ceph: refactor ceph_sync_read()

Avoid allocating memory for the entire user request: striped_read()
does a synchronous OSD request per object, so it doesn't need more than
object size worth of pages at a time.

[ Preserve the comment, changelog. ]
Signed-off-by: "Yan, Zheng" <zyan@redhat.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

fs/ceph/file.c

@@ -556,91 +556,27 @@ enum {
 	READ_INLINE =  3,
 };
 
-/*
- * Read a range of bytes striped over one or more objects.  Iterate over
- * objects we stripe over.  (That's not atomic, but good enough for now.)
- *
- * If we get a short result from the OSD, check against i_size; we need to
- * only return a short read to the caller if we hit EOF.
- */
-static int striped_read(struct inode *inode,
-			u64 pos, u64 len,
-			struct page **pages, int num_pages,
-			int page_align, int *checkeof)
-{
-	struct ceph_fs_client *fsc = ceph_inode_to_client(inode);
-	struct ceph_inode_info *ci = ceph_inode(inode);
-	u64 this_len;
-	loff_t i_size;
-	int page_idx;
-	int ret, read = 0;
-	bool hit_stripe, was_short;
-
-	/*
-	 * we may need to do multiple reads.  not atomic, unfortunately.
-	 */
-more:
-	this_len = len;
-	page_idx = (page_align + read) >> PAGE_SHIFT;
-	ret = ceph_osdc_readpages(&fsc->client->osdc, ceph_vino(inode),
-				  &ci->i_layout, pos, &this_len,
-				  ci->i_truncate_seq, ci->i_truncate_size,
-				  pages + page_idx, num_pages - page_idx,
-				  ((page_align + read) & ~PAGE_MASK));
-	if (ret == -ENOENT)
-		ret = 0;
-	hit_stripe = this_len < len;
-	was_short = ret >= 0 && ret < this_len;
-	dout("striped_read %llu~%llu (read %u) got %d%s%s\n", pos, len, read,
-	     ret, hit_stripe ? " HITSTRIPE" : "", was_short ? " SHORT" : "");
-
-	i_size = i_size_read(inode);
-	if (ret >= 0) {
-		if (was_short && (pos + ret < i_size)) {
-			int zlen = min(this_len - ret, i_size - pos - ret);
-			int zoff = page_align + read + ret;
-			dout(" zero gap %llu to %llu\n",
-			     pos + ret, pos + ret + zlen);
-			ceph_zero_page_vector_range(zoff, zlen, pages);
-			ret += zlen;
-		}
-
-		read += ret;
-		pos += ret;
-		len -= ret;
-
-		/* hit stripe and need continue*/
-		if (len && hit_stripe && pos < i_size)
-			goto more;
-	}
-
-	if (read > 0) {
-		ret = read;
-		/* did we bounce off eof? */
-		if (pos + len > i_size)
-			*checkeof = CHECK_EOF;
-	}
-
-	dout("striped_read returns %d\n", ret);
-	return ret;
-}
-
 /*
  * Completely synchronous read and write methods.  Direct from __user
  * buffer to osd, or directly to user pages (if O_DIRECT).
  *
- * If the read spans object boundary, just do multiple reads.
+ * If the read spans object boundary, just do multiple reads.  (That's not
+ * atomic, but good enough for now.)
+ *
+ * If we get a short result from the OSD, check against i_size; we need to
+ * only return a short read to the caller if we hit EOF.
  */
 static ssize_t ceph_sync_read(struct kiocb *iocb, struct iov_iter *to,
-			      int *checkeof)
+			      int *retry_op)
 {
 	struct file *file = iocb->ki_filp;
 	struct inode *inode = file_inode(file);
-	struct page **pages;
-	u64 off = iocb->ki_pos;
-	int num_pages;
+	struct ceph_inode_info *ci = ceph_inode(inode);
+	struct ceph_fs_client *fsc = ceph_inode_to_client(inode);
+	struct ceph_osd_client *osdc = &fsc->client->osdc;
 	ssize_t ret;
-	size_t len = iov_iter_count(to);
+	u64 off = iocb->ki_pos;
+	u64 len = iov_iter_count(to);
 
 	dout("sync_read on file %p %llu~%u %s\n", file, off, (unsigned)len,
 	     (file->f_flags & O_DIRECT) ? "O_DIRECT" : "");
@@ -653,61 +589,118 @@ static ssize_t ceph_sync_read(struct kiocb *iocb, struct iov_iter *to,
 	 * but it will at least behave sensibly when they are
 	 * in sequence.
 	 */
-	ret = filemap_write_and_wait_range(inode->i_mapping, off,
-						off + len);
+	ret = filemap_write_and_wait_range(inode->i_mapping, off, off + len);
 	if (ret < 0)
 		return ret;
 
