[v4,2/2] ceph: wait the first reply of inflight async unlink

diff --git a/fs/ceph/dir.c b/fs/ceph/dir.c
index eae417d71136..01e7facef9b2 100644
--- a/fs/ceph/dir.c
+++ b/fs/ceph/dir.c
@@ -856,6 +856,10 @@  static int ceph_mknod(struct user_namespace *mnt_userns, struct inode *dir,
 	if (ceph_snap(dir) != CEPH_NOSNAP)
 		return -EROFS;
 
+	err = ceph_wait_on_conflict_unlink(dentry);
+	if (err)
+		return err;
+
 	if (ceph_quota_is_max_files_exceeded(dir)) {
 		err = -EDQUOT;
 		goto out;
@@ -918,6 +922,10 @@  static int ceph_symlink(struct user_namespace *mnt_userns, struct inode *dir,
 	if (ceph_snap(dir) != CEPH_NOSNAP)
 		return -EROFS;
 
+	err = ceph_wait_on_conflict_unlink(dentry);
+	if (err)
+		return err;
+
 	if (ceph_quota_is_max_files_exceeded(dir)) {
 		err = -EDQUOT;
 		goto out;
@@ -968,9 +976,13 @@  static int ceph_mkdir(struct user_namespace *mnt_userns, struct inode *dir,
 	struct ceph_mds_client *mdsc = ceph_sb_to_mdsc(dir->i_sb);
 	struct ceph_mds_request *req;
 	struct ceph_acl_sec_ctx as_ctx = {};
-	int err = -EROFS;
+	int err;
 	int op;
 
+	err = ceph_wait_on_conflict_unlink(dentry);
+	if (err)
+		return err;
+
 	if (ceph_snap(dir) == CEPH_SNAPDIR) {
 		/* mkdir .snap/foo is a MKSNAP */
 		op = CEPH_MDS_OP_MKSNAP;
@@ -980,6 +992,7 @@  static int ceph_mkdir(struct user_namespace *mnt_userns, struct inode *dir,
 		dout("mkdir dir %p dn %p mode 0%ho\n", dir, dentry, mode);
 		op = CEPH_MDS_OP_MKDIR;
 	} else {
+		err = -EROFS;
 		goto out;
 	}
 
@@ -1037,6 +1050,10 @@  static int ceph_link(struct dentry *old_dentry, struct inode *dir,
 	struct ceph_mds_request *req;
 	int err;
 
+	err = ceph_wait_on_conflict_unlink(dentry);
+	if (err)
+		return err;
+
 	if (ceph_snap(dir) != CEPH_NOSNAP)
 		return -EROFS;
 
@@ -1071,9 +1088,27 @@  static int ceph_link(struct dentry *old_dentry, struct inode *dir,
 static void ceph_async_unlink_cb(struct ceph_mds_client *mdsc,
 				 struct ceph_mds_request *req)
 {
+	struct dentry *dentry = req->r_dentry;
+	struct ceph_fs_client *fsc = ceph_sb_to_client(dentry->d_sb);
+	struct ceph_dentry_info *di = ceph_dentry(dentry);
 	int result = req->r_err ? req->r_err :
 			le32_to_cpu(req->r_reply_info.head->result);
 
+	if (!test_bit(CEPH_DENTRY_ASYNC_UNLINK_BIT, &di->flags))
+		pr_warn("%s dentry %p:%pd async unlink bit is not set\n",
+			__func__, dentry, dentry);
+
+	spin_lock(&fsc->async_unlink_conflict_lock);
+	hash_del_rcu(&di->hnode);
+	spin_unlock(&fsc->async_unlink_conflict_lock);
+
+	spin_lock(&dentry->d_lock);
+	di->flags &= ~CEPH_DENTRY_ASYNC_UNLINK;
+	wake_up_bit(&di->flags, CEPH_DENTRY_ASYNC_UNLINK_BIT);
+	spin_unlock(&dentry->d_lock);
+
+	synchronize_rcu();
+
 	if (result == -EJUKEBOX)
 		goto out;
 
