[RFC PATCH 9/9] ceph: attempt to do async create when possible

[Jeff Layton <jlayton@kernel.org>]

With the Octopus release, the MDS will hand out directoy create caps.
If we have Fxc caps on the directory, and complete directory information
or a known negative dentry, then we can return without waiting on the
reply, allowing the open() call to return very quickly to userland.

We use the normal ceph_fill_inode() routine to fill in the inode, so we
have to gin up some reply inode information with what we'd expect a
newly-created inode to have. The client assumes that it has a full set
of caps on the new inode, and that the MDS will revoke them when there
is conflicting access.

This functionality is gated on the enable_async_dirops module option,
along with async unlinks, and on the server supporting the Octopus
CephFS feature bit.

Signed-off-by: Jeff Layton <jlayton@kernel.org>
---
 fs/ceph/caps.c               |   7 +-
 fs/ceph/file.c               | 178 +++++++++++++++++++++++++++++++++--
 fs/ceph/mds_client.c         |  12 ++-
 fs/ceph/mds_client.h         |   3 +-
 fs/ceph/super.h              |   2 +
 include/linux/ceph/ceph_fs.h |   8 +-
 6 files changed, 191 insertions(+), 19 deletions(-)

diff --git a/fs/ceph/caps.c b/fs/ceph/caps.c
index b96fb1378479..21a8a2ddc94b 100644
--- a/fs/ceph/caps.c
+++ b/fs/ceph/caps.c
@@ -654,6 +654,10 @@ void ceph_add_cap(struct inode *inode,
 		session->s_nr_caps++;
 		spin_unlock(&session->s_cap_lock);
 	} else {
+		/* Did an async create race with the reply? */
+		if (cap_id == CEPH_CAP_ID_TBD && cap->issued == issued)
+			return;
+
 		spin_lock(&session->s_cap_lock);
 		list_move_tail(&cap->session_caps, &session->s_caps);
 		spin_unlock(&session->s_cap_lock);
@@ -672,7 +676,8 @@ void ceph_add_cap(struct inode *inode,
 		 */
 		if (ceph_seq_cmp(seq, cap->seq) <= 0) {
 			WARN_ON(cap != ci->i_auth_cap);
-			WARN_ON(cap->cap_id != cap_id);
+			WARN_ON(cap_id != CEPH_CAP_ID_TBD &&
+				cap->cap_id != cap_id);
 			seq = cap->seq;
 			mseq = cap->mseq;
 			issued |= cap->issued;
diff --git a/fs/ceph/file.c b/fs/ceph/file.c
index d4d7a277faf1..706abd71b731 100644
--- a/fs/ceph/file.c
+++ b/fs/ceph/file.c
@@ -450,6 +450,141 @@ copy_file_layout(struct inode *dst, struct inode *src)
 	spin_unlock(&cdst->i_ceph_lock);
 }
 
