On Thu, May 24, 2018 at 10:02:51AM -0600, Jens Axboe wrote: > The only caller of ->readpages() is from read-ahead, yet we don't > submit IO flagged with REQ_RAHEAD. This means we don't see it in > blktrace, for instance, which is a shame. We already make assumptions > about ->readpages() just being for read-ahead in the mpage > implementation, using readahead_gfp_mask(mapping) as out GFP mask of > choice. > > This small series fixes up mpage_readpages() to submit with > REQ_RAHEAD, which takes care of file systems using mpage_readpages(). > The last two fixup ext4 and btrfs. What are the benefits? Any setup where this buys us anything? Any setup where this actually regressed because drivers/hardware are doing stupid things with REQ_RAHEAD?