@@ -1081,7 +1116,7 @@  static void ceph_async_unlink_cb(struct ceph_mds_client *mdsc,
 	if (result) {
 		int pathlen = 0;
 		u64 base = 0;
-		char *path = ceph_mdsc_build_path(req->r_dentry, &pathlen,
+		char *path = ceph_mdsc_build_path(dentry, &pathlen,
 						  &base, 0);
 
 		/* mark error on parent + clear complete */
@@ -1089,13 +1124,13 @@  static void ceph_async_unlink_cb(struct ceph_mds_client *mdsc,
 		ceph_dir_clear_complete(req->r_parent);
 
 		/* drop the dentry -- we don't know its status */
-		if (!d_unhashed(req->r_dentry))
-			d_drop(req->r_dentry);
+		if (!d_unhashed(dentry))
+			d_drop(dentry);
 
 		/* mark inode itself for an error (since metadata is bogus) */
 		mapping_set_error(req->r_old_inode->i_mapping, result);
 
-		pr_warn("ceph: async unlink failure path=(%llx)%s result=%d!\n",
+		pr_warn("async unlink failure path=(%llx)%s result=%d!\n",
 			base, IS_ERR(path) ? "<<bad>>" : path, result);
 		ceph_mdsc_free_path(path, pathlen);
 	}
@@ -1180,6 +1215,8 @@  static int ceph_unlink(struct inode *dir, struct dentry *dentry)
 
 	if (try_async && op == CEPH_MDS_OP_UNLINK &&
 	    (req->r_dir_caps = get_caps_for_async_unlink(dir, dentry))) {
+		struct ceph_dentry_info *di = ceph_dentry(dentry);
+
 		dout("async unlink on %llu/%.*s caps=%s", ceph_ino(dir),
 		     dentry->d_name.len, dentry->d_name.name,
 		     ceph_cap_string(req->r_dir_caps));
@@ -1187,6 +1224,16 @@  static int ceph_unlink(struct inode *dir, struct dentry *dentry)
 		req->r_callback = ceph_async_unlink_cb;
 		req->r_old_inode = d_inode(dentry);
 		ihold(req->r_old_inode);
+
+		spin_lock(&dentry->d_lock);
+		di->flags |= CEPH_DENTRY_ASYNC_UNLINK;
+		spin_unlock(&dentry->d_lock);
+
+		spin_lock(&fsc->async_unlink_conflict_lock);
+		hash_add_rcu(fsc->async_unlink_conflict, &di->hnode,
+			     dentry->d_name.hash);
+		spin_unlock(&fsc->async_unlink_conflict_lock);
+
 		err = ceph_mdsc_submit_request(mdsc, dir, req);
 		if (!err) {
 			/*
@@ -1198,6 +1245,15 @@  static int ceph_unlink(struct inode *dir, struct dentry *dentry)
 		} else if (err == -EJUKEBOX) {
 			try_async = false;
 			ceph_mdsc_put_request(req);
+
+			spin_lock(&dentry->d_lock);
+			di->flags &= ~CEPH_DENTRY_ASYNC_UNLINK;
+			spin_unlock(&dentry->d_lock);
+
+			spin_lock(&fsc->async_unlink_conflict_lock);
+			hash_del_rcu(&di->hnode);
+			spin_unlock(&fsc->async_unlink_conflict_lock);
+
 			goto retry;
 		}
 	} else {
@@ -1237,6 +1293,10 @@  static int ceph_rename(struct user_namespace *mnt_userns, struct inode *old_dir,
 	    (!ceph_quota_is_same_realm(old_dir, new_dir)))
 		return -EXDEV;
 
