Merge tag 'pull-work.iov_iter-rebased' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

Pull more iov_iter updates from Al Viro:

 - more new_sync_{read,write}() speedups - ITER_UBUF introduction

 - ITER_PIPE cleanups

 - unification of iov_iter_get_pages/iov_iter_get_pages_alloc and
   switching them to advancing semantics

 - making ITER_PIPE take high-order pages without splitting them

 - handling copy_page_from_iter() for high-order pages properly

* tag 'pull-work.iov_iter-rebased' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (32 commits)
  fix copy_page_from_iter() for compound destinations
  hugetlbfs: copy_page_to_iter() can deal with compound pages
  copy_page_to_iter(): don't split high-order page in case of ITER_PIPE
  expand those iov_iter_advance()...
  pipe_get_pages(): switch to append_pipe()
  get rid of non-advancing variants
  ceph: switch the last caller of iov_iter_get_pages_alloc()
  9p: convert to advancing variant of iov_iter_get_pages_alloc()
  af_alg_make_sg(): switch to advancing variant of iov_iter_get_pages()
  iter_to_pipe(): switch to advancing variant of iov_iter_get_pages()
  block: convert to advancing variants of iov_iter_get_pages{,_alloc}()
  iov_iter: advancing variants of iov_iter_get_pages{,_alloc}()
  iov_iter: saner helper for page array allocation
  fold __pipe_get_pages() into pipe_get_pages()
  ITER_XARRAY: don't open-code DIV_ROUND_UP()
  unify the rest of iov_iter_get_pages()/iov_iter_get_pages_alloc() guts
  unify xarray_get_pages() and xarray_get_pages_alloc()
  unify pipe_get_pages() and pipe_get_pages_alloc()
  iov_iter_get_pages(): sanity-check arguments
  iov_iter_get_pages_alloc(): lift freeing pages array on failure exits into wrapper
  ...

block/bio.c

@@ -1200,7 +1200,7 @@ static int __bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter)
 	struct page **pages = (struct page **)bv;
 	ssize_t size, left;
 	unsigned len, i = 0;
-	size_t offset;
+	size_t offset, trim;
 	int ret = 0;
 
 	/*
@@ -1218,16 +1218,19 @@ static int __bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter)
 	 * result to ensure the bio's total size is correct. The remainder of
 	 * the iov data will be picked up in the next bio iteration.
 	 */
-	size = iov_iter_get_pages(iter, pages, UINT_MAX - bio->bi_iter.bi_size,
+	size = iov_iter_get_pages2(iter, pages, UINT_MAX - bio->bi_iter.bi_size,
 				  nr_pages, &offset);
-	if (size > 0) {
-		nr_pages = DIV_ROUND_UP(offset + size, PAGE_SIZE);
-		size = ALIGN_DOWN(size, bdev_logical_block_size(bio->bi_bdev));
-	} else
-		nr_pages = 0;
+	if (unlikely(size <= 0))
+		return size ? size : -EFAULT;
 
-	if (unlikely(size <= 0)) {
-		ret = size ? size : -EFAULT;
+	nr_pages = DIV_ROUND_UP(offset + size, PAGE_SIZE);
+
+	trim = size & (bdev_logical_block_size(bio->bi_bdev) - 1);
+	iov_iter_revert(iter, trim);
+
+	size -= trim;
+	if (unlikely(!size)) {
+		ret = -EFAULT;
 		goto out;
 	}
 
@@ -1246,7 +1249,7 @@ static int __bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter)
 		offset = 0;
 	}
 
-	iov_iter_advance(iter, size - left);
+	iov_iter_revert(iter, left);
 out:
 	while (i < nr_pages)
 		put_page(pages[i++]);

block/blk-map.c

@@ -254,7 +254,7 @@ static int bio_map_user_iov(struct request *rq, struct iov_iter *iter,
 		size_t offs, added = 0;
 		int npages;
 
