Rusty Russell wrote: > On Monday 07 January 2008 16:01:40 Tejun Heo wrote: >>> But we hit the same problems: >>> >>> 1) sg_chain loses information. The clever chain packaging makes reading >>> easy, but manipulation is severely limited. You can append to your own >>> chains by padding, but not someone elses. This works for SCSI, but what >>> about the rest of us? And don't even think of joining mapped chains: it >>> will almost work. >> You can append by allocating one more element on the chain to be >> appended and moving the last element of the first chain to it while >> using the last element for chaining. > > Hi Tejun, > > Nice try! Even ignoring the ugliness of undoing such an operation if the > caller doesn't expect you to mangle their chains, consider a one-element sg > array. :( Heh heh, that can be dealt with by skipping the first chain if the first chain is empty after chaining. Please take a look at ata_sg_setup_extra() in the following. http://git.kernel.org/?p=linux/kernel/git/tj/libata-dev.git;a=blob;f=drivers/ata/libata-core.c;h=32dde5bbc75ed53e89ac17040da2cd0621a37161;hb=c8847e473a4a2844244784226eb362be10d52ce9 That said, yeah, it's seriously ugly. Restoring the original sg is ugly too. I definitely agree that we need some improvements here. -- tejun - 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