+	err = ceph_wait_on_conflict_unlink(new_dentry);
+	if (err)
+		return err;
+
 	dout("rename dir %p dentry %p to dir %p dentry %p\n",
 	     old_dir, old_dentry, new_dir, new_dentry);
 	req = ceph_mdsc_create_request(mdsc, op, USE_AUTH_MDS);
diff --git a/fs/ceph/file.c b/fs/ceph/file.c
index 8c8226c0feac..f039e799f5f4 100644
--- a/fs/ceph/file.c
+++ b/fs/ceph/file.c
@@ -740,6 +740,10 @@  int ceph_atomic_open(struct inode *dir, struct dentry *dentry,
 	if (dentry->d_name.len > NAME_MAX)
 		return -ENAMETOOLONG;
 
+	err = ceph_wait_on_conflict_unlink(dentry);
+	if (err)
+		return err;
+
 	if (flags & O_CREAT) {
 		if (ceph_quota_is_max_files_exceeded(dir))
 			return -EDQUOT;
diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c
index e8c87dea0551..ffe52b7c6cbc 100644
--- a/fs/ceph/mds_client.c
+++ b/fs/ceph/mds_client.c
@@ -655,6 +655,79 @@  static void destroy_reply_info(struct ceph_mds_reply_info_parsed *info)
 	free_pages((unsigned long)info->dir_entries, get_order(info->dir_buf_size));
 }
 
+/*
+ * In async unlink case the kclient won't wait for the first reply
+ * from MDS and just drop all the links and unhash the dentry and then
+ * succeeds immediately.
+ *
+ * For any new create/link/rename,etc requests followed by using the
+ * same file names we must wait for the first reply of the inflight
+ * unlink request, or the MDS possibly will fail these following
+ * requests with -EEXIST if the inflight async unlink request was
+ * delayed for some reasons.
+ *
+ * And the worst case is that for the none async openc request it will
+ * successfully open the file if the CDentry hasn't been unlinked yet,
+ * but later the previous delayed async unlink request will remove the
+ * CDenty. That means the just created file is possiblly deleted later
+ * by accident.
+ *
+ * We need to wait for the inflight async unlink requests to finish
+ * when creating new files/directories by using the same file names.
+ */
+int ceph_wait_on_conflict_unlink(struct dentry *dentry)
+{
+	struct ceph_fs_client *fsc = ceph_sb_to_client(dentry->d_sb);
+	struct dentry *pdentry = dentry->d_parent;
+	struct dentry *udentry, *found = NULL;
+	struct ceph_dentry_info *di;
+	struct qstr dname;
+	u32 hash = dentry->d_name.hash;
+	int err;
+
+	dname.name = dentry->d_name.name;
+	dname.len = dentry->d_name.len;
+
+	rcu_read_lock();
+	hash_for_each_possible_rcu(fsc->async_unlink_conflict, di,
+				   hnode, hash) {
+		udentry = di->dentry;
+
+		spin_lock(&udentry->d_lock);
+		if (udentry->d_name.hash != hash)
+			goto next;
+		if (unlikely(udentry->d_parent != pdentry))
+			goto next;
+		if (!hash_hashed(&di->hnode))
+			goto next;
+
+		if (!test_bit(CEPH_DENTRY_ASYNC_UNLINK_BIT, &di->flags))
+			pr_warn("%s dentry %p:%pd async unlink bit is not set\n",
+				__func__, dentry, dentry);
+
+		if (d_compare(pdentry, udentry, &dname))
+			goto next;
+
+		spin_unlock(&udentry->d_lock);
+		found = dget(udentry);
+		break;
+next:
+		spin_unlock(&udentry->d_lock);
+	}
+	rcu_read_unlock();
+
+	if (likely(!found))
+		return 0;
+
+	dout("%s dentry %p:%pd conflict with old %p:%pd\n", __func__,
+	     dentry, dentry, found, found);
+
+	err = wait_on_bit(&di->flags, CEPH_DENTRY_ASYNC_UNLINK_BIT,
+			  TASK_KILLABLE);
+	dput(found);
+	return err;
+}
+
 
