Excerpts from Greg Kroah-Hartman's message of August 9, 2021 12:27 pm:
> On Mon, Aug 09, 2021 at 09:23:00AM -0700, Linus Torvalds wrote:
>> On Mon, Aug 9, 2021 at 2:52 AM <gregkh@xxxxxxxxxxxxxxxxxxx> wrote:
>> >
>> > The patch below does not apply to the 4.4-stable tree.
>>
>> It shouldn't.
>>
>> The pipe buffer accounting and soft limits that introduced the whole
>> "limp along with limited pipe buffers" behavior that this fixes was
>> introduced by
>>
>> > Fixes: 759c01142a ("pipe: limit the per-user amount of pages allocated in pipes")
>>
>> ..which made it into 4.5.
>>
>> So 4.4 is unaffected and doesn't want this patch.
>
> But that commit showed up in 4.4.13 as fa6d0ba12a8e ("pipe: limit the
> per-user amount of pages allocated in pipes") which is why I asked about
> this. The code didn't look similar at all, so I couldn't easily figure
> out the backport myself :(
>
> Willy, any ideas?
>
> thanks,
>
> greg k-h
>
alloc_pipe_info was heavily modified in 09b4d19900 ("pipe: simplify
logic in alloc_pipe_info()") and a005ca0e68 ("pipe: fix limit checking
in alloc_pipe_info()"), which I think landed in 4.9 and weren't
backported. The backported patch should look similar to this:
@@ -621,7 +621,7 @@
if (!too_many_pipe_buffers_hard(user)) {
if (too_many_pipe_buffers_soft(user))
- pipe_bufs = 1;
+ pipe_bufs = 2;
pipe->bufs = kzalloc(sizeof(struct pipe_buffer) * pipe_bufs, GFP_KERNEL);
}
I can send a rebased patch, but I think we can also leave it the way it
is. It's a bit of an edge case; if nobody's hit it so far on 4.4, maybe
it can just stay this way until February. There's SLTS, but I don't
think they're interested in this kind of patch. Thoughts?
Cheers,
Alex.
