From: Hou Tao <houtao@huaweicloud.com>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: linux-fsdevel@vger.kernel.org, Miklos Szeredi <miklos@szeredi.hu>,
Vivek Goyal <vgoyal@redhat.com>,
Stefan Hajnoczi <stefanha@redhat.com>,
Bernd Schubert <bernd.schubert@fastmail.fm>,
Matthew Wilcox <willy@infradead.org>,
Benjamin Coddington <bcodding@redhat.com>,
linux-kernel@vger.kernel.org, virtualization@lists.linux.dev,
houtao1@huawei.com
Subject: Re: [PATCH v2 0/6] virtiofs: fix the warning for ITER_KVEC dio
Date: Tue, 23 Apr 2024 21:25:33 +0800 [thread overview]
Message-ID: <3a287e9b-55ad-dda9-5f53-c12536bad31d@huaweicloud.com> (raw)
In-Reply-To: <20240422160615-mutt-send-email-mst@kernel.org>
On 4/23/2024 4:06 AM, Michael S. Tsirkin wrote:
> On Tue, Apr 09, 2024 at 09:48:08AM +0800, Hou Tao wrote:
>> Hi,
>>
>> On 4/8/2024 3:45 PM, Michael S. Tsirkin wrote:
>>> On Wed, Feb 28, 2024 at 10:41:20PM +0800, Hou Tao wrote:
>>>> From: Hou Tao <houtao1@huawei.com>
>>>>
>>>> Hi,
>>>>
>>>> The patch set aims to fix the warning related to an abnormal size
>>>> parameter of kmalloc() in virtiofs. The warning occurred when attempting
>>>> to insert a 10MB sized kernel module kept in a virtiofs with cache
>>>> disabled. As analyzed in patch #1, the root cause is that the length of
>>>> the read buffer is no limited, and the read buffer is passed directly to
>>>> virtiofs through out_args[0].value. Therefore patch #1 limits the
>>>> length of the read buffer passed to virtiofs by using max_pages. However
>>>> it is not enough, because now the maximal value of max_pages is 256.
>>>> Consequently, when reading a 10MB-sized kernel module, the length of the
>>>> bounce buffer in virtiofs will be 40 + (256 * 4096), and kmalloc will
>>>> try to allocate 2MB from memory subsystem. The request for 2MB of
>>>> physically contiguous memory significantly stress the memory subsystem
>>>> and may fail indefinitely on hosts with fragmented memory. To address
>>>> this, patch #2~#5 use scattered pages in a bio_vec to replace the
>>>> kmalloc-allocated bounce buffer when the length of the bounce buffer for
>>>> KVEC_ITER dio is larger than PAGE_SIZE. The final issue with the
>>>> allocation of the bounce buffer and sg array in virtiofs is that
>>>> GFP_ATOMIC is used even when the allocation occurs in a kworker context.
>>>> Therefore the last patch uses GFP_NOFS for the allocation of both sg
>>>> array and bounce buffer when initiated by the kworker. For more details,
>>>> please check the individual patches.
>>>>
>>>> As usual, comments are always welcome.
>>>>
>>>> Change Log:
>>> Bernd should I just merge the patchset as is?
>>> It seems to fix a real problem and no one has the
>>> time to work on a better fix .... WDYT?
>> Sorry for the long delay. I am just start to prepare for v3. In v3, I
>> plan to avoid the unnecessary memory copy between fuse args and bio_vec.
>> Will post it before next week.
> Didn't happen before this week apparently.
Sorry for failing to make it this week. Being busy these two weeks. Hope
to send v3 out before the end of April.
>
>>>
>>>> v2:
>>>> * limit the length of ITER_KVEC dio by max_pages instead of the
>>>> newly-introduced max_nopage_rw. Using max_pages make the ITER_KVEC
>>>> dio being consistent with other rw operations.
>>>> * replace kmalloc-allocated bounce buffer by using a bounce buffer
>>>> backed by scattered pages when the length of the bounce buffer for
>>>> KVEC_ITER dio is larger than PAG_SIZE, so even on hosts with
>>>> fragmented memory, the KVEC_ITER dio can be handled normally by
>>>> virtiofs. (Bernd Schubert)
>>>> * merge the GFP_NOFS patch [1] into this patch-set and use
>>>> memalloc_nofs_{save|restore}+GFP_KERNEL instead of GFP_NOFS
>>>> (Benjamin Coddington)
>>>>
>>>> v1: https://lore.kernel.org/linux-fsdevel/20240103105929.1902658-1-houtao@huaweicloud.com/
>>>>
>>>> [1]: https://lore.kernel.org/linux-fsdevel/20240105105305.4052672-1-houtao@huaweicloud.com/
>>>>
>>>> Hou Tao (6):
>>>> fuse: limit the length of ITER_KVEC dio by max_pages
>>>> virtiofs: move alloc/free of argbuf into separated helpers
>>>> virtiofs: factor out more common methods for argbuf
>>>> virtiofs: support bounce buffer backed by scattered pages
>>>> virtiofs: use scattered bounce buffer for ITER_KVEC dio
>>>> virtiofs: use GFP_NOFS when enqueuing request through kworker
>>>>
>>>> fs/fuse/file.c | 12 +-
>>>> fs/fuse/virtio_fs.c | 336 +++++++++++++++++++++++++++++++++++++-------
>>>> 2 files changed, 296 insertions(+), 52 deletions(-)
>>>>
>>>> --
>>>> 2.29.2
prev parent reply other threads:[~2024-04-23 13:25 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-02-28 14:41 [PATCH v2 0/6] virtiofs: fix the warning for ITER_KVEC dio Hou Tao
2024-02-28 14:41 ` [PATCH v2 1/6] fuse: limit the length of ITER_KVEC dio by max_pages Hou Tao
2024-03-01 13:42 ` Miklos Szeredi
2024-03-09 4:26 ` Hou Tao
2024-03-13 23:02 ` Bernd Schubert
2024-02-28 14:41 ` [PATCH v2 2/6] virtiofs: move alloc/free of argbuf into separated helpers Hou Tao
2024-02-28 14:41 ` [PATCH v2 3/6] virtiofs: factor out more common methods for argbuf Hou Tao
2024-03-01 14:24 ` Miklos Szeredi
2024-03-09 4:27 ` Hou Tao
2024-02-28 14:41 ` [PATCH v2 4/6] virtiofs: support bounce buffer backed by scattered pages Hou Tao
2024-02-29 15:01 ` Brian Foster
2024-03-09 4:14 ` Hou Tao
2024-03-13 12:14 ` Brian Foster
2024-02-28 14:41 ` [PATCH v2 5/6] virtiofs: use scattered bounce buffer for ITER_KVEC dio Hou Tao
2024-02-28 14:41 ` [PATCH v2 6/6] virtiofs: use GFP_NOFS when enqueuing request through kworker Hou Tao
2024-04-08 7:45 ` [PATCH v2 0/6] virtiofs: fix the warning for ITER_KVEC dio Michael S. Tsirkin
2024-04-09 1:48 ` Hou Tao
2024-04-22 20:06 ` Michael S. Tsirkin
2024-04-22 21:11 ` Bernd Schubert
2024-04-23 13:25 ` Hou Tao [this message]
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