+static bool get_caps_for_async_create(struct inode *dir, struct dentry *dentry)
+{
+	struct ceph_inode_info *ci = ceph_inode(dir);
+	int ret, want, got;
+
+	/*
+	 * We can do an async create if we either have a valid negative dentry
+	 * or the complete contents of the directory. Do a quick check without
+	 * cap refs.
+	 */
+	if ((d_in_lookup(dentry) && !__ceph_dir_is_complete(ci)) ||
+	    !ceph_file_layout_is_valid(&ci->i_layout))
+		return false;
+
+	/* Try to get caps */
+	want = CEPH_CAP_FILE_EXCL | CEPH_CAP_DIR_CREATE;
+	ret = ceph_try_get_caps(dir, 0, want, true, &got);
+	dout("Fx on %p ret=%d got=%d\n", dir, ret, got);
+	if (ret != 1)
+		return false;
+	if (got != want) {
+		ceph_put_cap_refs(ci, got);
+		return false;
+	}
+
+	/* Check again, now that we hold cap refs */
+	if ((d_in_lookup(dentry) && !__ceph_dir_is_complete(ci)) ||
+	    !ceph_file_layout_is_valid(&ci->i_layout)) {
+		ceph_put_cap_refs(ci, got);
+		return false;
+	}
+
+	return true;
+}
+
+static void ceph_async_create_cb(struct ceph_mds_client *mdsc,
+                                 struct ceph_mds_request *req)
+{
+	/* If we never sent anything then nothing to clean up */
+	if (req->r_err == -ECHILD)
+		goto out;
+
+	mapping_set_error(req->r_parent->i_mapping, req->r_err);
+
+	if (req->r_target_inode) {
+		u64 ino = ceph_vino(req->r_target_inode).ino;
+
+		if (req->r_deleg_ino != ino)
+			pr_warn("%s: inode number mismatch! err=%d deleg_ino=0x%lx target=0x%llx\n",
+				__func__, req->r_err, req->r_deleg_ino, ino);
+		mapping_set_error(req->r_target_inode->i_mapping, req->r_err);
+	} else {
+		pr_warn("%s: no req->r_target_inode for 0x%lx\n", __func__,
+			req->r_deleg_ino);
+	}
+out:
+	ceph_put_cap_refs(ceph_inode(req->r_parent),
+			  CEPH_CAP_FILE_EXCL | CEPH_CAP_DIR_CREATE);
+}
+
+static int ceph_finish_async_open(struct inode *dir, struct dentry *dentry,
+				  struct file *file, umode_t mode,
+				  struct ceph_mds_request *req,
+				  struct ceph_acl_sec_ctx *as_ctx)
+{
+	int ret;
+	struct ceph_mds_reply_inode in = { };
+	struct ceph_mds_reply_info_in iinfo = { .in = &in };
+	struct ceph_inode_info *ci = ceph_inode(dir);
+	struct inode *inode;
+	struct timespec64 now;
+	struct ceph_vino vino = { .ino = req->r_deleg_ino,
+				  .snap = CEPH_NOSNAP };
+
+	ktime_get_real_ts64(&now);
+
+	inode = ceph_get_inode(dentry->d_sb, vino);
+	if (IS_ERR(inode))
+		return PTR_ERR(inode);
+
+	/* If we can't get a buffer, just carry on */
+	iinfo.xattr_data = kzalloc(4, GFP_NOFS);
+	if (iinfo.xattr_data)
+		iinfo.xattr_len = 4;
+
+	iinfo.inline_version = CEPH_INLINE_NONE;
+	iinfo.change_attr = 1;
+	ceph_encode_timespec64(&iinfo.btime, &now);
+
+	in.ino = cpu_to_le64(vino.ino);
+	in.snapid = cpu_to_le64(CEPH_NOSNAP);
+	in.version = cpu_to_le64(1);	// ???
+	in.cap.caps = in.cap.wanted = cpu_to_le32(CEPH_CAP_ALL_FILE);
+	in.cap.cap_id = cpu_to_le64(CEPH_CAP_ID_TBD);
+	in.cap.realm = cpu_to_le64(ci->i_snap_realm->ino);
+	in.cap.flags = CEPH_CAP_FLAG_AUTH;
+	in.ctime = in.mtime = in.atime = iinfo.btime;
+	in.mode = cpu_to_le32((u32)mode);
+	in.truncate_seq = cpu_to_le32(1);
+	in.truncate_size = cpu_to_le64(ci->i_truncate_size);
+	in.max_size = cpu_to_le64(ci->i_max_size);
+	in.xattr_version = cpu_to_le64(1);
+	in.uid = cpu_to_le32(from_kuid(&init_user_ns, current_fsuid()));
+	in.gid = cpu_to_le32(from_kgid(&init_user_ns, current_fsgid()));
+	in.nlink = cpu_to_le32(1);
+
+	ceph_file_layout_to_legacy(&ci->i_layout, &in.layout);
+
+	ret = ceph_fill_inode(inode, NULL, &iinfo, NULL, req->r_session,
+			      req->r_fmode, NULL);
+	if (ret) {
+		dout("%s failed to fill inode: %d\n", __func__, ret);
+		if (inode->i_state & I_NEW)
+			discard_new_inode(inode);
+	} else {
+		struct dentry *dn;
+
+		dout("%s d_adding new inode 0x%llx to 0x%lx/%s\n", __func__,
+			vino.ino, dir->i_ino, dentry->d_name.name);
+		ceph_dir_clear_ordered(dir);
+		ceph_init_inode_acls(inode, as_ctx);
+		if (inode->i_state & I_NEW)
+			unlock_new_inode(inode);
+		if (d_in_lookup(dentry) || d_really_is_negative(dentry)) {
+			if (!d_unhashed(dentry))
+				d_drop(dentry);
+			dn = d_splice_alias(inode, dentry);
+			WARN_ON_ONCE(dn && dn != dentry);
+		}
+		file->f_mode |= FMODE_CREATED;
+		ret = finish_open(file, dentry, ceph_open);
+	}
+	return ret;
+}
+
 /*
  * Do a lookup + open with a single request.  If we get a non-existent
  * file or symlink, return 1 so the VFS can retry.
@@ -462,6 +597,7 @@ int ceph_atomic_open(struct inode *dir, struct dentry *dentry,
 	struct ceph_mds_request *req;
 	struct dentry *dn;
 	struct ceph_acl_sec_ctx as_ctx = {};
+	bool try_async = enable_async_dirops;
 	int mask;
 	int err;
 
