On 09/09/2013 08:40 PM, George Spelvin wrote:
I'm really wondering about only trying once before taking the write lock. Yes, using the lsbit is a cute hack, but are we using it for its cuteness rather than its effectiveness? Renames happen occasionally. If that causes all the current pathname translations to fall back to the write lock, that is fairly heavy. Worse, all of those translations will (unnecessarily) bump the write seqcount, triggering *other* translations to fail back to the write-lock path. One patch to fix this would be to have the fallback read algorithm take sl->lock but *not* touch sl->seqcount, so it wouldn't break concurrent readers.
Actually, a follow-up patch that I am planning to do is to introduce a read_seqlock() primitive in seqlock.h that does exactly that. Then the write_seqlock() in this patch will be modified to read_seqlock().
-Longman -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
