On Mon, May 9, 2016 at 12:32 AM, Al Viro <viro@xxxxxxxxxxxxxxxxxx> wrote: > On Sun, May 08, 2016 at 03:16:29PM +0100, Al Viro wrote: > >> Very strange. We grab that rwsem at the entry into nfs_call_unlink() >> and then either release it there and return or call nfs_do_call_unlink(). >> Which arranges for eventual call of nfs_async_unlink_release() (via >> ->rpc_release); nfs_async_unlink_release() releases the rwsem. Nobody else >> releases it (on the read side, that is). >> >> The only kinda-sorta possibility I see here is that the inode we are >> unlocking in that nfs_async_unlink_release() is not the one we'd locked >> in nfs_call_unlink() that has lead to it. That really shouldn't happen, >> though... Just to verify whether that's what we are hitting, could you >> try to reproduce that thing with the patch below on top of -next and see >> if it triggers any of those WARN_ON? > > D'oh... Lockdep warnings are easy to trigger (and, AFAICS, bogus). > up_read/down_read in fs/nfs/unlink.c should be replaced with > up_read_non_owner/down_read_non_owner, lest the lockdep gets confused. > Hangs are different - I've no idea what's triggering those. I've seen > something similar on that -next, but not on work.lookups. > > The joy of bisecting -next... <a couple of hours later> > 9317bb69824ec8d078b0b786b6971aedb0af3d4f is the first bad commit > commit 9317bb69824ec8d078b0b786b6971aedb0af3d4f > Author: Eric Dumazet <edumazet@xxxxxxxxxx> > Date: Mon Apr 25 10:39:32 2016 -0700 > > net: SOCKWQ_ASYNC_NOSPACE optimizations > > Reverting changes to sk_set_bit/sk_clear_bit gets rid of the hangs. Plain > revert gives a conflict, since there had been additional change in > "net: SOCKWQ_ASYNC_WAITDATA optimizations"; removing both fixed the hangs. > > Note that hangs appear without any fs/nfs/unlink.c modifications being > there. When the hang happens it affects NFS traffic; ssh session still > works fine until it steps on a filesystem operation on NFS (i.e. you > can use builtins, access procfs, etc.) Yeah, the issue was reported last week ( http://www.spinics.net/lists/netdev/msg375777.html ), and I could not convince myself to add a new sock flag, like SOCK_FASYNC_STICKY. (Just in case NFS would ever call sock_fasync() with an empty fasync_list, and SOCK_FASYNC would be cleared again. -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
