TRACE_BLOCK_GETRQ(9) Block IO TRACE_BLOCK_GETRQ(9)NAME
trace_block_getrq - get a free request entry in queue for block IO operations
void trace_block_getrq(struct request_queue * q, struct bio * bio, int rw);
queue for operations
pending block IO operation
low bit indicates a read (0) or a write (1)
A request struct for queue q has been allocated to handle the block IO operation bio.
Jason Baron <firstname.lastname@example.org>
William Cohen <email@example.com>
COPYRIGHT Kernel Hackers Manual 3.10 June 2014 TRACE_BLOCK_GETRQ(9)
Check Out this Related Man Page
BLK_MAKE_REQUEST(9) Block Devices BLK_MAKE_REQUEST(9)NAME
blk_make_request - given a bio, allocate a corresponding struct request.
struct request * blk_make_request(struct request_queue * q, struct bio * bio, gfp_t gfp_mask);
target request queue
The bio describing the memory mappings that will be submitted for IO. It may be a chained-bio properly constructed by block/bio layer.
gfp flags to be used for memory allocation
blk_make_request is the parallel of generic_make_request for BLOCK_PC type commands. Where the struct request needs to be farther
initialized by the caller. It is passed a struct bio, which describes the memory info of the I/O transfer.
The caller of blk_make_request must make sure that bi_io_vec are set to describe the memory buffers. That bio_data_dir will return the
needed direction of the request. (And all bio's in the passed bio-chain are properly set accordingly)
If called under none-sleepable conditions, mapped bio buffers must not need bouncing, by calling the appropriate masked or flagged
allocator, suitable for the target device. Otherwise the call to blk_queue_bounce will BUG.
When allocating/cloning a bio-chain, careful consideration should be given to how you allocate bios. In particular, you cannot use
__GFP_WAIT for anything but the first bio in the chain. Otherwise you risk waiting for IO completion of a bio that hasn't been submitted
yet, thus resulting in a deadlock. Alternatively bios should be allocated using bio_kmalloc instead of bio_alloc, as that avoids the
mempool deadlock. If possible a big IO should be split into smaller parts when allocation fails. Partial allocation should not be an error,
or you risk a live-lock.
COPYRIGHT Kernel Hackers Manual 2.6. July 2010 BLK_MAKE_REQUEST(9)
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