On Mon, Jul 13, 2020 at 10:02 AM Vasily Averin <vvs@xxxxxxxxxxxxx> wrote: > > On 7/11/20 7:01 AM, Miklos Szeredi wrote: > > On Thu, Jun 25, 2020 at 11:02 AM Vasily Averin <vvs@xxxxxxxxxxxxx> wrote: > >> > >> In current implementation fuse_writepages_fill() tries to share the code: > >> for new wpa it calls tree_insert() with num_pages = 0 > >> then switches to common code used non-modified num_pages > >> and increments it at the very end. > >> > >> Though it triggers WARN_ON(!wpa->ia.ap.num_pages) in tree_insert() > >> WARNING: CPU: 1 PID: 17211 at fs/fuse/file.c:1728 tree_insert+0xab/0xc0 [fuse] > >> RIP: 0010:tree_insert+0xab/0xc0 [fuse] > >> Call Trace: > >> fuse_writepages_fill+0x5da/0x6a0 [fuse] > >> write_cache_pages+0x171/0x470 > >> fuse_writepages+0x8a/0x100 [fuse] > >> do_writepages+0x43/0xe0 > >> > >> This patch re-works fuse_writepages_fill() to call tree_insert() > >> with num_pages = 1 and avoids its subsequent increment and > >> an extra spin_lock(&fi->lock) for newly added wpa. > > > > Looks good. However, I don't like the way fuse_writepage_in_flight() > > is silently changed to insert page into the rb_tree. Also the > > insertion can be merged with the search for in-flight and be done > > unconditionally to simplify the logic. See attached patch. > > Your patch looks correct for me except 2 things: Thanks for reviewing. > 1) you have lost "data->wpa = NULL;" when fuse_writepage_add() returns false. This is intentional, because this is in the !data->wpa branch. > 2) in the same case old code did not set data->orig_pages[ap->num_pages] = page; That is also intentional, in this case the origi_pages[0] is either overwritten with the next page or discarded due to data->wpa being NULL. I'll write these up in the patch header. Thanks, Miklos
