Merge tag 'mmc-v4.3-rc3' of git://git.linaro.org/people/ulf.hansson/mmc

[karo-tx-linux.git] / mm / filemap.c

diff --git a/mm/filemap.c b/mm/filemap.c
index 1283fc82545861d155c4eef7013bf8e285040fed..72940fb38666811b80c146bc085a1c84fc0e7ecc 100644 (file)
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -674,7 +674,7 @@ struct page *__page_cache_alloc(gfp_t gfp)
                do {
                        cpuset_mems_cookie = read_mems_allowed_begin();
                        n = cpuset_mem_spread_node();
-                       page = alloc_pages_exact_node(n, gfp, 0);
+                       page = __alloc_pages_node(n, gfp, 0);
                } while (!page && read_mems_allowed_retry(cpuset_mems_cookie));
 
                return page;
@@ -2473,21 +2473,6 @@ ssize_t generic_perform_write(struct file *file,
                                                iov_iter_count(i));
 
 again:
-               /*
-                * Bring in the user page that we will copy from _first_.
-                * Otherwise there's a nasty deadlock on copying from the
-                * same page as we're writing to, without it being marked
-                * up-to-date.
-                *
-                * Not only is this an optimisation, but it is also required
-                * to check that the address is actually valid, when atomic
-                * usercopies are used, below.
-                */
-               if (unlikely(iov_iter_fault_in_readable(i, bytes))) {
-                       status = -EFAULT;
-                       break;
-               }
-
                status = a_ops->write_begin(file, mapping, pos, bytes, flags,
                                                &page, &fsdata);
                if (unlikely(status < 0))
@@ -2495,8 +2480,17 @@ again:
 
                if (mapping_writably_mapped(mapping))
                        flush_dcache_page(page);
-
+               /*
+                * 'page' is now locked.  If we are trying to copy from a
+                * mapping of 'page' in userspace, the copy might fault and
+                * would need PageUptodate() to complete.  But, page can not be
+                * made Uptodate without acquiring the page lock, which we hold.
+                * Deadlock.  Avoid with pagefault_disable().  Fix up below with
+                * iov_iter_fault_in_readable().
+                */
+               pagefault_disable();
                copied = iov_iter_copy_from_user_atomic(page, i, offset, bytes);
+               pagefault_enable();
                flush_dcache_page(page);
 
                status = a_ops->write_end(file, mapping, pos, bytes, copied,
@@ -2519,6 +2513,14 @@ again:
                         */
                        bytes = min_t(unsigned long, PAGE_CACHE_SIZE - offset,
                                                iov_iter_single_seg_count(i));
+                       /*
+                        * This is the fallback to recover if the copy from
+                        * userspace above faults.
+                        */
+                       if (unlikely(iov_iter_fault_in_readable(i, bytes))) {
+                               status = -EFAULT;
+                               break;
+                       }
                        goto again;
                }
                pos += copied;