@@ -486,6 +622,7 @@ int ceph_atomic_open(struct inode *dir, struct dentry *dentry,
 		return -ENOENT;
 	}
 
+retry:
 	/* do the open */
 	req = prepare_open_request(dir->i_sb, flags, mode);
 	if (IS_ERR(req)) {
@@ -494,6 +631,12 @@ int ceph_atomic_open(struct inode *dir, struct dentry *dentry,
 	}
 	req->r_dentry = dget(dentry);
 	req->r_num_caps = 2;
+	mask = CEPH_STAT_CAP_INODE | CEPH_CAP_AUTH_SHARED;
+	if (ceph_security_xattr_wanted(dir))
+		mask |= CEPH_CAP_XATTR_SHARED;
+	req->r_args.open.mask = cpu_to_le32(mask);
+	req->r_parent = dir;
+
 	if (flags & O_CREAT) {
 		req->r_dentry_drop = CEPH_CAP_FILE_SHARED | CEPH_CAP_AUTH_EXCL;
 		req->r_dentry_unless = CEPH_CAP_FILE_EXCL;
@@ -501,21 +644,37 @@ int ceph_atomic_open(struct inode *dir, struct dentry *dentry,
 			req->r_pagelist = as_ctx.pagelist;
 			as_ctx.pagelist = NULL;
 		}
+		if (try_async && get_caps_for_async_create(dir, dentry)) {
+			set_bit(CEPH_MDS_R_DELEG_INO, &req->r_req_flags);
+			req->r_callback = ceph_async_create_cb;
+			err = ceph_mdsc_submit_request(mdsc, dir, req);
+			switch (err) {
+			case 0:
+				/* set up inode, dentry and return */
+				err = ceph_finish_async_open(dir, dentry, file,
+							mode, req, &as_ctx);
+				goto out_req;
+			case -ECHILD:
+				/* do a sync create */
+				try_async = false;
+				as_ctx.pagelist = req->r_pagelist;
+				req->r_pagelist = NULL;
+				ceph_mdsc_put_request(req);
+				goto retry;
+			default:
+				/* Hard error, give up */
+				goto out_req;
+			}
+		}
 	}
 
-       mask = CEPH_STAT_CAP_INODE | CEPH_CAP_AUTH_SHARED;
-       if (ceph_security_xattr_wanted(dir))
-               mask |= CEPH_CAP_XATTR_SHARED;
-       req->r_args.open.mask = cpu_to_le32(mask);
-
-	req->r_parent = dir;
 	set_bit(CEPH_MDS_R_PARENT_LOCKED, &req->r_req_flags);
 	err = ceph_mdsc_do_request(mdsc,
 				   (flags & (O_CREAT|O_TRUNC)) ? dir : NULL,
 				   req);
 	err = ceph_handle_snapdir(req, dentry, err);
 	if (err)
-		goto out_req;
+		goto out_fmode;
 
 	if ((flags & O_CREAT) && !req->r_reply_info.head->is_dentry)
 		err = ceph_handle_notrace_create(dir, dentry);
@@ -529,7 +688,7 @@ int ceph_atomic_open(struct inode *dir, struct dentry *dentry,
 		dn = NULL;
 	}
 	if (err)
-		goto out_req;
+		goto out_fmode;
 	if (dn || d_really_is_negative(dentry) || d_is_symlink(dentry)) {
 		/* make vfs retry on splice, ENOENT, or symlink */
 		dout("atomic_open finish_no_open on dn %p\n", dn);
@@ -545,9 +704,10 @@ int ceph_atomic_open(struct inode *dir, struct dentry *dentry,
 		}
 		err = finish_open(file, dentry, ceph_open);
 	}
-out_req:
+out_fmode:
 	if (!req->r_err && req->r_target_inode)
 		ceph_put_fmode(ceph_inode(req->r_target_inode), req->r_fmode);
+out_req:
 	ceph_mdsc_put_request(req);
 out_ctx:
 	ceph_release_acl_sec_ctx(&as_ctx);
diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c
index 9e7492b21b50..c76d6e7f8136 100644
--- a/fs/ceph/mds_client.c
+++ b/fs/ceph/mds_client.c
@@ -2620,14 +2620,16 @@ static int __prepare_send_request(struct ceph_mds_client *mdsc,
 		flags |= CEPH_MDS_FLAG_REPLAY;
 	if (req->r_parent)
 		flags |= CEPH_MDS_FLAG_WANT_DENTRY;
-	rhead->flags = cpu_to_le32(flags);
-	rhead->num_fwd = req->r_num_fwd;
-	rhead->num_retry = req->r_attempts - 1;
-	if (test_bit(CEPH_MDS_R_DELEG_INO, &req->r_req_flags))
+	if (test_bit(CEPH_MDS_R_DELEG_INO, &req->r_req_flags)) {
 		rhead->ino = cpu_to_le64(req->r_deleg_ino);
-	else
+		flags |= CEPH_MDS_FLAG_ASYNC;
+	} else {
 		rhead->ino = 0;
+	}
 
