On Wed, Mar 16 2005, [EMAIL PROTECTED] wrote: > Jens Axboe wrote: > > On Wed, Mar 16 2005, [EMAIL PROTECTED] wrote: > >> Hayes, Stuart wrote: > >>> This patch will map the sg buffers to kernel virtual memory space in > >>> the functions idescsi_input_buffers() and idescsi_output_buffers(). > >>> Without this patch, idescsi passes a null pointer to > >>> atapi_input_bytes() and atapi_output_bytes() when sg pages are in > >>> high memory (i686 architecture). > >>> > >>> I'm attaching as a file, too, as the text will certainly be wrapped. > >>> > >>> (Sorry for the subject rename--I'm trying to use the correct format > >>> for patch emails.) > >>> > >>> Thanks > >>> Stuart > >> > >> And, while there's another high memory/kmap patch question on this > >> list... > >> > >> Is there some reason nobody seems interested in this patch (except > >> Jens--thanks for the help!)? I'm kind of new to sending in patches, > >> and I'm not sure if I'm just not waiting long enough, or if there is > >> a problem with this patch... > >> > >> But really, we're getting a null pointer dereference oops when using > >> ATAPI tape drives (with ide-scsi) without this patch... > > > > Sorry, that did seem to get dropped on the floor. Actually I'm > > wondering why you are seeing highmem pages there in the first place, > > it would be easier/better just to limit ide-scsi to non-highmem > > pages. That would remove the need to add any work arounds in the > > driver. > > I think we're seeing highmem pages in the sg list because that's where > the user memory was when st_write() was called. > > The sg list is set up when st_write(), which calls setup_buffering(), > which calls st_map_user_pages()... this just sets up the sg pages to > point directly to the user memory. So, by the time ide-scsi comes into > the picture, the sg list is already set up to point to high memory > pages. > > Are you suggesting that ide-scsi should change the dma_mask for the > device so that st_map_user_pages() won't let sg pages point to high > memory? Or is there something else I'm missing?
I think that is a bug, this effectively bypasses whatever restrictions the scsi host adapter has said about memory limits. It is a problem because the request doesn't come from the block layer (which handles all of this). I would much prefer fixing that real issue! -- Jens Axboe - To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
