On 11/07, Mina Almasry wrote: > On Thu, Nov 7, 2024 at 5:30 PM Stanislav Fomichev <stfomichev@xxxxxxxxx> wrote: > > > > On 11/07, Mina Almasry wrote: > > > Document new behavior when the number of frags passed is too big. > > > > > > Signed-off-by: Mina Almasry <almasrymina@xxxxxxxxxx> > > > --- > > > Documentation/networking/devmem.rst | 9 +++++++++ > > > 1 file changed, 9 insertions(+) > > > > > > diff --git a/Documentation/networking/devmem.rst b/Documentation/networking/devmem.rst > > > index a55bf21f671c..d95363645331 100644 > > > --- a/Documentation/networking/devmem.rst > > > +++ b/Documentation/networking/devmem.rst > > > @@ -225,6 +225,15 @@ The user must ensure the tokens are returned to the kernel in a timely manner. > > > Failure to do so will exhaust the limited dmabuf that is bound to the RX queue > > > and will lead to packet drops. > > > > > > +The user must pass no more than 128 tokens, with no more than 1024 total frags > > > +among the token->token_count across all the tokens. If the user provides more > > > +than 1024 frags, the kernel will free up to 1024 frags and return early. > > > + > > > +The kernel returns the number of actual frags freed. The number of frags freed > > > +can be less than the tokens provided by the user in case of: > > > + > > > > [..] > > > > > +(a) an internal kernel leak bug. > > > > If you're gonna respin, might be worth mentioning that the dmesg > > will contain a warning in case of a leak? > > We will not actually warn in the likely cases of leak. > > We warn when we find an entry in the xarray that is not a net_iov, or > if napi_pp_put_page fails on that net_iov. Both are very unlikely to > happen honestly. > > The likely 'leaks' are when we don't find the frag_id in the xarray. > We do not warn on that because the user can intentionally trigger the > warning with invalid input. If the user is actually giving valid input > and the warn still happens, likely a kernel bug like I mentioned in > another thread, but we still don't warn. In this case, maybe don't mention the leaks at all? If it's not actionable, not sure how it helps?
