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From:   David Howells <dhowells@redhat.com>
In-Reply-To: <Y/y5rFX2koj2W6Wa@casper.infradead.org>
References: <Y/y5rFX2koj2W6Wa@casper.infradead.org> <20230202204428.3267832-5-willy@infradead.org> <20230202204428.3267832-1-willy@infradead.org> <2730679.1677505767@warthog.procyon.org.uk>
To:     Matthew Wilcox <willy@infradead.org>
Cc:     dhowells@redhat.com, linux-fsdevel@vger.kernel.org,
        linux-afs@lists.infradead.org, linux-btrfs@vger.kernel.org,
        linux-ext4@vger.kernel.org, linux-mm@kvack.org,
        Hugh Dickins <hughd@google.com>, linux-kernel@vger.kernel.org,
        fstests@vger.kernel.org
Subject: Re: [PATCH 4/5] afs: Zero bytes after 'oldsize' if we're expanding the file
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Date:   Mon, 27 Feb 2023 14:49:59 +0000
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Matthew Wilcox <willy@infradead.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