On Sun, Aug 30, 2009 at 03:17:19PM -0500, James Bottomley wrote: > > > Jens had some objections to the block layer bits last time I posted > > > these. I forget what they were now (this would have been around May > > > 2nd, I think). What I've done instead in my current patchset (which > > > undoubtedly has bugs because it isn't tested, because I'm not supposed > > > to be working on the weekends) is to make sd_prep_fn() call a new method > > > in the scsi_host_template. That should translate the discard request > > > into a BLOCK_PC ATA_16 command, and we'll all be happy. > > > > > > It goes a little something like this: > > > http://git.kernel.org/?p=linux/kernel/git/willy/ssd.git;a=shortlog;h=trim-20090829 > > > > Queue flag and handling the discard in the prep function is much better > > than the prepare function, yes. I don't like the prep_fn callout to the > > host a lot. > > Me neither. I'm sort of OK with a transformed operation, callout for > the ULD, but I really don't see why a disk only function should go > through the host template. I'm fine with putting the function pointer elsewhere ... the host template seemed like a good place because the two things I see it being useful for (USB and ATA) are a per-host thing rather than a per-device thing. Would you like to see it in the scsi_disk instead? Maybe the scsi_device? > So the last ATA data set management with TRIM proposal I saw had a set > of discontiguous ranges, very like UNMAP. It's certainly possible to do > the transformation, you just have to drop the sector buffer and add one > for the ranges (then reverse it in the back translation for the > completion) but it's not pretty. Not pretty, and also has some practical problems, in that I cannot figure out where Linux stores the length. Even after I put on a new page, it would only send the first 24 bytes (length of the UNMAP payload) rather than the 512 bytes of the TRIM payload. -- Matthew Wilcox Intel Open Source Technology Centre "Bill, look, we understand that you're interested in selling us this operating system, but compare it to ours. We can't possibly take such a retrograde step." -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
