Re: [syzbot] [v9fs?] WARNING in v9fs_begin_writeback

[Edward Adam Davis <eadavis@qq.com>]

debug

#syz test: upstream c0ecd6388360

diff --git a/fs/9p/fid.c b/fs/9p/fid.c
index de009a33e0e2..a5b716b716d4 100644
--- a/fs/9p/fid.c
+++ b/fs/9p/fid.c
@@ -67,6 +67,7 @@ struct p9_fid *v9fs_fid_find_inode(struct inode *inode, bool want_writeable,
 
 	spin_lock(&inode->i_lock);
 	h = (struct hlist_head *)&inode->i_private;
+	printk("ino: %p, inode fid list is empty: %d, %s\n", inode, hlist_empty(h), __func__);
 	hlist_for_each_entry(fid, h, ilist) {
 		if (any || uid_eq(fid->uid, uid)) {
 			if (want_writeable && !v9fs_is_writeable(fid->mode)) {
diff --git a/fs/9p/vfs_file.c b/fs/9p/vfs_file.c
index 348cc90bf9c5..0da8ff7f38fb 100644
--- a/fs/9p/vfs_file.c
+++ b/fs/9p/vfs_file.c
@@ -44,6 +44,7 @@ int v9fs_file_open(struct inode *inode, struct file *file)
 	struct p9_fid *fid;
 	int omode;
 
+	printk("1ind: %p, %s\n", inode, __func__);
 	p9_debug(P9_DEBUG_VFS, "inode: %p file: %p\n", inode, file);
 	v9ses = v9fs_inode2v9ses(inode);
 	if (v9fs_proto_dotl(v9ses))
@@ -54,8 +55,10 @@ int v9fs_file_open(struct inode *inode, struct file *file)
 	fid = file->private_data;
 	if (!fid) {
 		fid = v9fs_fid_clone(file_dentry(file));
-		if (IS_ERR(fid))
-			return PTR_ERR(fid);
+		if (IS_ERR(fid)) {
+			err = PTR_ERR(fid);
+			goto error;
+		}
 
 		if ((v9ses->cache & CACHE_WRITEBACK) && (omode & P9_OWRITE)) {
 			int writeback_omode = (omode & ~P9_OWRITE) | P9_ORDWR;
@@ -72,7 +75,7 @@ int v9fs_file_open(struct inode *inode, struct file *file)
 		}
 		if (err < 0) {
 			p9_fid_put(fid);
-			return err;
+			goto error;
 		}
 		if ((file->f_flags & O_APPEND) &&
 			(!v9fs_proto_dotu(v9ses) && !v9fs_proto_dotl(v9ses)))
@@ -87,8 +90,12 @@ int v9fs_file_open(struct inode *inode, struct file *file)
 				   file->f_mode & FMODE_WRITE);
 #endif
 	v9fs_fid_add_modes(fid, v9ses->flags, v9ses->cache, file->f_flags);
+	printk("2ind: %p, %s\n", inode, __func__);
 	v9fs_open_fid_add(inode, &fid);
 	return 0;
+error:
+	printk("err: %d, ind: %p, %s\n", err, inode, __func__);
+
 }
 
 /**
diff --git a/fs/9p/vfs_inode.c b/fs/9p/vfs_inode.c
index fd72fc38c8f5..29a055f2fe7b 100644
--- a/fs/9p/vfs_inode.c
+++ b/fs/9p/vfs_inode.c
@@ -738,6 +738,7 @@ v9fs_vfs_atomic_open(struct inode *dir, struct dentry *dentry,
 	struct inode *inode;
 	int p9_omode;
 
+	printk("1ind: %p, %s\n", inode, __func__);
 	if (d_in_lookup(dentry)) {
 		res = v9fs_vfs_lookup(dir, dentry, 0);
 		if (IS_ERR(res))
@@ -781,6 +782,7 @@ v9fs_vfs_atomic_open(struct inode *dir, struct dentry *dentry,
 #endif
 
 	v9fs_fid_add_modes(fid, v9ses->flags, v9ses->cache, file->f_flags);
+	printk("2ind: %p, %s\n", inode, __func__);
 	v9fs_open_fid_add(inode, &fid);
 
 	file->f_mode |= FMODE_CREATED;
@@ -789,6 +791,7 @@ v9fs_vfs_atomic_open(struct inode *dir, struct dentry *dentry,
 	return err;
 
 error:
+	printk("err: %d, ind: %p, %s\n", err, inode, __func__);
 	p9_fid_put(fid);
 	goto out;
 }
diff --git a/fs/9p/vfs_inode_dotl.c b/fs/9p/vfs_inode_dotl.c
index c61b97bd13b9..3c4c744af0e8 100644
--- a/fs/9p/vfs_inode_dotl.c
+++ b/fs/9p/vfs_inode_dotl.c
@@ -194,6 +194,7 @@ v9fs_vfs_atomic_open_dotl(struct inode *dir, struct dentry *dentry,
 	struct posix_acl *pacl = NULL, *dacl = NULL;
 	struct dentry *res = NULL;
 
+	printk("1ind: %p, %s\n", inode, __func__);
 	if (d_in_lookup(dentry)) {
 		res = v9fs_vfs_lookup(dir, dentry, 0);
 		if (IS_ERR(res))
@@ -284,9 +285,11 @@ v9fs_vfs_atomic_open_dotl(struct inode *dir, struct dentry *dentry,
 	}
 #endif
 	v9fs_fid_add_modes(ofid, v9ses->flags, v9ses->cache, flags);
+	printk("2ind: %p, %s\n", inode, __func__);
 	v9fs_open_fid_add(inode, &ofid);
 	file->f_mode |= FMODE_CREATED;
 out:
+	printk("err: %d, ind: %p, %s\n", err, inode, __func__);
 	p9_fid_put(dfid);
 	p9_fid_put(ofid);
 	p9_fid_put(fid);