Visit Our UNIX and Linux User Community

Linux and UNIX Man Pages

Test Your Knowledge in Computers #951
Difficulty: Medium
The first known description of a self-reproducing computer program in science fiction was in a short story written in 1970.
True or False?
Linux & Unix Commands - Search Man Pages

blk_make_request(9) [centos man page]

BLK_MAKE_REQUEST(9)						   Block Devices					       BLK_MAKE_REQUEST(9)

NAME
blk_make_request - given a bio, allocate a corresponding struct request. SYNOPSIS
struct request * blk_make_request(struct request_queue * q, struct bio * bio, gfp_t gfp_mask); ARGUMENTS
q target request queue bio 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_mask gfp flags to be used for memory allocation DESCRIPTION
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. WARNING
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 3.10 June 2014 BLK_MAKE_REQUEST(9)

Check Out this Related Man Page

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

NAME
probe::ioblock_trace.end - Fires whenever a block I/O transfer is complete. SYNOPSIS
ioblock_trace.end 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 makes 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 signals the transfer is done. SystemTap Tapset Reference June 2014 PROBE::IOBLOCK_TRACE(3stap)

3 More Discussions You Might Find Interesting

1. UNIX for Dummies Questions & Answers

Save 43p bios?

Is there any way to backup the bios on a 43P-140 7043? (0 Replies)
Discussion started by: freestyle10269
0 Replies

2. UNIX Desktop Questions & Answers

Please Help me out with this question

. Make a new copy of mars.txt called marsx. What happens if you give the following commands when the files bio and marsx both already exist? Don't guess, try it! a) cp bio marsx b) mv bio marsx (2 Replies)
Discussion started by: rohit.katpalli
2 Replies

3. Hardware

qosmio f50-freeze when trying to update bios-black screen

Hi! I own a Qosmio f50 laptop and today i download the file from toshiba to update my bios. Everything went well until installer reaches block 16 when system freezes. I left it half an hour and then tried to power-off the pc with the button, but it dont. I unplug the ac-adaptor and the battery and... (0 Replies)
Discussion started by: giampoul
0 Replies

Featured Tech Videos