On 2020/03/25 18:48, hch@xxxxxxxxxxxxx wrote: > On Wed, Mar 25, 2020 at 09:45:39AM +0000, Johannes Thumshirn wrote: >> >> Can you please elaborate on that? Why doesn't this hold true for a >> normal file system? If we split the DIO write into multiple BIOs with >> zone-append, there is nothing which guarantees the order of the written >> data (at least as far as I can see). > > Of course nothing gurantees the order. But the whole point is that the > order does not matter. > The order does not matter at the DIO level since iomap dio end callback will allow the FS to add an extent mapping the written data using the drive indicated write location. But that callback is for the entire DIO, not per BIO fragment of the DIO. So if the BIO fragments of a large DIO get reordered, as Johannes said, we will get data corruption in the FS extent. No ? -- Damien Le Moal Western Digital Research
