[RFC PATCH 2/3] ceph: parallelize all copy-from requests in copy_file_range

[Luis Henriques <lhenriques@suse.com>]

Right now the copy_file_range syscall serializes all the OSDs 'copy-from'
operations, waiting for each request to complete before sending the next
one.  This patch modifies copy_file_range so that all the 'copy-from'
operations are sent in bulk and waits for its completion at the end.  This
will allow significant speed-ups, specially when sending requests for
different target OSDs.

Signed-off-by: Luis Henriques <lhenriques@suse.com>
---
 fs/ceph/file.c                  | 38 +++++++++++++++++++++++++++++++--
 include/linux/ceph/osd_client.h |  2 ++
 net/ceph/osd_client.c           |  1 +
 3 files changed, 39 insertions(+), 2 deletions(-)

diff --git a/fs/ceph/file.c b/fs/ceph/file.c
index 1e6cdf2dfe90..5d8f0ba11719 100644
--- a/fs/ceph/file.c
+++ b/fs/ceph/file.c
@@ -1931,6 +1931,28 @@ static int is_file_size_ok(struct inode *src_inode, struct inode *dst_inode,
 	return 0;
 }
 
+static int wait_copy_from_reqs(struct list_head *osd_reqs)
+{
+	struct ceph_osd_request *req;
+	int ret = 0, err;
+
+	while (!list_empty(osd_reqs)) {
+		req = list_first_entry(osd_reqs,
+				       struct ceph_osd_request,
+				       r_copy_item);
+		list_del_init(&req->r_copy_item);
+		err = ceph_osdc_wait_request(req->r_osdc, req);
+		if (err) {
+			if (!ret)
+				ret = err;
+			dout("copy request failed (err=%d)\n", err);
+		}
+		ceph_osdc_put_request(req);
+	}
+
+	return ret;
+}
+
 static ssize_t __ceph_copy_file_range(struct file *src_file, loff_t src_off,
 				      struct file *dst_file, loff_t dst_off,
 				      size_t len, unsigned int flags)
@@ -1943,12 +1965,14 @@ static ssize_t __ceph_copy_file_range(struct file *src_file, loff_t src_off,
 	struct ceph_fs_client *src_fsc = ceph_inode_to_client(src_inode);
 	struct ceph_object_locator src_oloc, dst_oloc;
 	struct ceph_object_id src_oid, dst_oid;
+	struct ceph_osd_request *req;
 	loff_t endoff = 0, size;
 	ssize_t ret = -EIO;
 	u64 src_objnum, dst_objnum, src_objoff, dst_objoff;
 	u32 src_objlen, dst_objlen, object_size;
 	int src_got = 0, dst_got = 0, err, dirty;
 	bool do_final_copy = false;
+	LIST_HEAD(osd_reqs);
 
 	if (src_inode->i_sb != dst_inode->i_sb) {
 		struct ceph_fs_client *dst_fsc = ceph_inode_to_client(dst_inode);
@@ -2097,7 +2121,7 @@ static ssize_t __ceph_copy_file_range(struct file *src_file, loff_t src_off,
 		ceph_oid_printf(&dst_oid, "%llx.%08llx",
 				dst_ci->i_vino.ino, dst_objnum);
 		/* Do an object remote copy */
-		err = ceph_osdc_copy_from(
+		req = ceph_osdc_copy_from_nowait(
 			&src_fsc->client->osdc,
 			src_ci->i_vino.snap, 0,
 			&src_oid, &src_oloc,
@@ -2108,7 +2132,8 @@ static ssize_t __ceph_copy_file_range(struct file *src_file, loff_t src_off,
 			CEPH_OSD_OP_FLAG_FADVISE_DONTNEED,
 			dst_ci->i_truncate_seq, dst_ci->i_truncate_size,
 			CEPH_OSD_COPY_FROM_FLAG_TRUNCATE_SEQ);
-		if (err) {
+		if (IS_ERR(req)) {
+			err = PTR_ERR(req);
 			if (err == -EOPNOTSUPP) {
 				src_fsc->have_copy_from2 = false;
 				pr_notice("OSDs don't support 'copy-from2'; "
@@ -2117,14 +2142,23 @@ static ssize_t __ceph_copy_file_range(struct file *src_file, loff_t src_off,
 			dout("ceph_osdc_copy_from returned %d\n", err);
 			if (!ret)
 				ret = err;
+			/* wait for all queued requests */
+			wait_copy_from_reqs(&osd_reqs);
 			goto out_caps;
 		}
+		list_add(&req->r_copy_item, &osd_reqs);
 		len -= object_size;
 		src_off += object_size;
 		dst_off += object_size;
 		ret += object_size;
 	}
 
+	err = wait_copy_from_reqs(&osd_reqs);
+	if (err) {
+		if (!ret)
+			ret = err;
+		goto out_caps;
+	}
 	if (len)
 		/* We still need one final local copy */
 		do_final_copy = true;
diff --git a/include/linux/ceph/osd_client.h b/include/linux/ceph/osd_client.h
index 7916a178d137..2b4a14bc6154 100644
--- a/include/linux/ceph/osd_client.h
+++ b/include/linux/ceph/osd_client.h
@@ -210,6 +210,8 @@ struct ceph_osd_request {
 	u64 r_data_offset;                    /* ditto */
 	bool r_linger;                        /* don't resend on failure */
 
+	struct list_head r_copy_item;         /* used for copy-from operations */
+
 	/* internal */
 	unsigned long r_stamp;                /* jiffies, send or check time */
 	unsigned long r_start_stamp;          /* jiffies */
diff --git a/net/ceph/osd_client.c b/net/ceph/osd_client.c
index 7f984532f37c..16f38c3d606e 100644
--- a/net/ceph/osd_client.c
+++ b/net/ceph/osd_client.c
@@ -531,6 +531,7 @@ static void request_init(struct ceph_osd_request *req)
 	RB_CLEAR_NODE(&req->r_node);
 	RB_CLEAR_NODE(&req->r_mc_node);
 	INIT_LIST_HEAD(&req->r_private_item);
+	INIT_LIST_HEAD(&req->r_copy_item);
 
 	target_init(&req->r_t);
 }