The Linux Kernel API | ||
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whether to READ
or WRITE
or maybe READA
(readahead)
number of &struct buffer_heads in the array
array of pointers to &struct buffer_head
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 READA
option is described in the documentation for
generic_make_request which ll_rw_block calls.
This function provides extra functionality that is not in generic_make_request that is relevant to buffers in the buffer cache or page cache. In particular it drops any buffer that it cannot get a lock on (with the BH_Lock state bit), 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 wont 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. As client that needs a more interesting completion routine should call submit_bh (or generic_make_request) directly.
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