Hi,

On 8/14/2024 2:34 PM, Jingbo Xu wrote:

Hi, Tao,

On 4/26/24 10:39 PM, Hou Tao wrote:

quoted

From: Hou Tao <redacted>

Hi,

The patch set aims to fix the warning related to an abnormal size
parameter of kmalloc() in virtiofs. Patch #1 fixes it by introducing
use_pages_for_kvec_io option in fuse_conn and enabling it in virtiofs.
Beside the abnormal size parameter for kmalloc, the gfp parameter is
also questionable: GFP_ATOMIC is used even when the allocation occurs
in a kworker context. Patch #2 fixes it by using GFP_NOFS when the
allocation is initiated by the kworker. For more details, please check
the individual patches.

As usual, comments are always welcome.

Change Log:

v3:
 * introduce use_pages_for_kvec_io for virtiofs. When the option is
   enabled, fuse will use iov_iter_extract_pages() to construct a page
   array and pass the pages array instead of a pointer to virtiofs.
   The benefit is twofold: the length of the data passed to virtiofs is
   limited by max_pages, and there is no memory copy compared with v2.

v2: https://lore.kernel.org/linux-fsdevel/20240228144126.2864064-1-houtao@huaweicloud.com/ (local)
  * 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/ (local)

[1]: https://lore.kernel.org/linux-fsdevel/20240105105305.4052672-1-houtao@huaweicloud.com/ (local)

Hou Tao (2):
  virtiofs: use pages instead of pointer for kernel direct IO
  virtiofs: use GFP_NOFS when enqueuing request through kworker

 fs/fuse/file.c      | 12 ++++++++----
 fs/fuse/fuse_i.h    |  3 +++
 fs/fuse/virtio_fs.c | 25 ++++++++++++++++---------
 3 files changed, 27 insertions(+), 13 deletions(-)

We also encountered the same issue as [1] these days when attempting to
insmod a module with ~6MB size, which is upon a virtiofs filesystem.

It would be much helpful if this issue has a standard fix in the
upstream.  I see there will be v4 when reading through the mailing
thread.  Glad to know if there's any update to this series.

Being busy with other stuff these days. I hope to send v4 before next
weekend.

[1]
https://lore.kernel.org/linux-fsdevel/20240103105929.1902658-1-houtao@huaweicloud.com/ (local)