Merge tag '9p-for-6.9-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/ericvh/v9fs

Pull 9p fix from Eric Van Hensbergen:
 "This contains a single mitigation to help deal with an apparent race
  condition between client and server having to deal with inode number
  collisions"

* tag '9p-for-6.9-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/ericvh/v9fs:
  fs/9p: mitigate inode collisions

4 files changed, 56 insertions, 22 deletions

diff --git a/fs/9p/v9fs.h b/fs/9p/v9fs.h
index 9defa12208f9..1775fcc7f0e8 100644
--- a/fs/9p/v9fs.h
+++ b/fs/9p/v9fs.h
@@ -179,13 +179,14 @@ extern int v9fs_vfs_rename(struct mnt_idmap *idmap,
 			   struct inode *old_dir, struct dentry *old_dentry,
 			   struct inode *new_dir, struct dentry *new_dentry,
 			   unsigned int flags);
-extern struct inode *v9fs_fid_iget(struct super_block *sb, struct p9_fid *fid);
+extern struct inode *v9fs_fid_iget(struct super_block *sb, struct p9_fid *fid,
+						bool new);
 extern const struct inode_operations v9fs_dir_inode_operations_dotl;
 extern const struct inode_operations v9fs_file_inode_operations_dotl;
 extern const struct inode_operations v9fs_symlink_inode_operations_dotl;
 extern const struct netfs_request_ops v9fs_req_ops;
 extern struct inode *v9fs_fid_iget_dotl(struct super_block *sb,
-					struct p9_fid *fid);
+						struct p9_fid *fid, bool new);
 
 /* other default globals */
 #define V9FS_PORT	564
@@ -224,12 +225,12 @@ static inline int v9fs_proto_dotl(struct v9fs_session_info *v9ses)
  */
 static inline struct inode *
 v9fs_get_inode_from_fid(struct v9fs_session_info *v9ses, struct p9_fid *fid,
-			struct super_block *sb)
+			struct super_block *sb, bool new)
 {
 	if (v9fs_proto_dotl(v9ses))
-		return v9fs_fid_iget_dotl(sb, fid);
+		return v9fs_fid_iget_dotl(sb, fid, new);
 	else
-		return v9fs_fid_iget(sb, fid);
+		return v9fs_fid_iget(sb, fid, new);
 }
 
 #endif
diff --git a/fs/9p/vfs_inode.c b/fs/9p/vfs_inode.c
index 47bd77199e20..7a3308d77606 100644
--- a/fs/9p/vfs_inode.c
+++ b/fs/9p/vfs_inode.c
@@ -364,7 +364,8 @@ void v9fs_evict_inode(struct inode *inode)
 		clear_inode(inode);
 }
 
-struct inode *v9fs_fid_iget(struct super_block *sb, struct p9_fid *fid)
+struct inode *
+v9fs_fid_iget(struct super_block *sb, struct p9_fid *fid, bool new)
 {
 	dev_t rdev;
 	int retval;
@@ -376,8 +377,18 @@ struct inode *v9fs_fid_iget(struct super_block *sb, struct p9_fid *fid)
 	inode = iget_locked(sb, QID2INO(&fid->qid));
 	if (unlikely(!inode))
 		return ERR_PTR(-ENOMEM);
-	if (!(inode->i_state & I_NEW))
-		return inode;
+	if (!(inode->i_state & I_NEW)) {
+		if (!new) {
+			goto done;
+		} else {
+			p9_debug(P9_DEBUG_VFS, "WARNING: Inode collision %ld\n",
+						inode->i_ino);
+			iput(inode);
+			remove_inode_hash(inode);
+			inode = iget_locked(sb, QID2INO(&fid->qid));
+			WARN_ON(!(inode->i_state & I_NEW));
+		}
+	}
 
 	/*
 	 * initialize the inode with the stat info
@@ -401,11 +412,11 @@ struct inode *v9fs_fid_iget(struct super_block *sb, struct p9_fid *fid)
 	v9fs_set_netfs_context(inode);
 	v9fs_cache_inode_get_cookie(inode);
 	unlock_new_inode(inode);
+done:
 	return inode;
 error:
 	iget_failed(inode);
 	return ERR_PTR(retval);
-
 }
 
 /**
@@ -437,8 +448,15 @@ static int v9fs_at_to_dotl_flags(int flags)
  */
 static void v9fs_dec_count(struct inode *inode)
 {
-	if (!S_ISDIR(inode->i_mode) || inode->i_nlink > 2)
-		drop_nlink(inode);
+	if (!S_ISDIR(inode->i_mode) || inode->i_nlink > 2) {
+		if (inode->i_nlink) {
+			drop_nlink(inode);
+		} else {
+			p9_debug(P9_DEBUG_VFS,
+						"WARNING: unexpected i_nlink zero %d inode %ld\n",
+						inode->i_nlink, inode->i_ino);
+		}
+	}
 }
 
 /**
@@ -489,6 +507,9 @@ static int v9fs_remove(struct inode *dir, struct dentry *dentry, int flags)
 		} else
 			v9fs_dec_count(inode);
 
+		if (inode->i_nlink <= 0)	/* no more refs unhash it */
+			remove_inode_hash(inode);
+
 		v9fs_invalidate_inode_attr(inode);
 		v9fs_invalidate_inode_attr(dir);
 