-		bytes = iov_iter_get_pages_alloc(iter, &pages, LONG_MAX, &offs);
+		bytes = iov_iter_get_pages_alloc2(iter, &pages, LONG_MAX, &offs);
 		if (unlikely(bytes <= 0)) {
 			ret = bytes ? bytes : -EFAULT;
 			goto out_unmap;
@@ -284,7 +284,6 @@ static int bio_map_user_iov(struct request *rq, struct iov_iter *iter,
 				bytes -= n;
 				offs = 0;
 			}
-			iov_iter_advance(iter, added);
 		}
 		/*
 		 * release the pages we didn't map into the bio, if any
@@ -293,8 +292,10 @@ static int bio_map_user_iov(struct request *rq, struct iov_iter *iter,
 			put_page(pages[j++]);
 		kvfree(pages);
 		/* couldn't stuff something into bio? */
-		if (bytes)
+		if (bytes) {
+			iov_iter_revert(iter, bytes);
 			break;
+		}
 	}
 
 	ret = blk_rq_append_bio(rq, bio);

block/fops.c

@@ -75,7 +75,7 @@ static ssize_t __blkdev_direct_IO_simple(struct kiocb *iocb,
 
 	if (iov_iter_rw(iter) == READ) {
 		bio_init(&bio, bdev, vecs, nr_pages, REQ_OP_READ);
-		if (iter_is_iovec(iter))
+		if (user_backed_iter(iter))
 			should_dirty = true;
 	} else {
 		bio_init(&bio, bdev, vecs, nr_pages, dio_bio_write_op(iocb));
@@ -204,7 +204,7 @@ static ssize_t __blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter,
 	}
 
 	dio->size = 0;
-	if (is_read && iter_is_iovec(iter))
+	if (is_read && user_backed_iter(iter))
 		dio->flags |= DIO_SHOULD_DIRTY;
 
 	blk_start_plug(&plug);
@@ -335,7 +335,7 @@ static ssize_t __blkdev_direct_IO_async(struct kiocb *iocb,
 	dio->size = bio->bi_iter.bi_size;
 
 	if (is_read) {
-		if (iter_is_iovec(iter)) {
+		if (user_backed_iter(iter)) {
 			dio->flags |= DIO_SHOULD_DIRTY;
 			bio_set_pages_dirty(bio);
 		}

crypto/af_alg.c

@@ -404,7 +404,7 @@ int af_alg_make_sg(struct af_alg_sgl *sgl, struct iov_iter *iter, int len)
 	ssize_t n;
 	int npages, i;
 
-	n = iov_iter_get_pages(iter, sgl->pages, len, ALG_MAX_PAGES, &off);
+	n = iov_iter_get_pages2(iter, sgl->pages, len, ALG_MAX_PAGES, &off);
 	if (n < 0)
 		return n;
 
@@ -1191,7 +1191,6 @@ int af_alg_get_rsgl(struct sock *sk, struct msghdr *msg, int flags,
 		len += err;
 		atomic_add(err, &ctx->rcvused);
 		rsgl->sg_num_bytes = err;
-		iov_iter_advance(&msg->msg_iter, err);
 	}
 
 	*outlen = len;

crypto/algif_hash.c

@@ -102,11 +102,12 @@ static int hash_sendmsg(struct socket *sock, struct msghdr *msg,
 		err = crypto_wait_req(crypto_ahash_update(&ctx->req),
 				      &ctx->wait);
 		af_alg_free_sg(&ctx->sgl);
-		if (err)
+		if (err) {
+			iov_iter_revert(&msg->msg_iter, len);
 			goto unlock;
+		}
 
 		copied += len;
-		iov_iter_advance(&msg->msg_iter, len);
 	}
 
 	err = 0;

drivers/vhost/scsi.c

@@ -643,14 +643,12 @@ vhost_scsi_map_to_sgl(struct vhost_scsi_cmd *cmd,
 	size_t offset;
 	unsigned int npages = 0;
 
-	bytes = iov_iter_get_pages(iter, pages, LONG_MAX,
+	bytes = iov_iter_get_pages2(iter, pages, LONG_MAX,
 				VHOST_SCSI_PREALLOC_UPAGES, &offset);
 	/* No pages were pinned */
 	if (bytes <= 0)
 		return bytes < 0 ? bytes : -EFAULT;
 
-	iov_iter_advance(iter, bytes);
-
 	while (bytes) {
 		unsigned n = min_t(unsigned, PAGE_SIZE - offset, bytes);
 		sg_set_page(sg++, pages[npages++], n, offset);

fs/ceph/addr.c

@@ -329,7 +329,7 @@ static void ceph_netfs_issue_read(struct netfs_io_subrequest *subreq)
 
 	dout("%s: pos=%llu orig_len=%zu len=%llu\n", __func__, subreq->start, subreq->len, len);
 	iov_iter_xarray(&iter, READ, &rreq->mapping->i_pages, subreq->start, len);
-	err = iov_iter_get_pages_alloc(&iter, &pages, len, &page_off);
+	err = iov_iter_get_pages_alloc2(&iter, &pages, len, &page_off);
 	if (err < 0) {
 		dout("%s: iov_ter_get_pages_alloc returned %d\n", __func__, err);
 		goto out;

fs/ceph/file.c

@@ -95,12 +95,11 @@ static ssize_t __iter_get_bvecs(struct iov_iter *iter, size_t maxsize,
 		size_t start;
 		int idx = 0;
 
