>>>>> "Allison" == Allison Henderson <achender@xxxxxxxxxxxxxxxxxx> writes: >> Does sb_issue_zeroout() use the SCSI "write same" feature in the >> background? That would avoid busying the CPU/controller/bus with >> writing out zeroes, which might be expensive for a large file. >> Allison> Hmm, that's a good question, I will dig into it and see if I Allison> can find out. This is a bit of an ongoing project. Unfortunately WRITE SAME is quirk central as many drives only implement block ranges corresponding to what RAID vendors told them they needed. Many of the drives I tested have internal caps at 16 or 32MB and will fail in interesting (i.e. not necessarily graceful) ways if given bigger ranges. I've been lobbying for a way for devices to report their WRITE SAME limit for a while. That feature finally made it into the latest SBC3 draft. The changes required to support it went into the SCSI layer during the last merge window. What remains is wiring this up to blkdev_issue_zeroout(). I have some patches sitting in my queue that I hope to get polished and submitted soon. Anyway. From a filesystem perspective sb_issue_zeroout() interface is definitely the way to go. WRITE SAME will eventually be called if the device supports it. -- Martin K. Petersen Oracle Linux Engineering -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
