On 6/3/21 12:06 PM, Andres Freund wrote:

Hi,

On 2021-05-29 12:03:12 +0100, Pavel Begunkov wrote:

quoted

On 5/29/21 1:33 AM, Andres Freund wrote:

quoted

Hi,

I started to see buffer registration randomly failing with ENOMEM on
5.13. Registering buffer or two often succeeds, but more than that
rarely. Running the same program as root succeeds - but the user has a high
rlimit.

The issue is that io_sqe_buffer_register() doesn't initialize
imu. io_buffer_account_pin() does imu->acct_pages++, before calling
io_account_mem(ctx, imu->acct_pages);

Which means that a random amount of memory is being accounted for. On the first
few allocations this sometimes fails to fail because the memory is zero, but
after a bit of reuse...

Makes sense, thanks for digging in. I've just sent a patch, would
be great if you can test it or send your own.

Sorry for the slow response, I'm off this week. I did just get around to
test and unsurprisingly: The patch does fix the issue.

OK good, thanks for confirming, I did ship it out earlier today so
should be in the next -rc.

-- 
Jens Axboe