-	if (unlikely(to->type & ITER_PIPE)) {
+	ret = 0;
+	while ((len = iov_iter_count(to)) > 0) {
+		struct ceph_osd_request *req;
+		struct page **pages;
+		int num_pages;
 		size_t page_off;
-		ret = iov_iter_get_pages_alloc(to, &pages, len,
-					       &page_off);
-		if (ret <= 0)
-			return -ENOMEM;
-		num_pages = DIV_ROUND_UP(ret + page_off, PAGE_SIZE);
+		u64 i_size;
+		bool more;
+
+		req = ceph_osdc_new_request(osdc, &ci->i_layout,
+					ci->i_vino, off, &len, 0, 1,
+					CEPH_OSD_OP_READ, CEPH_OSD_FLAG_READ,
+					NULL, ci->i_truncate_seq,
+					ci->i_truncate_size, false);
+		if (IS_ERR(req)) {
+			ret = PTR_ERR(req);
+			break;
+		}
+
+		more = len < iov_iter_count(to);
 
-		ret = striped_read(inode, off, ret, pages, num_pages,
-				   page_off, checkeof);
-		if (ret > 0) {
-			iov_iter_advance(to, ret);
-			off += ret;
+		if (unlikely(to->type & ITER_PIPE)) {
+			ret = iov_iter_get_pages_alloc(to, &pages, len,
+						       &page_off);
+			if (ret <= 0) {
+				ceph_osdc_put_request(req);
+				ret = -ENOMEM;
+				break;
+			}
+			num_pages = DIV_ROUND_UP(ret + page_off, PAGE_SIZE);
+			if (ret < len) {
+				len = ret;
+				osd_req_op_extent_update(req, 0, len);
+				more = false;
+			}
 		} else {
-			iov_iter_advance(to, 0);
+			num_pages = calc_pages_for(off, len);
+			page_off = off & ~PAGE_MASK;
+			pages = ceph_alloc_page_vector(num_pages, GFP_KERNEL);
+			if (IS_ERR(pages)) {
+				ceph_osdc_put_request(req);
+				ret = PTR_ERR(pages);
+				break;
+			}
 		}
-		ceph_put_page_vector(pages, num_pages, false);
-	} else {
-		num_pages = calc_pages_for(off, len);
-		pages = ceph_alloc_page_vector(num_pages, GFP_KERNEL);
-		if (IS_ERR(pages))
-			return PTR_ERR(pages);
-
-		ret = striped_read(inode, off, len, pages, num_pages,
-				   (off & ~PAGE_MASK), checkeof);
-		if (ret > 0) {
-			int l, k = 0;
-			size_t left = ret;
-
-			while (left) {
-				size_t page_off = off & ~PAGE_MASK;
-				size_t copy = min_t(size_t, left,
-						    PAGE_SIZE - page_off);
-				l = copy_page_to_iter(pages[k++], page_off,
-						      copy, to);
-				off += l;
-				left -= l;
-				if (l < copy)
+
+		osd_req_op_extent_osd_data_pages(req, 0, pages, len, page_off,
+						 false, false);
+		ret = ceph_osdc_start_request(osdc, req, false);
+		if (!ret)
+			ret = ceph_osdc_wait_request(osdc, req);
+		ceph_osdc_put_request(req);
+
+		i_size = i_size_read(inode);
+		dout("sync_read %llu~%llu got %zd i_size %llu%s\n",
+		     off, len, ret, i_size, (more ? " MORE" : ""));
+
+		if (ret == -ENOENT)
+			ret = 0;
+		if (ret >= 0 && ret < len && (off + ret < i_size)) {
+			int zlen = min(len - ret, i_size - off - ret);
+			int zoff = page_off + ret;
+			dout("sync_read zero gap %llu~%llu\n",
+                             off + ret, off + ret + zlen);
+			ceph_zero_page_vector_range(zoff, zlen, pages);
+			ret += zlen;
+		}
+
+		if (unlikely(to->type & ITER_PIPE)) {
+			if (ret > 0) {
+				iov_iter_advance(to, ret);
+				off += ret;
+			} else {
+				iov_iter_advance(to, 0);
+			}
+			ceph_put_page_vector(pages, num_pages, false);
+		} else {
+			int idx = 0;
+			size_t left = ret > 0 ? ret : 0;
+			while (left > 0) {
+				size_t len, copied;
+				page_off = off & ~PAGE_MASK;
+				len = min_t(size_t, left, PAGE_SIZE - page_off);
+				copied = copy_page_to_iter(pages[idx++],
+							   page_off, len, to);
+				off += copied;
+				left -= copied;
+				if (copied < len) {
+					ret = -EFAULT;
 					break;
+				}
 			}
+			ceph_release_page_vector(pages, num_pages);
 		}
-		ceph_release_page_vector(pages, num_pages);
+
+		if (ret <= 0 || off >= i_size || !more)
+			break;
 	}
 
 	if (off > iocb->ki_pos) {
+		if (ret >= 0 &&
+		    iov_iter_count(to) > 0 && off >= i_size_read(inode))
+			*retry_op = CHECK_EOF;
 		ret = off - iocb->ki_pos;
 		iocb->ki_pos = off;
 	}
 
-	dout("sync_read result %zd\n", ret);
+	dout("sync_read result %zd retry_op %d\n", ret, *retry_op);
 	return ret;
 }