orangefs: make pvfs2_inode_read() take iov_iter

... and make the only caller use page-backed iov_iter,
getting rid of kmap/kunmap *and* of the bug with
attempted use of iovec-backed copy_page_to_iter()
on a kernel pointer.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Mike Marshall <hubcap@omnibond.com>

fs/orangefs/file.c

@@ -369,22 +369,17 @@ static ssize_t do_readv_writev(enum PVFS_io_type type, struct file *file,
  * Data may be placed either in a user or kernel buffer.
  */
 ssize_t pvfs2_inode_read(struct inode *inode,
-			 char __user *buf,
-			 size_t count,
+			 struct iov_iter *iter,
 			 loff_t *offset,
 			 loff_t readahead_size)
 {
 	struct pvfs2_inode_s *pvfs2_inode = PVFS2_I(inode);
+	size_t count = iov_iter_count(iter);
 	size_t bufmap_size;
-	struct iovec vec;
-	struct iov_iter iter;
 	ssize_t ret = -EINVAL;
 
 	g_pvfs2_stats.reads++;
 
-	vec.iov_base = buf;
-	vec.iov_len = count;
-
 	bufmap_size = pvfs_bufmap_size_query();
 	if (count > bufmap_size) {
 		gossip_debug(GOSSIP_FILE_DEBUG,
@@ -400,8 +395,7 @@ ssize_t pvfs2_inode_read(struct inode *inode,
 		     count,
 		     llu(*offset));
 
-	iov_iter_init(&iter, READ, &vec, 1, count);
-	ret = wait_for_direct_io(PVFS_IO_READ, inode, offset, &iter,
+	ret = wait_for_direct_io(PVFS_IO_READ, inode, offset, iter,
 			count, readahead_size);
 	if (ret > 0)
 		*offset += ret;

fs/orangefs/inode.c

@@ -14,18 +14,20 @@
 
 static int read_one_page(struct page *page)
 {
-	void *page_data;
 	int ret;
 	int max_block;
 	ssize_t bytes_read = 0;
 	struct inode *inode = page->mapping->host;
 	const __u32 blocksize = PAGE_CACHE_SIZE;	/* inode->i_blksize */
 	const __u32 blockbits = PAGE_CACHE_SHIFT;	/* inode->i_blkbits */
+	struct iov_iter to;
+	struct bio_vec bv = {.bv_page = page, .bv_len = PAGE_SIZE};
+
+	iov_iter_bvec(&to, ITER_BVEC | READ, &bv, 1, PAGE_SIZE);
 
 	gossip_debug(GOSSIP_INODE_DEBUG,
 		    "pvfs2_readpage called with page %p\n",
 		     page);
-	page_data = pvfs2_kmap(page);
 
 	max_block = ((inode->i_size / blocksize) + 1);
 
@@ -33,16 +35,12 @@ static int read_one_page(struct page *page)
 		loff_t blockptr_offset = (((loff_t) page->index) << blockbits);
 
 		bytes_read = pvfs2_inode_read(inode,
-					      (char __user *) page_data,
-					      blocksize,
+					      &to,
 					      &blockptr_offset,
 					      inode->i_size);
 	}
-	/* only zero remaining unread portions of the page data */
-	if (bytes_read > 0)
-		memset(page_data + bytes_read, 0, blocksize - bytes_read);
-	else
-		memset(page_data, 0, blocksize);
+	/* this will only zero remaining unread portions of the page data */
+	iov_iter_zero(~0U, &to);
 	/* takes care of potential aliasing */
 	flush_dcache_page(page);
 	if (bytes_read < 0) {
@@ -54,7 +52,6 @@ static int read_one_page(struct page *page)
 			ClearPageError(page);
 		ret = 0;
 	}
-	pvfs2_kunmap(page);
 	/* unlock the page after the ->readpage() routine completes */
 	unlock_page(page);
 	return ret;

fs/orangefs/pvfs2-kernel.h

@@ -605,8 +605,7 @@ struct inode *pvfs2_iget(struct super_block *sb,
 			 struct pvfs2_object_kref *ref);
 
 ssize_t pvfs2_inode_read(struct inode *inode,
-			 char __user *buf,
-			 size_t count,
+			 struct iov_iter *iter,
 			 loff_t *offset,
 			 loff_t readahead_size);