 /*
  * sessions
diff --git a/fs/ceph/mds_client.h b/fs/ceph/mds_client.h
index 33497846e47e..d1ae679c52c3 100644
--- a/fs/ceph/mds_client.h
+++ b/fs/ceph/mds_client.h
@@ -582,6 +582,7 @@  static inline int ceph_wait_on_async_create(struct inode *inode)
 			   TASK_INTERRUPTIBLE);
 }
 
+extern int ceph_wait_on_conflict_unlink(struct dentry *dentry);
 extern u64 ceph_get_deleg_ino(struct ceph_mds_session *session);
 extern int ceph_restore_deleg_ino(struct ceph_mds_session *session, u64 ino);
 #endif
diff --git a/fs/ceph/super.c b/fs/ceph/super.c
index b73b4f75462c..6542b71f8627 100644
--- a/fs/ceph/super.c
+++ b/fs/ceph/super.c
@@ -816,6 +816,9 @@  static struct ceph_fs_client *create_fs_client(struct ceph_mount_options *fsopt,
 	if (!fsc->cap_wq)
 		goto fail_inode_wq;
 
+	hash_init(fsc->async_unlink_conflict);
+	spin_lock_init(&fsc->async_unlink_conflict_lock);
+
 	spin_lock(&ceph_fsc_lock);
 	list_add_tail(&fsc->metric_wakeup, &ceph_fsc_list);
 	spin_unlock(&ceph_fsc_lock);
diff --git a/fs/ceph/super.h b/fs/ceph/super.h
index 506d52633627..251e726ec628 100644
--- a/fs/ceph/super.h
+++ b/fs/ceph/super.h
@@ -19,6 +19,7 @@ 
 #include <linux/security.h>
 #include <linux/netfs.h>
 #include <linux/fscache.h>
+#include <linux/hashtable.h>
 
 #include <linux/ceph/libceph.h>
 
@@ -99,6 +100,8 @@  struct ceph_mount_options {
 	char *mon_addr;
 };
 
+#define CEPH_ASYNC_CREATE_CONFLICT_BITS 8
+
 struct ceph_fs_client {
 	struct super_block *sb;
 
@@ -124,6 +127,9 @@  struct ceph_fs_client {
 	struct workqueue_struct *inode_wq;
 	struct workqueue_struct *cap_wq;
 
+	DECLARE_HASHTABLE(async_unlink_conflict, CEPH_ASYNC_CREATE_CONFLICT_BITS);
+	spinlock_t async_unlink_conflict_lock;
+
 #ifdef CONFIG_DEBUG_FS
 	struct dentry *debugfs_dentry_lru, *debugfs_caps;
 	struct dentry *debugfs_congestion_kb;
@@ -281,7 +287,8 @@  struct ceph_dentry_info {
 	struct dentry *dentry;
 	struct ceph_mds_session *lease_session;
 	struct list_head lease_list;
-	unsigned flags;
+	struct hlist_node hnode;
+	unsigned long flags;
 	int lease_shared_gen;
 	u32 lease_gen;
 	u32 lease_seq;
@@ -290,10 +297,12 @@  struct ceph_dentry_info {
 	u64 offset;
 };
 
-#define CEPH_DENTRY_REFERENCED		1
-#define CEPH_DENTRY_LEASE_LIST		2
-#define CEPH_DENTRY_SHRINK_LIST		4
-#define CEPH_DENTRY_PRIMARY_LINK	8
+#define CEPH_DENTRY_REFERENCED		(1 << 0)
+#define CEPH_DENTRY_LEASE_LIST		(1 << 1)
+#define CEPH_DENTRY_SHRINK_LIST		(1 << 2)
+#define CEPH_DENTRY_PRIMARY_LINK	(1 << 3)
+#define CEPH_DENTRY_ASYNC_UNLINK_BIT	(4)
+#define CEPH_DENTRY_ASYNC_UNLINK	(1 << CEPH_DENTRY_ASYNC_UNLINK_BIT)
 
 struct ceph_inode_xattrs_info {
 	/*