On Sunday 14 October 2007 12:46:12 pm Stefan Richter wrote: > David Newall wrote: > > That is so rude. When a reply contains as a reply to the first paragraph "you're wrong" with no elaboration, and as a reply to the second paragraph nothing but expletives and personal insults, I tend to stop reading. It really doesn't come across as a serious reply. I was at least attempting to ask a serious question. > Such responses sometimes happen after provocative posts like the thread > starter's. He could have asked straight away for help with fixing his > boot environment instead of wrapping his question into a feigned design > discussion. It appeared as if he is out for a fight rather than > interested in help. Actually, I was going through Documentation/block thinking about making a 00-INDEX for it, but my earlier questions of the scsi guys left me with the impression that the block layer is _not_ used by the SCSI layer. And since every non-embedded modern storage device I'm aware of has been consumed by the SCSI layer (despite none of them actually having a discernably closer relationship to SCSI than ATA did), I didn't know whether or not it was more appropriate to index this directory or request its deletion. So I asked. Back when I asked the scsi guys about this, I got no direct answer. I asked "where does the block layer work into this" in the context of questiosn about the relationship between the scsi upper, middle, and lower layers, and I never got a reply, even though the question was quoted back at me here: http://www.mail-archive.com/linux-scsi%40vger.kernel.org/msg09086.html The closest I got to an answer was later in the thread: http://www.mail-archive.com/linux-scsi%40vger.kernel.org/msg09131.html Which said: > That approach makes the Linux block layer either a nuisance, > irrelevant or a complete anachronism (in the case of OSD). > IMO the linux block layer should be morphed into a library > of internal queue handling routines. Storage upper level > drivers such as sd can continue to present the "block" > view ** of storage devices such as disks. The gist of the thread (and the documentation I was referred to) is that the scsi "upper layer" presents /dev nodes and ioctls, the scsi mid-layer is a routing layer very roughly analogus to a TCP/IP stack, and the scsi low-layer drivers interface with specific pieces of hardware. Apparently, the block layer is not between any of these, they talk directly to each other. This would seem to indicate that I/O requests made to scsi devices are never routed through a common block I/O request handling layer shared with non-SCSI block devices. I was not, however, certain of this, hence my attempt to bring the topic back up. Oh, and sending a patch correcting Jens Axboe's address in this old documentation. He's apparently at Oracle now... Rob -- "One of my most productive days was throwing away 1000 lines of code." - Ken Thompson. - 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
