readahead: drop dead code in ondemand_readahead()

ondemand_readahead() scales up the readahead window if the current read
would hit the readahead mark placed by itself.  However the condition is
mostly dead code because:

a) In case of async readahead we always increase ra->start so ra->start
   == index is never true.

b) In case of sync readahead we either go through
   try_context_readahead() in which case ra->async_size == 1 < ra->size or
   we go through initial_readahead where ra->async_size == ra->size iff
   ra->size == max_pages.

So the only practical effect is reducing async_size for large initial
reads.  Make the code more obvious.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Jan Kara <[email protected]>
Reviewed-by: Josef Bacik <[email protected]>
Tested-by: Zhang Peng <[email protected]>
Cc: Matthew Wilcox (Oracle) <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

0 files changed, 0 insertions, 0 deletions