On 7/13/20 7:14 PM, Miklos Szeredi wrote: > 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. Agree, I was wrong here. >> 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. Got it, agree, it should not be a problem. > I'll write these up in the patch header. Thank you, Vasily Averin
