Re: Regression in io_uring, leading to data corruption

[Timothy Pearson <tpearson@raptorengineering.com>]

----- Original Message -----
> From: "Jens Axboe" <axboe@kernel.dk>
> To: "Timothy Pearson" <tpearson@raptorengineering.com>
> Cc: "regressions" <regressions@lists.linux.dev>, "Pavel Begunkov" <asml.silence@gmail.com>
> Sent: Monday, November 13, 2023 2:47:13 PM
> Subject: Re: Regression in io_uring, leading to data corruption

> On 11/13/23 10:06 AM, Timothy Pearson wrote:
>> When the bug is hit, and if all other conditions are exactly correct,
>> *something* (still to be identified) writes 32 bytes of gibberish into
>> one of the mariadb in-RAM database pages at a random offset.
> 
> Do you have one or more examples of what those 32 bytes look like?
> Ideally more than one. Would be nice if we could deduce something from
> the content there. A long shot, but...

Assuming we're on byte boundaries, here are a few examples.  Problem is since the offset is random it's hard to know for certain how many zeroes start (or end) the block, so I've trimmed the zeroes off both ends of these three examples with the exception of a leading zero needed to get to a byte boundary:

45713881df1783472b45a32d373f59b6
3063d0146087fdfd7d03cc2ff3523588
0fbfcd0b37bc3b861c5bd51c4f0f1365

And I just realized I misspoke, it's 16 bytes (32 nibbles).  They don't really look like pointers, and they don't correlate with anything on disk.  I had already tried to figure out what this data is without much success, it's not even program code...