Hi Doug, Forgot to report this. I've tested your patch and it works. Thanks, Fajun On 8/18/06, Douglas Gilbert <dougg@xxxxxxxxxx> wrote:
Douglas Gilbert wrote: > Fajun Chen wrote: >> Hi Folks, >> >> I use ATA pass through via sg ioctl interface for data read/write. >> Linux 2.6.18-rc2 patched with Jeff Garzik's libata git patch was >> running on ARM IOP80321 board. The HBA Sil3124 was used. >> >> Two problems were observed: >> 1. sg mmap bug? >> My test program could not write data correctly to the mmapped >> buffer in the user space. The program did a read immediately >> after a write and the data mismatches. Swapped the sg_vma_nopage() >> function with the one in 2.6.15.4 release fixed the problem. So this >> appears to be a wrong change to the sg mmap code in 2.6.18-rc2 >> release. > > Thanks for the report. I can confirm that mmap-ed IO > in the sg driver is broken. Simply reading 16 blocks > from some arbitrary offset with sg_dd and sgm_dd > and comparing the fetched data shows mismatches starting > above the first page (i.e. above byte offset 4096 on > i386). > > Your point about the change to sg_vma_nopage() between > lk 2.6.15 and lk 2.6.16 also seems to be correct. > The most indented part of that function has been > changed from incrementing the change count on the > reported page (as indicated by 'offset') in a > compound page allocation to ignoring the 'offset' > and incrementing the page count on the first page > in a compound page allocation. Fajun, Could you please try the patch below and report if it fixes your sg mmap problem. The patch is against lk 2.6.18-rc4 and I assume it will apply against "rc2" as well. The patch re-instates the former logic and fixes the problem in my tests. Doug Gilbert
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