linux-kernel - Re: [PATCH 4/5] afs: Zero bytes after 'oldsize' if we're expanding the file

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Message-ID: <2736267.1677509399@warthog.procyon.org.uk>
Date:   Mon, 27 Feb 2023 14:49:59 +0000
From:   David Howells <dhowells@...hat.com>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     dhowells@...hat.com, linux-fsdevel@...r.kernel.org,
        linux-afs@...ts.infradead.org, linux-btrfs@...r.kernel.org,
        linux-ext4@...r.kernel.org, linux-mm@...ck.org,
        Hugh Dickins <hughd@...gle.com>, linux-kernel@...r.kernel.org,
        fstests@...r.kernel.org
Subject: Re: [PATCH 4/5] afs: Zero bytes after 'oldsize' if we're expanding the file

Matthew Wilcox <willy@...radead.org> wrote:

> I'll send a patch series with all of this; it doesn't seem terribly
> urgent.  Do you think there's a similar problem for AFS that Brian
> noted with the generic patch?

Probably not.  To avoid deadlocking itself, afs uses a mutex to prevent
writepages racing with truncate (vnode->validate_lock).

	commit ec0fa0b659144d9c68204d23f627b6a65fa53e50
	afs: Fix deadlock between writeback and truncate

the afs_setattr_edit_file() call that changes i_size and partially clears the
pagecache is applied to the local inode before the mutex is dropped.

David