+	rhead->flags = cpu_to_le32(flags);
+	rhead->num_fwd = req->r_num_fwd;
+	rhead->num_retry = req->r_attempts - 1;
 	dout(" r_parent = %p\n", req->r_parent);
 	return 0;
 }
diff --git a/fs/ceph/mds_client.h b/fs/ceph/mds_client.h
index e0b36be7c44f..49e6cd5a07a2 100644
--- a/fs/ceph/mds_client.h
+++ b/fs/ceph/mds_client.h
@@ -39,8 +39,7 @@ enum ceph_feature_type {
 	CEPHFS_FEATURE_REPLY_ENCODING,		\
 	CEPHFS_FEATURE_LAZY_CAP_WANTED,		\
 	CEPHFS_FEATURE_MULTI_RECONNECT,		\
-						\
-	CEPHFS_FEATURE_MAX,			\
+	CEPHFS_FEATURE_OCTOPUS,			\
 }
 #define CEPHFS_FEATURES_CLIENT_REQUIRED {}
 
diff --git a/fs/ceph/super.h b/fs/ceph/super.h
index ec4d66d7c261..33e03fbba888 100644
--- a/fs/ceph/super.h
+++ b/fs/ceph/super.h
@@ -136,6 +136,8 @@ struct ceph_fs_client {
 #endif
 };
 
+/* Special placeholder value for a cap_id during an asynchronous create. */
+#define        CEPH_CAP_ID_TBD         -1ULL
 
 /*
  * File i/o capability.  This tracks shared state with the metadata
diff --git a/include/linux/ceph/ceph_fs.h b/include/linux/ceph/ceph_fs.h
index a099f60feb7b..b127563e21a1 100644
--- a/include/linux/ceph/ceph_fs.h
+++ b/include/linux/ceph/ceph_fs.h
@@ -444,8 +444,9 @@ union ceph_mds_request_args {
 	} __attribute__ ((packed)) lookupino;
 } __attribute__ ((packed));
 
-#define CEPH_MDS_FLAG_REPLAY        1  /* this is a replayed op */
-#define CEPH_MDS_FLAG_WANT_DENTRY   2  /* want dentry in reply */
+#define CEPH_MDS_FLAG_REPLAY		1  /* this is a replayed op */
+#define CEPH_MDS_FLAG_WANT_DENTRY	2  /* want dentry in reply */
+#define CEPH_MDS_FLAG_ASYNC		4  /* request is asynchronous */
 
 struct ceph_mds_request_head {
 	__le64 oldest_client_tid;
@@ -658,6 +659,9 @@ int ceph_flags_to_mode(int flags);
 #define CEPH_CAP_ANY      (CEPH_CAP_ANY_RD | CEPH_CAP_ANY_EXCL | \
 			   CEPH_CAP_ANY_FILE_WR | CEPH_CAP_FILE_LAZYIO | \
 			   CEPH_CAP_PIN)
+#define CEPH_CAP_ALL_FILE (CEPH_CAP_PIN | CEPH_CAP_ANY_SHARED | \
+			   CEPH_CAP_AUTH_EXCL | CEPH_CAP_XATTR_EXCL | \
+			   CEPH_CAP_ANY_FILE_RD | CEPH_CAP_ANY_FILE_WR)
 
 #define CEPH_CAP_LOCKS (CEPH_LOCK_IFILE | CEPH_LOCK_IAUTH | CEPH_LOCK_ILINK | \
 			CEPH_LOCK_IXATTR)
-- 
2.24.1