-		bytes = iov_iter_get_pages(iter, pages, maxsize - size,
+		bytes = iov_iter_get_pages2(iter, pages, maxsize - size,
 					   ITER_GET_BVECS_PAGES, &start);
 		if (bytes < 0)
 			return size ?: bytes;
 
-		iov_iter_advance(iter, bytes);
 		size += bytes;
 
 		for ( ; bytes; idx++, bvec_idx++) {
@@ -1262,7 +1261,7 @@ ceph_direct_read_write(struct kiocb *iocb, struct iov_iter *iter,
 	size_t count = iov_iter_count(iter);
 	loff_t pos = iocb->ki_pos;
 	bool write = iov_iter_rw(iter) == WRITE;
-	bool should_dirty = !write && iter_is_iovec(iter);
+	bool should_dirty = !write && user_backed_iter(iter);
 
 	if (write && ceph_snap(file_inode(file)) != CEPH_NOSNAP)
 		return -EROFS;

fs/cifs/file.c

@@ -3276,7 +3276,7 @@ cifs_write_from_iter(loff_t offset, size_t len, struct iov_iter *from,
 		if (ctx->direct_io) {
 			ssize_t result;
 
-			result = iov_iter_get_pages_alloc(
+			result = iov_iter_get_pages_alloc2(
 				from, &pagevec, cur_len, &start);
 			if (result < 0) {
 				cifs_dbg(VFS,
@@ -3290,7 +3290,6 @@ cifs_write_from_iter(loff_t offset, size_t len, struct iov_iter *from,
 				break;
 			}
 			cur_len = (size_t)result;
-			iov_iter_advance(from, cur_len);
 
 			nr_pages =
 				(cur_len + start + PAGE_SIZE - 1) / PAGE_SIZE;
@@ -4012,7 +4011,7 @@ cifs_send_async_read(loff_t offset, size_t len, struct cifsFileInfo *open_file,
 		if (ctx->direct_io) {
 			ssize_t result;
 
-			result = iov_iter_get_pages_alloc(
+			result = iov_iter_get_pages_alloc2(
 					&direct_iov, &pagevec,
 					cur_len, &start);
 			if (result < 0) {
@@ -4028,7 +4027,6 @@ cifs_send_async_read(loff_t offset, size_t len, struct cifsFileInfo *open_file,
 				break;
 			}
 			cur_len = (size_t)result;
-			iov_iter_advance(&direct_iov, cur_len);
 
 			rdata = cifs_readdata_direct_alloc(
 					pagevec, cifs_uncached_readv_complete);
@@ -4258,7 +4256,7 @@ static ssize_t __cifs_readv(
 	if (!is_sync_kiocb(iocb))
 		ctx->iocb = iocb;
 
-	if (iter_is_iovec(to))
+	if (user_backed_iter(to))
 		ctx->should_dirty = true;
 
 	if (direct) {

fs/cifs/misc.c

@@ -1022,7 +1022,7 @@ setup_aio_ctx_iter(struct cifs_aio_ctx *ctx, struct iov_iter *iter, int rw)
 	saved_len = count;
 
 	while (count && npages < max_pages) {
-		rc = iov_iter_get_pages(iter, pages, count, max_pages, &start);
+		rc = iov_iter_get_pages2(iter, pages, count, max_pages, &start);
 		if (rc < 0) {
 			cifs_dbg(VFS, "Couldn't get user pages (rc=%zd)\n", rc);
 			break;
@@ -1034,7 +1034,6 @@ setup_aio_ctx_iter(struct cifs_aio_ctx *ctx, struct iov_iter *iter, int rw)
 			break;
 		}
 
-		iov_iter_advance(iter, rc);
 		count -= rc;
 		rc += start;
 		cur_npages = DIV_ROUND_UP(rc, PAGE_SIZE);

fs/direct-io.c

@@ -169,7 +169,7 @@ static inline int dio_refill_pages(struct dio *dio, struct dio_submit *sdio)
 	const enum req_op dio_op = dio->opf & REQ_OP_MASK;
 	ssize_t ret;
 
