1 files changed, 16 insertions, 22 deletions

diff --git a/mm/filemap.c b/mm/filemap.c
index 66f7e9fdfbc4..d1458ecf2f51 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -872,7 +872,7 @@ noinline int __add_to_page_cache_locked(struct page *page,
 	page->index = offset;
 
 	if (!huge) {
-		error = mem_cgroup_charge(page, current->mm, gfp);
+		error = mem_cgroup_charge(page, NULL, gfp);
 		if (error)
 			goto error;
 		charged = true;
@@ -3642,10 +3642,6 @@ again:
 		 * 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;
@@ -3665,33 +3661,31 @@ again:
 		if (mapping_writably_mapped(mapping))
 			flush_dcache_page(page);
 
-		copied = iov_iter_copy_from_user_atomic(page, i, offset, bytes);
+		copied = copy_page_from_iter_atomic(page, offset, bytes, i);
 		flush_dcache_page(page);
 
 		status = a_ops->write_end(file, mapping, pos, bytes, copied,
 						page, fsdata);
-		if (unlikely(status < 0))
-			break;
-		copied = status;
-
+		if (unlikely(status != copied)) {
+			iov_iter_revert(i, copied - max(status, 0L));
+			if (unlikely(status < 0))
+				break;
+		}
 		cond_resched();
 
-		iov_iter_advance(i, copied);
-		if (unlikely(copied == 0)) {
+		if (unlikely(status == 0)) {
 			/*
-			 * If we were unable to copy any data at all, we must
-			 * fall back to a single segment length write.
-			 *
-			 * If we didn't fallback here, we could livelock
-			 * because not all segments in the iov can be copied at
-			 * once without a pagefault.
+			 * A short copy made ->write_end() reject the
+			 * thing entirely.  Might be memory poisoning
+			 * halfway through, might be a race with munmap,
+			 * might be severe memory pressure.
 			 */
-			bytes = min_t(unsigned long, PAGE_SIZE - offset,
-						iov_iter_single_seg_count(i));
+			if (copied)
+				bytes = copied;
 			goto again;
 		}
-		pos += copied;
-		written += copied;
+		pos += status;
+		written += status;
 
 		balance_dirty_pages_ratelimited(mapping);
 	} while (iov_iter_count(i));