__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)

LL_RW_BLOCK(9)							   The Linux VFS						    LL_RW_BLOCK(9)

NAME

       ll_rw_block - level access to block devices (DEPRECATED)

SYNOPSIS

       void ll_rw_block(int rw, int nr, struct buffer_head * bhs[]);

ARGUMENTS

       rw
	   whether to READ or WRITE or SWRITE or maybe READA (readahead)

       nr
	   number of struct buffer_heads in the array

       bhs[]
	   array of pointers to struct buffer_head

DESCRIPTION

       ll_rw_block takes an array of pointers to struct buffer_heads, and requests an I/O operation on them, either a READ or a WRITE. The third
       SWRITE is like WRITE only we make sure that the *current* data in buffers are sent to disk. The fourth READA option is described in the
       documentation for generic_make_request which ll_rw_block calls.

       This function drops any buffer that it cannot get a lock on (with the BH_Lock state bit) unless SWRITE is required, any buffer that appears
       to be clean when doing a write request, and any buffer that appears to be up-to-date when doing read request. Further it marks as clean
       buffers that are processed for writing (the buffer cache won't assume that they are actually clean until the buffer gets unlocked).

       ll_rw_block sets b_end_io to simple completion handler that marks the buffer up-to-date (if approriate), unlocks the buffer and wakes any
       waiters.

       All of the buffers must be for the same device, and must also be a multiple of the current approved size for the device.

COPYRIGHT

Kernel Hackers Manual 2.6.					     July 2010							    LL_RW_BLOCK(9)