[PATCH 0/4] use write_cache_pages

[Christoph Hellwig <hch@xxxxxxxxxxxxx>]

Replace our own handcrafted I/O clustering with the generic write_cache_pages
helper.  While the old code would add any additional page in an existing
mapping, the new code iterates over the pages, either adding them to
a previous mapping if it fits or otherwise gets a new one.

This has survived xfsqa for small and 4k blocksize on x86.