On Fri, Feb 29 2008, James Bottomley wrote: > > On Fri, 2008-02-29 at 00:46 +0900, Tejun Heo wrote: > > Jens Axboe wrote: > > >> This problem was reported and diagnosed by Mike Galbraith. > > > > > > Tejun, this patch isn't much cleaner at all. It really shows the pain of > > > these two seperate, yet related, variables. > > > > Not much cleaner compared to what? I think padding stuff is bound to be > > somewhat complex. It's a nasty thing in nature. I think ->extra_len is > > better than ->raw_data_len because ->extra_len only needs to be updated > > where the dirty jobs are done and extra buffer areas are added. Any > > better suggestions? > > Well, I just investigated a bug report in the SCSI transport class. Our > SMP handler is broken in exactly the same way. We rely on the incoming > reported request lengths to size our request data, and they've blown up > from the true length to 512 bytes (the size of our alignment). > > With the original patch, I have to run through the whole of libsas and > scsi_transport_sas doing > > s/data_len/raw_data_len/ > > With your update it looks like I have to run through them all doing > > s/data_len/data_len - extra_len/ > > which is even worse. Can't we put things back to a point where data_len > means exactly that and extra_len means how much we have spare on the > end, so you know you can DMA up to data_len + extra_len if need be? > > That way we don't have to sweep through every block driver altering the > way it uses data_len. Fully agree. The reason why I think it's so ugly is that you have to keep these two seperate variables in sync. The burning was just one bug, there will be others... -- Jens Axboe -- 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
