LL_RW_BLOCK(9) The Linux VFS LL_RW_BLOCK(9)NAME
ll_rw_block - level access to block devices (DEPRECATED)
void ll_rw_block(int rw, int nr, struct buffer_head * bhs);
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 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 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
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 3.10 June 2014 LL_RW_BLOCK(9)
Check Out this Related Man Page
JOURNAL_GET_UNDO_ACC(9) The Linux Journalling API JOURNAL_GET_UNDO_ACC(9)NAME
journal_get_undo_access - Notify intent to modify metadata with non-rewindable consequences
int journal_get_undo_access(handle_t * handle, struct buffer_head * bh);
buffer to undo
Sometimes there is a need to distinguish between metadata which has been committed to disk and that which has not. The ext3fs code uses
this for freeing and allocating space, we have to make sure that we do not reuse freed space until the deallocation has been committed,
since if we overwrote that space we would make the delete un-rewindable in case of a crash.
To deal with that, journal_get_undo_access requests write access to a buffer for parts of non-rewindable operations such as delete
operations on the bitmaps. The journaling code must keep a copy of the buffer's contents prior to the undo_access call until such time as
we know that the buffer has definitely been committed to disk.
We never need to know which transaction the committed data is part of, buffers touched here are guaranteed to be dirtied later and so will
be committed to a new transaction in due course, at which point we can discard the old committed data pointer.
Returns error number or 0 on success.
Roger Gammans <firstname.lastname@example.org>
Stephen Tweedie <email@example.com>
COPYRIGHT Kernel Hackers Manual 2.6. July 2010 JOURNAL_GET_UNDO_ACC(9)
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