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smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=eDtVrelY; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7B80E606A6C4 for ; Thu, 5 Nov 2026 19:32:41 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=eDtVrelY Received: by smtp.kernel.org (Postfix) with ESMTPSA id E5C1A1F00893; Thu, 5 Nov 2026 19:32:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793907161; bh=Rb2ofXzgJBc5fIuQP0w05xjk/81sHfOWEL8zO3J0XUA=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=eDtVrelYYt9il2577q40L8EJ4XtDnLbe9oqPCZ5DVXPhy2CZ8RykrXLqcT8lNJ9fo iVvdOiFyVuQs7f9uc0KWN9MENqV2XhI4rRvK3+VjAyx04aExFaeskqW93dB8KnV1I7 jXPC/Dq+sLpMiFkrvl1FXVJfY5SmBtdGcpXVpAosWwzVpgGOAtgpDNtkSivs3sMb0S idxJlASIgnR6P/pT9DmadA3pyNe/7F5fBJgEg6bIU8TZ5JFBDrGQZ6Q/e/u9IVIB7y yZXuho1Kj6QIDbZlEjN5wDAh5ZVw8ddXkVoI6kVGhOjvfJ+tc5dncmBzIgU7aioe/k V1zZhbj+ZI/kg== Message-ID: <7dc47941-0c84-4260-bf9c-1a9bbe4d4f08@kernel.org> Date: Thu, 5 Nov 2026 20:32:37 +0100 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] shmem: skip empty unmap ranges when punching holes To: Hungyu Lin , hughd@google.com Cc: baolin.wang@linux.alibaba.com, akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20261105055619.58289-1-dennylin0707@gmail.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 11/5/26 06:56, Hungyu Lin wrote: > When a hole ends before the first page boundary, shmem_fallocate() > calculates unmap_end as -1. Casting it to u64 makes the range check > succeed even though the hole contains no complete pages. > > For example, punching one byte at offset zero calls unmap_mapping_range() > with a zero length, which means unmap to the end of the file. The file > contents are preserved outside the hole, but unrelated mappings are > removed and must fault back in. This can be reproduced with fallocate -p > -o 0 -l 1 on a mapped tmpfs file. > > Keep unmap_end as the exclusive rounded end instead of subtracting one, > and adjust shmem_falloc.next and the unmap length accordingly. A hole > ending before the first page boundary then has an end of zero, so the > unsigned range check skips the empty range. Retain the unsigned > comparison so rounding the start near the maximum file offset continues > to be handled correctly. > > Fixes: 83e4fa9c16e4 ("tmpfs: support fallocate FALLOC_FL_PUNCH_HOLE") > Reviewed-by: Baolin Wang > Signed-off-by: Hungyu Lin > --- > Changes in v2: Thanks, I'll wait a couple of days and then queue this for the next merge window. -- Cheers, David