ceph: make seeky readdir more efficient
Current cephfs client uses string to indicate start position of
readdir. The string is last entry of previous readdir reply.
This approach does not work for seeky readdir because we can
not easily convert the new postion to a string. For seeky readdir,
mds needs to return dentries from the beginning. Client keeps
retrying if the reply does not contain the dentry it wants.
In current version of ceph, mds sorts CDentry in its cache in
hash order. Client also uses dentry hash to compose dir postion.
For seeky readdir, if client passes the hash part of dir postion
to mds. mds can avoid replying useless dentries.
Signed-off-by: "Yan, Zheng" <zyan@redhat.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
diff --git a/fs/ceph/inode.c b/fs/ceph/inode.c
index d3119fe..dcce79b 100644
--- a/fs/ceph/inode.c
+++ b/fs/ceph/inode.c
@@ -1482,10 +1482,17 @@
if (test_bit(CEPH_MDS_R_ABORTED, &req->r_req_flags))
return readdir_prepopulate_inodes_only(req, session);
- if (rinfo->hash_order && req->r_path2) {
- last_hash = ceph_str_hash(ci->i_dir_layout.dl_dir_hash,
- req->r_path2, strlen(req->r_path2));
- last_hash = ceph_frag_value(last_hash);
+ if (rinfo->hash_order) {
+ if (req->r_path2) {
+ last_hash = ceph_str_hash(ci->i_dir_layout.dl_dir_hash,
+ req->r_path2,
+ strlen(req->r_path2));
+ last_hash = ceph_frag_value(last_hash);
+ } else if (rinfo->offset_hash) {
+ /* mds understands offset_hash */
+ WARN_ON_ONCE(req->r_readdir_offset != 2);
+ last_hash = le32_to_cpu(rhead->args.readdir.offset_hash);
+ }
}
if (rinfo->dir_dir &&
@@ -1510,7 +1517,7 @@
}
if (ceph_frag_is_leftmost(frag) && req->r_readdir_offset == 2 &&
- !(rinfo->hash_order && req->r_path2)) {
+ !(rinfo->hash_order && last_hash)) {
/* note dir version at start of readdir so we can tell
* if any dentries get dropped */
req->r_dir_release_cnt = atomic64_read(&ci->i_release_count);