@@ -554,7 +575,7 @@ v9fs_create(struct v9fs_session_info *v9ses, struct inode *dir,
 		/*
 		 * instantiate inode and assign the unopened fid to the dentry
 		 */
-		inode = v9fs_get_inode_from_fid(v9ses, fid, dir->i_sb);
+		inode = v9fs_get_inode_from_fid(v9ses, fid, dir->i_sb, true);
 		if (IS_ERR(inode)) {
 			err = PTR_ERR(inode);
 			p9_debug(P9_DEBUG_VFS,
@@ -683,7 +704,7 @@ struct dentry *v9fs_vfs_lookup(struct inode *dir, struct dentry *dentry,
 	else if (IS_ERR(fid))
 		inode = ERR_CAST(fid);
 	else
-		inode = v9fs_get_inode_from_fid(v9ses, fid, dir->i_sb);
+		inode = v9fs_get_inode_from_fid(v9ses, fid, dir->i_sb, false);
 	/*
 	 * If we had a rename on the server and a parallel lookup
 	 * for the new name, then make sure we instantiate with
diff --git a/fs/9p/vfs_inode_dotl.c b/fs/9p/vfs_inode_dotl.c
index 55dde186041a..c61b97bd13b9 100644
--- a/fs/9p/vfs_inode_dotl.c
+++ b/fs/9p/vfs_inode_dotl.c
@@ -52,7 +52,10 @@ static kgid_t v9fs_get_fsgid_for_create(struct inode *dir_inode)
 	return current_fsgid();
 }
 
-struct inode *v9fs_fid_iget_dotl(struct super_block *sb, struct p9_fid *fid)
+
+
+struct inode *
+v9fs_fid_iget_dotl(struct super_block *sb, struct p9_fid *fid, bool new)
 {
 	int retval;
 	struct inode *inode;
@@ -62,8 +65,18 @@ struct inode *v9fs_fid_iget_dotl(struct super_block *sb, struct p9_fid *fid)
 	inode = iget_locked(sb, QID2INO(&fid->qid));
 	if (unlikely(!inode))
 		return ERR_PTR(-ENOMEM);
-	if (!(inode->i_state & I_NEW))
-		return inode;
+	if (!(inode->i_state & I_NEW)) {
+		if (!new) {
+			goto done;
+		} else { /* deal with race condition in inode number reuse */
+			p9_debug(P9_DEBUG_ERROR, "WARNING: Inode collision %lx\n",
+						inode->i_ino);
+			iput(inode);
+			remove_inode_hash(inode);
+			inode = iget_locked(sb, QID2INO(&fid->qid));
+			WARN_ON(!(inode->i_state & I_NEW));
+		}
+	}
 
 	/*
 	 * initialize the inode with the stat info
@@ -90,12 +103,11 @@ struct inode *v9fs_fid_iget_dotl(struct super_block *sb, struct p9_fid *fid)
 		goto error;
 
 	unlock_new_inode(inode);
-
+done:
 	return inode;
 error:
 	iget_failed(inode);
 	return ERR_PTR(retval);
-
 }
 
 struct dotl_openflag_map {
@@ -247,7 +259,7 @@ v9fs_vfs_atomic_open_dotl(struct inode *dir, struct dentry *dentry,
 		p9_debug(P9_DEBUG_VFS, "p9_client_walk failed %d\n", err);
 		goto out;
 	}
-	inode = v9fs_fid_iget_dotl(dir->i_sb, fid);
+	inode = v9fs_fid_iget_dotl(dir->i_sb, fid, true);
 	if (IS_ERR(inode)) {
 		err = PTR_ERR(inode);
 		p9_debug(P9_DEBUG_VFS, "inode creation failed %d\n", err);
@@ -340,7 +352,7 @@ static int v9fs_vfs_mkdir_dotl(struct mnt_idmap *idmap,
 	}
 
 	/* instantiate inode and assign the unopened fid to the dentry */
-	inode = v9fs_fid_iget_dotl(dir->i_sb, fid);
+	inode = v9fs_fid_iget_dotl(dir->i_sb, fid, true);
 	if (IS_ERR(inode)) {
 		err = PTR_ERR(inode);
 		p9_debug(P9_DEBUG_VFS, "inode creation failed %d\n",
@@ -776,7 +788,7 @@ v9fs_vfs_mknod_dotl(struct mnt_idmap *idmap, struct inode *dir,
 			 err);
 		goto error;
 	}
-	inode = v9fs_fid_iget_dotl(dir->i_sb, fid);
+	inode = v9fs_fid_iget_dotl(dir->i_sb, fid, true);
 	if (IS_ERR(inode)) {
 		err = PTR_ERR(inode);
 		p9_debug(P9_DEBUG_VFS, "inode creation failed %d\n",
diff --git a/fs/9p/vfs_super.c b/fs/9p/vfs_super.c
index 55e67e36ae68..f52fdf42945c 100644
--- a/fs/9p/vfs_super.c
+++ b/fs/9p/vfs_super.c
@@ -139,7 +139,7 @@ static struct dentry *v9fs_mount(struct file_system_type *fs_type, int flags,
 	else
 		sb->s_d_op = &v9fs_dentry_operations;
 
-	inode = v9fs_get_inode_from_fid(v9ses, fid, sb);
+	inode = v9fs_get_inode_from_fid(v9ses, fid, sb, true);
 	if (IS_ERR(inode)) {
 		retval = PTR_ERR(inode);
 		goto release_sb;