On Wed, May 15, 2024 at 08:15:20PM +0200, Mikulas Patocka wrote: > Hi > > I found this piece of code in alloc_multiple_bios: > int try = (gfp_flag & GFP_NOWAIT) ? 0 : 1;
I guess the above check is supposed to be (gfp_flag == GFP_NOWAIT)? > > The problem is that GFP_NOWAIT includes __GFP_KSWAPD_RECLAIM and GFP_IO > also includes __GFP_KSWAPD_RECLAIM - so the test always returns true and > we always start with try = 0. This code was introduced by the commit > 4a2fe2960891f1ccd7805d0973284fd44c2f12b4. > > I am inclined to remove this logic at all and always start with try = 0; > - trying to allocate bios first with GFP_NOWAIT makes no harm (and it > improves performance because we don't need to grab the lock) and if the > allocation fails, it is retried with GFP_NOIO. I think it is fine to simplify the logic in this way, and now GFP_NOWAIT is only for sending empty flush, which could be from fast path, and abnormal IO is supposed to be in slow path. Thanks, Ming
