Re: Fwd: Re: A new look at old NFS readdir() problems?

On 01/02/2025 3:42 pm, Thomas Munro wrote:
> On Fri, Jan 3, 2025 at 10:16 AM Larry Rosenman <ler@lerctr.org> wrote:
>> What about doing what Rick suggests?
>> do {
>>        dir = opendir("X");
>>         dp = readdir(dir);
>>         if (dp != NULL)
>>              unlink(dp->d_name);
>>          close(dir);
>> } while (dp != NULL);
>> ?
> 
> That only works for unlink loops where we expect no concurrent
> modifications.  DROP DATABASE qualifies, but we use readdir() on
> directories that might be changing in various other places, including
> backups.  They'd silently fail to do their job, and can't use that
> technique as they aren't unlinking as they go and so they would never
> make progress.  Which leads to the lipstick/pig conclusion: we'd have
> other, worse, buggy behaviour still.
> 
> It might be possible to make our own readdir snapshot thing that
> checks a shmem counter of all links/unlinks before and after and
> retries.  But ugh...

Would it make sense for ONLY drop database to have the above loop?

-- 
Larry Rosenman                     http://www.lerctr.org/~ler
Phone: +1 214-642-9640                 E-Mail: ler@lerctr.org
US Mail: 13425 Ranch Road 620 N, Apt 718, Austin, TX 78717-1010