-	ret = iov_iter_get_pages(sdio->iter, dio->pages, LONG_MAX, DIO_PAGES,
+	ret = iov_iter_get_pages2(sdio->iter, dio->pages, LONG_MAX, DIO_PAGES,
 				&sdio->from);
 
 	if (ret < 0 && sdio->blocks_available && dio_op == REQ_OP_WRITE) {
@@ -191,7 +191,6 @@ static inline int dio_refill_pages(struct dio *dio, struct dio_submit *sdio)
 	}
 
 	if (ret >= 0) {
-		iov_iter_advance(sdio->iter, ret);
 		ret += sdio->from;
 		sdio->head = 0;
 		sdio->tail = (ret + PAGE_SIZE - 1) / PAGE_SIZE;
@@ -1251,7 +1250,7 @@ ssize_t __blockdev_direct_IO(struct kiocb *iocb, struct inode *inode,
 	spin_lock_init(&dio->bio_lock);
 	dio->refcount = 1;
 
-	dio->should_dirty = iter_is_iovec(iter) && iov_iter_rw(iter) == READ;
+	dio->should_dirty = user_backed_iter(iter) && iov_iter_rw(iter) == READ;
 	sdio.iter = iter;
 	sdio.final_block_in_request = end >> blkbits;
 

fs/fuse/dev.c

@@ -730,14 +730,13 @@ static int fuse_copy_fill(struct fuse_copy_state *cs)
 		}
 	} else {
 		size_t off;
-		err = iov_iter_get_pages(cs->iter, &page, PAGE_SIZE, 1, &off);
+		err = iov_iter_get_pages2(cs->iter, &page, PAGE_SIZE, 1, &off);
 		if (err < 0)
 			return err;
 		BUG_ON(!err);
 		cs->len = err;
 		cs->offset = off;
 		cs->pg = page;
-		iov_iter_advance(cs->iter, err);
 	}
 
 	return lock_request(cs->req);
@@ -1356,7 +1355,7 @@ static ssize_t fuse_dev_read(struct kiocb *iocb, struct iov_iter *to)
 	if (!fud)
 		return -EPERM;
 
-	if (!iter_is_iovec(to))
+	if (!user_backed_iter(to))
 		return -EINVAL;
 
 	fuse_copy_init(&cs, 1, to);
@@ -1949,7 +1948,7 @@ static ssize_t fuse_dev_write(struct kiocb *iocb, struct iov_iter *from)
 	if (!fud)
 		return -EPERM;
 
-	if (!iter_is_iovec(from))
+	if (!user_backed_iter(from))
 		return -EINVAL;
 
 	fuse_copy_init(&cs, 0, from);

fs/fuse/file.c

@@ -1414,14 +1414,13 @@ static int fuse_get_user_pages(struct fuse_args_pages *ap, struct iov_iter *ii,
 	while (nbytes < *nbytesp && ap->num_pages < max_pages) {
 		unsigned npages;
 		size_t start;
-		ret = iov_iter_get_pages(ii, &ap->pages[ap->num_pages],
+		ret = iov_iter_get_pages2(ii, &ap->pages[ap->num_pages],
 					*nbytesp - nbytes,
 					max_pages - ap->num_pages,
 					&start);
 		if (ret < 0)
 			break;
 
-		iov_iter_advance(ii, ret);
 		nbytes += ret;
 
 		ret += start;
@@ -1478,7 +1477,7 @@ ssize_t fuse_direct_io(struct fuse_io_priv *io, struct iov_iter *iter,
 			inode_unlock(inode);
 	}
 
-	io->should_dirty = !write && iter_is_iovec(iter);
+	io->should_dirty = !write && user_backed_iter(iter);
 	while (count) {
 		ssize_t nres;
 		fl_owner_t owner = current->files;

fs/gfs2/file.c

@@ -780,7 +780,7 @@ static inline bool should_fault_in_pages(struct iov_iter *i,
 
 	if (!count)
 		return false;
-	if (!iter_is_iovec(i))
+	if (!user_backed_iter(i))
 		return false;
 
 	size = PAGE_SIZE;

fs/hugetlbfs/inode.c

@@ -282,35 +282,6 @@ hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
 }
 #endif
 
