Re: [syzbot] Re: [syzbot] [fs?] possible deadlock in __simple_recursive_removal

[syzbot <syzbot+6d7771315ecb9233f395@syzkaller.appspotmail.com>]

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Subject: Re: [syzbot] [fs?] possible deadlock in __simple_recursive_removal
Author: lizhi.xu@windriver.com

#syz test

diff --git a/fs/binfmt_misc.c b/fs/binfmt_misc.c
index 760437a91648..537390c984ee 100644
--- a/fs/binfmt_misc.c
+++ b/fs/binfmt_misc.c
@@ -734,7 +734,7 @@ static ssize_t bm_entry_write(struct file *file, const char __user *buffer,
 	case 3:
 		/* Delete this handler. */
 		inode = d_inode(inode->i_sb->s_root);
-		inode_lock(inode);
+		inode_lock_nested(inode, I_MUTEX_PARENT);
 
 		/*
 		 * In order to add new element or remove elements from the list
diff --git a/fs/libfs.c b/fs/libfs.c
index 3bc6c3750b47..0e3e33c4f159 100644
--- a/fs/libfs.c
+++ b/fs/libfs.c
@@ -611,7 +611,7 @@ static void __simple_recursive_removal(struct dentry *dentry,
 		struct dentry *victim = NULL, *child;
 		struct inode *inode = this->d_inode;
 
-		inode_lock(inode);
+		inode_lock_nested(inode, I_MUTEX_CHILD);
 		if (d_is_dir(this))
 			inode->i_flags |= S_DEAD;
 		while ((child = find_next_child(this, victim)) == NULL) {
@@ -624,7 +624,7 @@ static void __simple_recursive_removal(struct dentry *dentry,
 			this = this->d_parent;
 			inode = this->d_inode;
 			if (!locked || victim != dentry)
-				inode_lock(inode);
+				inode_lock_nested(inode, I_MUTEX_CHILD);
 			if (simple_positive(victim)) {
 				d_invalidate(victim);	// avoid lost mounts
 				if (callback)