On Sun, Apr 29, 2012 at 02:03:41PM -0700, Alexandre Depoutovitch wrote: > + if (current->mm) { > + ret = get_user_pages_fast( > + dio->curr_user_address, /* Where from? */ > + nr_pages, /* How many pages? */ > + dio->rw == READ, /* Write to memory? */ > + &dio->pages[0]); /* Put results here */ > + } else { > + /* For kernel threads mm is NULL, so all we need is to increment > + page's reference count and add page to dio->pages array */ > + int i; > + struct page* page; > + unsigned long start_pfn = virt_to_phys((void > *)dio->curr_user_address) > + >> PAGE_SHIFT; > + /* For kernel threads buffer must be in kernel memory */ > + BUG_ON(dio->curr_user_address < TASK_SIZE_MAX); This is an assumption that isn't true for all architectures. Better just delete this line. > + for (i = 0; i < nr_pages; i++) { > + page = pfn_to_page(start_pfn + i); Why are you messing about with pfns? Why not just stay with virtual addresses and call virt_to_page() in this loop? That would ensure that this works to vmapped pages as well as physically contiguous pages. > + page_cache_get(page); > + dio->pages[i] = page; > + } > + /* No need to lock pages: this is kernel thread and the pages are in > + kernel as well */ > + ret = nr_pages; > + } > > if (ret < 0 && dio->blocks_available && (dio->rw & WRITE)) { > struct page *page = ZERO_PAGE(0); > @@ -972,7 +991,11 @@ > break; > } > > - /* Drop the ref which was taken in get_user_pages() */ > + /* > + * Drop the ref which was taken in dio_refill_pages > + * directly (for direct I/O) or by calling get_user_pages > + * (for buffered IO) > + */ I think your change to this comment actually makes it more confusing. > @@ -1348,6 +1351,58 @@ > nfsd_max_blksize); > } > > +int nfsd_directio_mode = DIO_NEVER; > + > +/** > + * nfsd_directio_mode - sets conditions when direct IO is activated > + * > + * Input: > + * buf: ignored > + * size: zero > + * > + * OR > + * > + * Input: > + * buf: C string containing an unsigned > + * integer value representing the new > + * NFS direct IO mode > + * size: non-zero length of C string in @buf > + * Output: > + * On success: passed-in buffer filled with '\n'-terminated C string > + * containing numeric value of the current direct IO mode > + * return code is the size in bytes of the string > + * > + * Possible modes are: > + * DIO_NEVER (0) - never use direct I/O > + * DIO_FS_UNALIGNED (1) - use direct I/O only for requests that FS > unaligned > + * and block device aligned > + * DIO_SECTOR_ALIGNED (3) - use direct I/O for all block device aligned > IO > + * On error: return code is zero or a negative errno value > + */ This is not correct kerneldoc formatting. -- Matthew Wilcox Intel Open Source Technology Centre "Bill, look, we understand that you're interested in selling us this operating system, but compare it to ours. We can't possibly take such a retrograde step." -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html