-static size_t
-hugetlbfs_read_actor(struct page *page, unsigned long offset,
-			struct iov_iter *to, unsigned long size)
-{
-	size_t copied = 0;
-	int i, chunksize;
-
-	/* Find which 4k chunk and offset with in that chunk */
-	i = offset >> PAGE_SHIFT;
-	offset = offset & ~PAGE_MASK;
-
-	while (size) {
-		size_t n;
-		chunksize = PAGE_SIZE;
-		if (offset)
-			chunksize -= offset;
-		if (chunksize > size)
-			chunksize = size;
-		n = copy_page_to_iter(&page[i], offset, chunksize, to);
-		copied += n;
-		if (n != chunksize)
-			return copied;
-		offset = 0;
-		size -= chunksize;
-		i++;
-	}
-	return copied;
-}
-
 /*
  * Support for read() - Find the page attached to f_mapping and copy out the
  * data. This provides functionality similar to filemap_read().
@@ -360,7 +331,7 @@ static ssize_t hugetlbfs_read_iter(struct kiocb *iocb, struct iov_iter *to)
 			/*
 			 * We have the page, copy it to user space buffer.
 			 */
-			copied = hugetlbfs_read_actor(page, offset, to, nr);
+			copied = copy_page_to_iter(page, offset, nr, to);
 			put_page(page);
 		}
 		offset += copied;

fs/iomap/direct-io.c

@@ -533,7 +533,7 @@ __iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
 			iomi.flags |= IOMAP_NOWAIT;
 		}
 
-		if (iter_is_iovec(iter))
+		if (user_backed_iter(iter))
 			dio->flags |= IOMAP_DIO_DIRTY;
 	} else {
 		iomi.flags |= IOMAP_WRITE;

fs/nfs/direct.c

@@ -364,13 +364,12 @@ static ssize_t nfs_direct_read_schedule_iovec(struct nfs_direct_req *dreq,
 		size_t pgbase;
 		unsigned npages, i;
 
-		result = iov_iter_get_pages_alloc(iter, &pagevec, 
+		result = iov_iter_get_pages_alloc2(iter, &pagevec,
 						  rsize, &pgbase);
 		if (result < 0)
 			break;
 	
 		bytes = result;
-		iov_iter_advance(iter, bytes);
 		npages = (result + pgbase + PAGE_SIZE - 1) / PAGE_SIZE;
 		for (i = 0; i < npages; i++) {
 			struct nfs_page *req;
@@ -478,7 +477,7 @@ ssize_t nfs_file_direct_read(struct kiocb *iocb, struct iov_iter *iter,
 	if (!is_sync_kiocb(iocb))
 		dreq->iocb = iocb;
 
-	if (iter_is_iovec(iter))
+	if (user_backed_iter(iter))
 		dreq->flags = NFS_ODIRECT_SHOULD_DIRTY;
 
 	if (!swap)
@@ -812,13 +811,12 @@ static ssize_t nfs_direct_write_schedule_iovec(struct nfs_direct_req *dreq,
 		size_t pgbase;
 		unsigned npages, i;
 
-		result = iov_iter_get_pages_alloc(iter, &pagevec, 
+		result = iov_iter_get_pages_alloc2(iter, &pagevec,
 						  wsize, &pgbase);
 		if (result < 0)
 			break;
 
 		bytes = result;
-		iov_iter_advance(iter, bytes);
 		npages = (result + pgbase + PAGE_SIZE - 1) / PAGE_SIZE;
 		for (i = 0; i < npages; i++) {
 			struct nfs_page *req;

fs/read_write.c

@@ -378,14 +378,13 @@ EXPORT_SYMBOL(rw_verify_area);
 
 static ssize_t new_sync_read(struct file *filp, char __user *buf, size_t len, loff_t *ppos)
 {
-	struct iovec iov = { .iov_base = buf, .iov_len = len };
 	struct kiocb kiocb;
 	struct iov_iter iter;
 	ssize_t ret;
 
 	init_sync_kiocb(&kiocb, filp);
 	kiocb.ki_pos = (ppos ? *ppos : 0);
-	iov_iter_init(&iter, READ, &iov, 1, len);
+	iov_iter_ubuf(&iter, READ, buf, len);
 
 	ret = call_read_iter(filp, &kiocb, &iter);
 	BUG_ON(ret == -EIOCBQUEUED);
@@ -481,14 +480,13 @@ ssize_t vfs_read(struct file *file, char __user *buf, size_t count, loff_t *pos)
 
 static ssize_t new_sync_write(struct file *filp, const char __user *buf, size_t len, loff_t *ppos)
 {
-	struct iovec iov = { .iov_base = (void __user *)buf, .iov_len = len };
 	struct kiocb kiocb;
 	struct iov_iter iter;
 	ssize_t ret;
 
