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From: David Howells <dhowells@redhat.com>
To: slava@dubeyko.com
Cc: dhowells@redhat.com, Alex Markuze <amarkuze@redhat.com>,
	Xiubo Li <xiubli@redhat.com>, Ilya Dryomov <idryomov@gmail.com>,
	Jeff Layton <jlayton@kernel.org>,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	Christian Brauner <brauner@kernel.org>,
	ceph-devel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	linux-kernel@vger.kernel.org, Slava.Dubeyko@ibm.com
Subject: Re: Does ceph_fill_inode() mishandle I_NEW?
Date: Thu, 13 Mar 2025 20:47:47 +0000	[thread overview]
Message-ID: <1468676.1741898867@warthog.procyon.org.uk> (raw)
In-Reply-To: <3cc1ac78a01be069f79dcf82e2f3e9bfe28d9a4b.camel@dubeyko.com>

slava@dubeyko.com wrote:

> What do you mean by mishandling? Do you imply that Ceph has to set up
> the I_NEW somehow? Is it not VFS responsibility?

No - I mean that if I_NEW *isn't* set when the function is called,
ceph_fill_inode() will go and partially reinitialise the inode.  Now, having
reviewed the code in more depth and talked to Jeff Layton about it, I think
that the non-I_NEW pass will only change pointers with some sort of locking
and will release the old target - though it may overwrite some pointers with
the same value without protection (i_fops for example).

That said, if it's possible for *two* processes to be going through that
function without I_NEW set, you can get places where both of them will try
freeing the old data and replacing it with new without any locking - but I
don't know if that can happen.

David


  reply	other threads:[~2025-03-13 20:47 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2025-03-13 10:17 Does ceph_fill_inode() mishandle I_NEW? David Howells
2025-03-13 19:14 ` slava
2025-03-13 20:47   ` David Howells [this message]
2025-03-13 21:46     ` Viacheslav Dubeyko
2025-03-13 23:47       ` David Howells
2025-03-13 22:47     ` Jeff Layton
2025-03-13 23:37       ` David Howells

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