On 11/28/18 3:35 PM, Christoph Hellwig wrote: > On Wed, Nov 28, 2018 at 04:08:50PM +1100, Dave Chinner wrote: >> So the first time through this loop the block layer devices what >> device to read from, then we iterate devices 1..n on error. >> >> Whihc means if device 0 is the only one with good information in it, >> we may not ever actually read from it. >> >> I'd suggest that a hint of "-1" (or equivalent max value) should be >> used for "device selects mirror leg" rather than 0, so we can >> actually read from the first device on command. > > Yes. For one thing I think we really need to split this retry counter > of sorts from the write hints. I.e. make both u8 types and keep them > separate. Then start out with (u8)-1 as initialized by the block layer > for the first attempt. The device then fills out which leg it used > (in the completion path, so that another underlying driver doesn't > override it!), and then the file system just preserves this value on > a resumit, leaving the driver to chose a new value when it gets a > non -1 value. > Will update as suggested, thank you for all your feedback :) -Bob