 	init_sync_kiocb(&kiocb, filp);
 	kiocb.ki_pos = (ppos ? *ppos : 0);
-	iov_iter_init(&iter, WRITE, &iov, 1, len);
+	iov_iter_ubuf(&iter, WRITE, (void __user *)buf, len);
 
 	ret = call_write_iter(filp, &kiocb, &iter);
 	BUG_ON(ret == -EIOCBQUEUED);

fs/splice.c

@@ -301,11 +301,9 @@ ssize_t generic_file_splice_read(struct file *in, loff_t *ppos,
 {
 	struct iov_iter to;
 	struct kiocb kiocb;
-	unsigned int i_head;
 	int ret;
 
 	iov_iter_pipe(&to, READ, pipe, len);
-	i_head = to.head;
 	init_sync_kiocb(&kiocb, in);
 	kiocb.ki_pos = *ppos;
 	ret = call_read_iter(in, &kiocb, &to);
@@ -313,9 +311,8 @@ ssize_t generic_file_splice_read(struct file *in, loff_t *ppos,
 		*ppos = kiocb.ki_pos;
 		file_accessed(in);
 	} else if (ret < 0) {
-		to.head = i_head;
-		to.iov_offset = 0;
-		iov_iter_advance(&to, 0); /* to free what was emitted */
+		/* free what was emitted */
+		pipe_discard_from(pipe, to.start_head);
 		/*
 		 * callers of ->splice_read() expect -EAGAIN on
 		 * "can't put anything in there", rather than -EFAULT.
@@ -1161,39 +1158,40 @@ static int iter_to_pipe(struct iov_iter *from,
 	};
 	size_t total = 0;
 	int ret = 0;
-	bool failed = false;
 
-	while (iov_iter_count(from) && !failed) {
+	while (iov_iter_count(from)) {
 		struct page *pages[16];
-		ssize_t copied;
+		ssize_t left;
 		size_t start;
-		int n;
+		int i, n;
 
-		copied = iov_iter_get_pages(from, pages, ~0UL, 16, &start);
-		if (copied <= 0) {
-			ret = copied;
+		left = iov_iter_get_pages2(from, pages, ~0UL, 16, &start);
+		if (left <= 0) {
+			ret = left;
 			break;
 		}
 
-		for (n = 0; copied; n++, start = 0) {
-			int size = min_t(int, copied, PAGE_SIZE - start);
-			if (!failed) {
-				buf.page = pages[n];
-				buf.offset = start;
-				buf.len = size;
-				ret = add_to_pipe(pipe, &buf);
-				if (unlikely(ret < 0)) {
-					failed = true;
-				} else {
-					iov_iter_advance(from, ret);
-					total += ret;
-				}
-			} else {
-				put_page(pages[n]);
+		n = DIV_ROUND_UP(left + start, PAGE_SIZE);
+		for (i = 0; i < n; i++) {
+			int size = min_t(int, left, PAGE_SIZE - start);
+
+			buf.page = pages[i];
+			buf.offset = start;
+			buf.len = size;
+			ret = add_to_pipe(pipe, &buf);
+			if (unlikely(ret < 0)) {
+				iov_iter_revert(from, left);
+				// this one got dropped by add_to_pipe()
+				while (++i < n)
+					put_page(pages[i]);
+				goto out;
 			}
-			copied -= size;
+			total += ret;
+			left -= size;
+			start = 0;
 		}
 	}
+out:
 	return total ? total : ret;
 }
 

include/linux/pipe_fs_i.h

@@ -156,26 +156,6 @@ static inline bool pipe_full(unsigned int head, unsigned int tail,
 	return pipe_occupancy(head, tail) >= limit;
 }
 
-/**
- * pipe_space_for_user - Return number of slots available to userspace
- * @head: The pipe ring head pointer
- * @tail: The pipe ring tail pointer
- * @pipe: The pipe info structure
- */
-static inline unsigned int pipe_space_for_user(unsigned int head, unsigned int tail,
-					       struct pipe_inode_info *pipe)
-{
-	unsigned int p_occupancy, p_space;
-
-	p_occupancy = pipe_occupancy(head, tail);
-	if (p_occupancy >= pipe->max_usage)
-		return 0;
-	p_space = pipe->ring_size - p_occupancy;
-	if (p_space > pipe->max_usage)
-		p_space = pipe->max_usage;
-	return p_space;
-}
-
 /**
  * pipe_buf_get - get a reference to a pipe_buffer
  * @pipe:	the pipe that the buffer belongs to