Hi, Chris Mason > -----Original Message----- > From: Chris Mason [mailto:clm@xxxxxx] > Sent: Thursday, January 21, 2016 1:48 AM > To: Zhao Lei <zhaolei@xxxxxxxxxxxxxx>; linux-btrfs@xxxxxxxxxxxxxxx > Subject: Re: [PATCH 1/2] btrfs: reada: limit max works count > > On Wed, Jan 20, 2016 at 10:16:27AM -0500, Chris Mason wrote: > > On Tue, Jan 12, 2016 at 03:46:26PM +0800, Zhao Lei wrote: > > > reada create 2 works for each level of tree in recursion. > > > > > > In case of a tree having many levels, the number of created works is > > > 2^level_of_tree. > > > Actually we don't need so many works in parallel, this patch limit > > > max works to BTRFS_MAX_MIRRORS * 2. > > > > Hi, > > > > I don't think you end up calling atomic_dec() for every time that > > reada_start_machine() is called. Also, I'd rather not have a global > > static variable to limit the parallel workers, when we have more than > > one FS mounted it'll end up limiting things too much. > > > > With this patch applied, I'm seeing deadlocks during btrfs/066. You > > have to run the scrub tests as well, basically we're just getting > > fsstress run alongside scrub. > > > > I'll run a few more times with it reverted to make sure, but I think > > it's the root cause. > > I spoke too soon, it ended up deadlocking a few tests later. > In logic, even if the calculation of atomic_dec() in this patch having bug, in worst condition, reada will works in single-thread mode, and will not introduce deadlock. And by looking the backtrace in this mail, maybe it is caused by reada_control->elems in someplace of this patchset. I recheck xfstests/066 in both vm and physical machine, on top of my pull-request git today, with btrfs-progs 4.4 for many times, but had not triggered the bug. Could you tell me your test environment(TEST_DEV size, mount option), and odds of fails in btrfs/066? Thanks Zhaolei > Sorry for now I'm pulling all the reada patches. We'll sort out bug fixes vs cleanups in later rcs. > > With all of the reada patches removed, the deadlocks are gone. > > -chris -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
