__bread(9) [centos man page]

__BREAD(9)							   The Linux VFS							__BREAD(9)

NAME

       __bread - reads a specified block and returns the bh

SYNOPSIS

       struct buffer_head * __bread(struct block_device * bdev, sector_t block, unsigned size);

ARGUMENTS

       bdev
	   the block_device to read from

       block
	   number of block

       size
	   size (in bytes) to read

DESCRIPTION

       Reads a specified block, and returns buffer head that contains it. It returns NULL if the block was unreadable.

COPYRIGHT

Kernel Hackers Manual 3.10					     June 2014								__BREAD(9)

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

NAME

       probe::ioblock_trace.bounce - Fires whenever a buffer bounce is needed for at least one page of a block IO request.

SYNOPSIS

       ioblock_trace.bounce

VALUES

       None

DESCRIPTION

       name - name of the probe point q - request queue on which this bio was queued.  devname - device for which a buffer bounce was needed.  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 creating a block IO request.

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