Merge branch 'work.iov_iter' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

Pull iov_iter updates from Al Viro:
 "iov_iter cleanups and fixes.

  There are followups, but this is what had sat in -next this cycle. IMO
  the macro forest in there became much thinner and easier to follow..."

* 'work.iov_iter' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (37 commits)
  csum_and_copy_to_pipe_iter(): leave handling of csum_state to caller
  clean up copy_mc_pipe_to_iter()
  pipe_zero(): we don't need no stinkin' kmap_atomic()...
  iov_iter: clean csum_and_copy_...() primitives up a bit
  copy_page_from_iter(): don't need kmap_atomic() for kvec/bvec cases
  copy_page_to_iter(): don't bother with kmap_atomic() for bvec/kvec cases
  iterate_xarray(): only of the first iteration we might get offset != 0
  pull handling of ->iov_offset into iterate_{iovec,bvec,xarray}
  iov_iter: make iterator callbacks use base and len instead of iovec
  iov_iter: make the amount already copied available to iterator callbacks
  iov_iter: get rid of separate bvec and xarray callbacks
  iov_iter: teach iterate_{bvec,xarray}() about possible short copies
  iterate_bvec(): expand bvec.h macro forest, massage a bit
  iov_iter: unify iterate_iovec and iterate_kvec
  iov_iter: massage iterate_iovec and iterate_kvec to logics similar to iterate_bvec
  iterate_and_advance(): get rid of magic in case when n is 0
  csum_and_copy_to_iter(): massage into form closer to csum_and_copy_from_iter()
  iov_iter: replace iov_iter_copy_from_user_atomic() with iterator-advancing variant
  [xarray] iov_iter_npages(): just use DIV_ROUND_UP()
  iov_iter_npages(): don't bother with iterate_all_kinds()
  ...

4 files changed, 37 insertions, 58 deletions

diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index 28a05ba47060..ee34497500e1 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -399,7 +399,7 @@ static noinline int btrfs_copy_from_user(loff_t pos, size_t write_bytes,
 		/*
 		 * Copy data from userspace to the current page
 		 */
-		copied = iov_iter_copy_from_user_atomic(page, i, offset, count);
+		copied = copy_page_from_iter_atomic(page, offset, count, i);
 
 		/* Flush processor's dcache for this page */
 		flush_dcache_page(page);
@@ -413,20 +413,19 @@ static noinline int btrfs_copy_from_user(loff_t pos, size_t write_bytes,
 		 * The rest of the btrfs_file_write code will fall
 		 * back to page at a time copies after we return 0.
 		 */
-		if (!PageUptodate(page) && copied < count)
-			copied = 0;
+		if (unlikely(copied < count)) {
+			if (!PageUptodate(page)) {
+				iov_iter_revert(i, copied);
+				copied = 0;
+			}
+			if (!copied)
+				break;
+		}
 
-		iov_iter_advance(i, copied);
 		write_bytes -= copied;
 		total_copied += copied;
-
-		/* Return to btrfs_file_write_iter to fault page */
-		if (unlikely(copied == 0))
-			break;
-
-		if (copied < PAGE_SIZE - offset) {
-			offset += copied;
-		} else {
+		offset += copied;
+		if (offset == PAGE_SIZE) {
 			pg++;
 			offset = 0;
 		}
diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index 09ef2a4d25ed..4722fa31a185 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -1171,14 +1171,12 @@ static ssize_t fuse_fill_write_pages(struct fuse_io_args *ia,
 		if (mapping_writably_mapped(mapping))
 			flush_dcache_page(page);
 
-		tmp = iov_iter_copy_from_user_atomic(page, ii, offset, bytes);
+		tmp = copy_page_from_iter_atomic(page, offset, bytes, ii);
 		flush_dcache_page(page);
 
-		iov_iter_advance(ii, tmp);
 		if (!tmp) {
 			unlock_page(page);
 			put_page(page);
-			bytes = min(bytes, iov_iter_single_seg_count(ii));
 			goto again;
 		}
 
diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index 0065781935c7..41da4f14c00b 100644
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -746,10 +746,6 @@ 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;
@@ -764,30 +760,29 @@ again:
 		if (mapping_writably_mapped(inode->i_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);
 
-		copied = iomap_write_end(inode, pos, bytes, copied, page, iomap,
+		status = iomap_write_end(inode, pos, bytes, copied, page, iomap,
 				srcmap);
 
-		cond_resched();
+		if (unlikely(copied != status))
+			iov_iter_revert(i, copied - status);
 
-		iov_iter_advance(i, copied);
-		if (unlikely(copied == 0)) {
+		cond_resched();
+		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 iomap_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;
-		length -= copied;
+		pos += status;
+		written += status;
+		length -= status;
 
 		balance_dirty_pages_ratelimited(inode->i_mapping);
 	} while (iov_iter_count(i) && length);
diff --git a/fs/ntfs/file.c b/fs/ntfs/file.c
index e5aab265dff1..ab4f3362466d 100644
--- a/fs/ntfs/file.c
+++ b/fs/ntfs/file.c
@@ -1684,20 +1684,17 @@ static size_t ntfs_copy_from_user_iter(struct page **pages, unsigned nr_pages,
 {
 	struct page **last_page = pages + nr_pages;
 	size_t total = 0;
-	struct iov_iter data = *i;
 	unsigned len, copied;
 
 	do {
 		len = PAGE_SIZE - ofs;
 		if (len > bytes)
 			len = bytes;
-		copied = iov_iter_copy_from_user_atomic(*pages, &data, ofs,
-				len);
+		copied = copy_page_from_iter_atomic(*pages, ofs, len, i);
 		total += copied;
 		bytes -= copied;
 		if (!bytes)
 			break;
-		iov_iter_advance(&data, copied);
 		if (copied < len)
 			goto err;
 		ofs = 0;
@@ -1866,34 +1863,24 @@ again:
 		if (likely(copied == bytes)) {
 			status = ntfs_commit_pages_after_write(pages, do_pages,
 					pos, bytes);
-			if (!status)
-				status = bytes;
 		}
 		do {
 			unlock_page(pages[--do_pages]);
 			put_page(pages[do_pages]);
 		} while (do_pages);
-		if (unlikely(status < 0))
+		if (unlikely(status < 0)) {
+			iov_iter_revert(i, copied);
 			break;
-		copied = status;
+		}
 		cond_resched();
-		if (unlikely(!copied)) {
-			size_t sc;
-
-			/*
-			 * We failed to copy anything.  Fall back to single
-			 * segment length write.
-			 *
-			 * This is needed to avoid possible livelock in the
-			 * case that all segments in the iov cannot be copied
-			 * at once without a pagefault.
-			 */
-			sc = iov_iter_single_seg_count(i);
-			if (bytes > sc)
-				bytes = sc;
+		if (unlikely(copied < bytes)) {
+			iov_iter_revert(i, copied);
+			if (copied)
+				bytes = copied;
+			else if (bytes > PAGE_SIZE - ofs)
+				bytes = PAGE_SIZE - ofs;
 			goto again;
 		}
-		iov_iter_advance(i, copied);
 		pos += copied;
 		written += copied;
 		balance_dirty_pages_ratelimited(mapping);