Further to the problem discussed in this post: http://marc.theaimsgroup.com/?l=linux-scsi&m=112540053711489&w=2 It seems that the sg driver does not need to set the VM_IO flag on pages that it memory maps to the user space since they are not from the IO space. Ahmed Teirelbar <ahmed.teirelbar@xxxxxxxx> wants the facility and has tested this patch as I have without adverse effects. Patch is against lk 2.6.13 with this "[PATCH] sg direct io/mmap oops, st sync" applied. The oops protection is still important. Some users really did try and use dio transfers from the sg driver to memory mapped IO space (on a video capture card if my memory serves) during the lk 2.4 series. I'm not sure how successful it was but that will now be politely refused in lk 2.6.13+ . Changelog: - set the page flags for sg's reserved buffer mmap-ed to the user space to VM_RESERVED (rather than VM_RESERVED | VM_IO ) Signed-off-by: Douglas Gilbert <dougg@xxxxxxxxxx> Doug Gilbert
--- linux/drivers/scsi/sg.c 2005-09-01 21:30:39.000000000 +1000 +++ linux/drivers/scsi/sg.c2613kai_vmio 2005-09-08 20:36:39.000000000 +1000 @@ -61,7 +61,7 @@ #ifdef CONFIG_SCSI_PROC_FS #include <linux/proc_fs.h> -static char *sg_version_date = "20050901"; +static char *sg_version_date = "20050908"; static int sg_proc_init(void); static void sg_proc_cleanup(void); @@ -1300,7 +1300,7 @@ sg_rb_correct4mmap(rsv_schp, 1); /* do only once per fd lifetime */ sfp->mmap_called = 1; } - vma->vm_flags |= (VM_RESERVED | VM_IO); + vma->vm_flags |= VM_RESERVED; vma->vm_private_data = sfp; vma->vm_ops = &sg_mmap_vm_ops; return 0;
