On Tue, Aug 08, 2017 at 05:23:50PM +0900, Sergey Senozhatsky wrote: > Hello Minchan, > > On (08/08/17 17:13), Minchan Kim wrote: > > Hi Sergey, > > > > On Tue, Aug 08, 2017 at 04:02:26PM +0900, Sergey Senozhatsky wrote: > > > On (08/08/17 15:50), Minchan Kim wrote: > > > > With on-stack-bio, rw_page interface doesn't provide a clear performance > > > > benefit for zram and surely has a maintenance burden, so remove the > > > > last user to remove rw_page completely. > > > > > > OK, never really liked it, I think we had that conversation before. > > > > > > as far as I remember, zram_rw_page() was the reason we had to do some > > > tricks with init_lock to make lockdep happy. may be now we can "simplify" > > > the things back. > > > > I cannot remember. Blame my brain. ;-) > > no worries. I didn't remember it clearly as well, hence the "may be" part. > > commit 08eee69fcf6baea543a2b4d2a2fcba0e61aa3160 > Author: Minchan Kim > > zram: remove init_lock in zram_make_request > > Admin could reset zram during I/O operation going on so we have used > zram->init_lock as read-side lock in I/O path to prevent sudden zram > meta freeing. > > However, the init_lock is really troublesome. We can't do call > zram_meta_alloc under init_lock due to lockdep splat because > zram_rw_page is one of the function under reclaim path and hold it as > read_lock while other places in process context hold it as write_lock. > So, we have used allocation out of the lock to avoid lockdep warn but > it's not good for readability and fainally, I met another lockdep splat > between init_lock and cpu_hotplug from kmem_cache_destroy during working > zsmalloc compaction. :( I don't think this patch is going to change anything with respect to the use of init_lock. You're still going to be called in the reclaim path, no longer through rw_page, but through the bio path instead. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
