On 2022/08/10 1:33, John Garry wrote: > On 09/08/2022 15:57, Damien Le Moal wrote: >>>> As far as I can see, this patch should not make a difference unless the >>>> ATA shost driver is setting the max_sectors value unnecessarily low. >>> For __ATA_BASE_SHT, we don't set max_sectors. As such, we default >>> shost->max_sectors = SCSI_DEFAULT_MAX_SECTORS (=1024) in >>> scsi_host_alloc(). I assume no shost dma mapping limit applied. >>> >>> Then - for example - we could select dev->max_sectors = >>> ATA_MAX_SECTORS_LBA48 (=65535) in ata_dev_configure(). >>> >>> So with commit 0568e6122574 we would have final max sectors = 1024, as >>> opposed to 65535 previously. I guess that the problem is something like >>> this. >>> >>> If so, it seems that we would need to apply the shost dma mapping limit >>> separately in ata_scsi_dev_config() and not use shost->max_sectors. >> OK. Will have a look at that. >> > > We may need to introduce something like shost->max_hw_sectors, which is > set according to sht max sectors and dma mapping limits. That could be > also used in USB scsiglue slave_configure() > > Or else set max_sectors value for __ATA_BASE_SHT, but I don't know a > sane value there considering ATA_MAX_SECTORS_LBA48 gives max_sectors of > 65535. > > Damien, please let me know if you need help now. I am just waiting for > you to test to prove this theory about dev->max_sectors being capped. I > don't have an AHCI setup readily-available for testing - just SAS cards > or QEMU. I am on it. > > Thanks, > John -- Damien Le Moal Western Digital Research
