On 08.07.22 19:37, Demi Marie Obenour wrote:
Hello Demi Marie
Please add subsystem to the commit subject, for example "xen/gntdev:".
> The error paths of gntdev_mmap() can call unmap_grant_pages() even
> though not all of the pages have been successfully mapped. This will
> trigger the WARN_ON()s in __unmap_grant_pages_done(). The number of
> warnings can be very large; I have observed thousands of lines of
> warnings in the systemd journal.
>
> Avoid this problem by only warning on unmapping failure if the handle
> being unmapped is not INVALID_GRANT_HANDLE. The handle field of any
> page that was not successfully mapped will be INVALID_GRANT_HANDLE, so
> this catches all cases where unmapping can legitimately fail.
>
> Suggested-by: Juergen Gross <jgross@xxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Demi Marie Obenour <demi@xxxxxxxxxxxxxxxxxxxxxx>
> Fixes: dbe97cff7dd9 ("xen/gntdev: Avoid blocking in unmap_grant_pages()")
> ---
> drivers/xen/gntdev.c | 8 ++++++--
> 1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c
> index 4b56c39f766d4da68570d08d963f6ef40c8d9c37..22fcd503f4a4487d0aed147c94f432683dad8c73 100644
> --- a/drivers/xen/gntdev.c
> +++ b/drivers/xen/gntdev.c
> @@ -396,13 +396,17 @@ static void __unmap_grant_pages_done(int result,
> unsigned int offset = data->unmap_ops - map->unmap_ops;
>
> for (i = 0; i < data->count; i++) {
> - WARN_ON(map->unmap_ops[offset+i].status);
> + WARN_ON(map->unmap_ops[offset+i].status &&
> + map->unmap_ops[offset+i].handle !=
> + INVALID_GRANT_HANDLE);
Nit: While extending the check I would clarify the first half of it:
"map->unmap_ops[offset+i].status != GNTST_okay"
> pr_debug("unmap handle=%d st=%d\n",
> map->unmap_ops[offset+i].handle,
> map->unmap_ops[offset+i].status);
> map->unmap_ops[offset+i].handle = INVALID_GRANT_HANDLE;
> if (use_ptemod) {
> - WARN_ON(map->kunmap_ops[offset+i].status);
> + WARN_ON(map->kunmap_ops[offset+i].status &&
> + map->kunmap_ops[offset+i].handle !=
> + INVALID_GRANT_HANDLE);
ditto
With updated subject:
Reviewed-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>
> pr_debug("kunmap handle=%u st=%d\n",
> map->kunmap_ops[offset+i].handle,
> map->kunmap_ops[offset+i].status);
--
Regards,
Oleksandr Tyshchenko
