[PATCH 1/9] readahead: simplify readahead call scheme

It is insane and error-prone to insist on the call sites to check for async readahead after doing any sync one. I.e. whenever someone do a sync readahead: if (!page) page_cache_sync_readahead(...); He must try async readahead

[PATCH 1/9] readahead: simplify readahead call scheme

It is insane and error-prone to insist on the call sites to check for async readahead after doing any sync one. I.e. whenever someone do a sync readahead: if (!page) page_cache_sync_readahead(...); He must try async readahead