On 24/03/2020 16:41, Christoph Hellwig wrote: >> + >> + /* >> + * Issuing multiple BIOs for a large zone append write can >> + * result in reordering of the write fragments and to data >> + * corruption. So always stop after the first BIO is issued. >> + */ >> + if (zone_append) >> + break; > At least for a normal file system that is absolutely not true. If > zonefs is so special it might be better of just using a slightly tweaked > copy of blkdev_direct_IO rather than using iomap. > 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). So if we have this DIO write: |AAAAA|BBBB|CCCC|DDDD| and we have to split it for whatever reason, what safe guards us from it ending up on disk like this: |CCCC|DDDD|AAAA|BBBB| This is essentially the same reason we can't split zone-append BIOs, or am I totally off track now? Thanks, Johannes
