Hi list, I'm writing a SCSI LLD in which i have a requirement to copy the SCSI mid-layer supplied request_buffer(as a SG list) in the Scsi_Cmnd structure to a local buffer in the LLD. Hence i need the virtual address of the mapped SGs but attempt to mapping results in a panic. Configuration: i386 SMP machine with 1GB RAM under kernel 2.6.11.8 or 2.6.9.x(RHEL4) I get a kernel panic under the below mentioned condition: 1) parse thro' the mid layer supplied SG list elements 2) do a kmap_atomic() (the code is in interrupt context) on the page and get a virtual addr(vaddr) 3) memcpy the returned vaddr into local buffer upto the length of the SG element received in the scatterlist 4) kunmap_atomic the virtual addr This works fine as long as the SG element page size is <4K and is in lowmem area. If the SG element page is in highmem(PG_Highmem is set in page->flags) and the SG length is >4k (say 8k) then the memcpy panics at the address vaddr+4K. Apparently kmap_atomic mapped only the first 4K of the 8K page properly and hence the start of the panic happened at the start of next 4K. My questions here are: 1) how to find the address of the next 'page' structure if the SG element specifies a length of 8k since PAGE_SIZE is 4k on i386 2) is there an alternative to map page to virtual address safely under interrupt context Please correct me if I'm missing something here. Any help is thankfully appreciated. thanks, naveen PS: I'm not subscribed to this list, please CC me on replies. - : 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
