writeback: factor writeback_get_batch() out of write_cache_pages()

This simple helper will be the basis of the writeback iterator.  To make
this work, we need to remember the current index and end positions in
writeback_control.

[[email protected]: heavily rebased, add helpers to get the tag and end index, don't keep the end index in struct writeback_control]
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Matthew Wilcox (Oracle) <[email protected]>
Signed-off-by: Christoph Hellwig <[email protected]>
Reviewed-by: Brian Foster <[email protected]>
Reviewed-by: Jan Kara <[email protected]>
Acked-by: Dave Chinner <[email protected]>
Cc: Christian Brauner <[email protected]>
Cc: David Howells <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

0 files changed, 0 insertions, 0 deletions