and prevent merging…
blk_queue_bypass_start – enter queue bypass mode Synopsis void blk_queue_bypass_start(struct request_queue *q); Arguments q queue of interest Description In bypass mode, only the dispatch FIFO queue of q is used. This function makes q enter bypass mode and drains all requests which were throttled or issued before. On return, it’s guaranteed that no request is being…
blk_queue_bypass_end – leave queue bypass mode Synopsis void blk_queue_bypass_end(struct request_queue *q); Arguments q queue of interest Description Leave bypass mode and restore the normal queueing behavior. Copyright
blk_queue_bounce_limit – set bounce buffer limit for queue Synopsis void blk_queue_bounce_limit(struct request_queue *q, u64 max_addr); Arguments q the request queue for the device max_addr the maximum address the device can handle Description Different hardware can have different requirements as to what pages it can do I/O directly to. A low level driver can call blk_queue_bounce_limit…
blk_queue_alignment_offset – set physical block alignment offset Synopsis void blk_queue_alignment_offset(struct request_queue *q, unsigned int offset); Arguments q the request queue for the device offset alignment offset in bytes Description Some devices are naturally misaligned to compensate for things like the legacy DOS partition table 63-sector offset. Low-level drivers should call this function for devices whose…