Re: [PATCH] hfsplus: don't use BUG_ON() in hfsplus_create_attributes_file()

[Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>]

On 2025/07/10 3:33, Viacheslav Dubeyko wrote:
> My worry that we could have a race condition here. Let's imagine that two
> threads are trying to call __hfsplus_setxattr() and both will try to create the
> Attributes File. Potentially, we could end in situation when inode could have
> not zero size during hfsplus_create_attributes_file() in one thread because
> another thread in the middle of Attributes File creation. Could we double check
> that we don't have the race condition here? Otherwise, we need to make much
> cleaner fix of this issue.

I think that there is some sort of race window, for
https://elixir.bootlin.com/linux/v6.15.5/source/fs/hfsplus/xattr.c#L145
explains that if more than one thread concurrently reached

	if (!HFSPLUS_SB(inode->i_sb)->attr_tree) {
		err = hfsplus_create_attributes_file(inode->i_sb);
		if (unlikely(err))
			goto end_setxattr;
	}

path, all threads except one thread will fail with -EAGAIN.