__get_request(9) [centos man page]

__GET_REQUEST(9)						   Block Devices						  __GET_REQUEST(9)

NAME

       __get_request - get a free request

SYNOPSIS

       struct request * __get_request(struct request_list * rl, int rw_flags, struct bio * bio, gfp_t gfp_mask);

ARGUMENTS

       rl
	   request list to allocate from

       rw_flags
	   RW and SYNC flags

       bio
	   bio to allocate request for (can be NULL)

       gfp_mask
	   allocation mask

DESCRIPTION

       Get a free request from q. This function may fail under memory pressure or if q is dead.

       Must be callled with q->queue_lock held and, Returns NULL on failure, with q->queue_lock held. Returns !NULL on success, with q->queue_lock
       *not held*.

COPYRIGHT

Kernel Hackers Manual 3.10					     June 2014							  __GET_REQUEST(9)

PROBE::IOBLOCK_TRACE(3stap)				  IO Scheduler and block IO Taps			       PROBE::IOBLOCK_TRACE(3stap)

NAME

       probe::ioblock_trace.request - Fires just as a generic block I/O request is created for a bio.

SYNOPSIS

       ioblock_trace.request

VALUES

       None

DESCRIPTION

       name - name of the probe point q - request queue on which this bio was queued.  devname - block device name ino - i-node number of the
       mapped file bytes_done - number of bytes transferred sector - beginning sector for the entire bio flags - see below BIO_UPTODATE 0 ok after
       I/O completion BIO_RW_BLOCK 1 RW_AHEAD set, and read/write would block BIO_EOF 2 out-out-bounds error BIO_SEG_VALID 3 nr_hw_seg valid
       BIO_CLONED 4 doesn't own data BIO_BOUNCED 5 bio is a bounce bio BIO_USER_MAPPED 6 contains user pages BIO_EOPNOTSUPP 7 not supported

       rw - binary trace for read/write request vcnt - bio vector count which represents number of array element (page, offset, length) which make
       up this I/O request idx - offset into the bio vector array phys_segments - number of segments in this bio after physical address coalescing
       is performed.  size - total size in bytes bdev - target block device bdev_contains - points to the device object which contains the
       partition (when bio structure represents a partition) p_start_sect - points to the start sector of the partition structure of the device

CONTEXT

       The process makes block I/O request

SystemTap Tapset Reference					     June 2014					       PROBE::IOBLOCK_TRACE(3stap)