squashfs: implement readahead

Implement readahead callback for squashfs.  It will read datablocks which
cover pages in readahead request.  For a few cases it will not mark page
as uptodate, including:

- file end is 0.
- zero filled blocks.
- current batch of pages isn't in the same datablock.
- decompressor error.

Otherwise pages will be marked as uptodate.  The unhandled pages will be
updated by readpage later.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Hsin-Yi Wang <[email protected]>
Suggested-by: Matthew Wilcox <[email protected]>
Reported-by: Matthew Wilcox <[email protected]>
Reported-by: Phillip Lougher <[email protected]>
Reported-by: Xiongwei Song <[email protected]>
Reported-by: Andrew Morton <[email protected]>
Cc: Hou Tao <[email protected]>
Cc: kernel test robot <[email protected]>
Cc: Marek Szyprowski <[email protected]>
Cc: Miao Xie <[email protected]>
Cc: Zhang Yi <[email protected]>
Cc: Zheng Liang <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

0 files changed, 0 insertions, 0 deletions