On Wed, 17 Dec 2008 22:56:47 +0200 (EET) Kai Makisara <Kai.Makisara@xxxxxxxxxxx> wrote: > On Wed, 17 Dec 2008, FUJITA Tomonori wrote: > > ... > > > However, one thing > > > puzzles me: today trying block size above 6144 kB returns EBUSY whereas > > > yesterday I could use 16000 kB (although with data corruption but this > > > should be fixed by your new patch that increments the offset between > > > bios)? > > > > Can you check where the error happened? > > > > If the error happened in ll_back_merge_fn via blk_rq_append_bio > > (EINVAL), it might be due to the following fix (which I put in the > > patch) : > > > > http://marc.info/?l=linux-scsi&m=122927795113939&w=2 > > > > This patch should do the right thing but this leads to more > > segments. But if your scsi host enables use_clustering, the error > > should not happen there. > > > > > > BTW, st driver in 2.6.27 can handle 16000 kB? > > > I tested 2.6.27.7 and it also maxed out at 6144 kB. The previous version > where I successfully tested this was 2.6.15. I remembered that I had to > tune some parameters to enable very large transfers. These are summarized > in http://marc.info/?l=linux-scsi&m=114147793010513&w=2 > > My SCSI HBA is sym53c1010. The driver limits number of s/g segments to 96. > Multiplying 64 kB * 96 = 6144 kB. This explains the limit. > > Next I added call > blk_queue_max_segment_size(sdev->request_queue, 256 * 1024); > to sym53c8xx_slave_configure(). Now I can read and write 16000 kB records. I see, thanks. > > > I will do some more tests tomorrow but your code looks really good. > > > I have done more tests and found only one minor problem. You patch fixes > the order in page frames. If one writes first smallish blocks (e.g., > label) and then large blocks, allocation may not reach the goal because > the order is too small. > > The patch at the end fixes this by retrying allocation from the beginning > if the order is too small. The patch also fixes two very old bugs. The > maximum order should have been 6. It enables maximum block size allowed by > WRITE(6) with 64 segments. The patch also makes enlarge_buffer() return > error if the maximum order together with maximum number of s/g segments. > > The patch applies on top of my previous patch removing > st_scsi_kern_execute(). Feel free to include these changes into one of > your own patches if you wish. Thanks a lot! I put both patches to the second version of the patchset. About the second patch, it might be cleaner to start with MAX_ORDER and decrease the order like osst? Anyway, it should be a different cleanup though. -- 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
