I am having the same problem on ubuntu 16.04.2, kernel 4.4.0-75-generic, and on a mint 18 system, kernel 4.4.0-21-generic. I have several cifs mounts, and if any one server becomes unresponsive, then any process attempting to access the mounts will hang indefinitely. If I unmount using -l and wait several minutes, eventually these hung processes will resume (with an error). I am mounting with the "soft" option.
The hung process stack looks like: $ sudo cat /proc/7771/stack [<ffffffffc030970d>] cifs_reconnect_tcon+0x9d/0x340 [cifs] [<ffffffffc0309a5a>] smb_init+0x2a/0x50 [cifs] [<ffffffffc0310c53>] CIFSSMBQPathInfo+0x63/0x2e0 [cifs] [<ffffffffc033c20f>] cifs_query_path_info+0x6f/0x1a0 [cifs] [<ffffffffc032ae80>] cifs_get_inode_info+0x390/0x8f0 [cifs] [<ffffffffc032d425>] cifs_revalidate_dentry_attr+0x1d5/0x250 [cifs] [<ffffffffc032d551>] cifs_getattr+0x51/0x110 [cifs] [<ffffffff81213a6c>] vfs_getattr_nosec+0x2c/0x40 [<ffffffff81213c86>] vfs_getattr+0x26/0x30 [<ffffffff81213d68>] vfs_fstatat+0x78/0xc0 [<ffffffff81214311>] SYSC_newlstat+0x31/0x60 [<ffffffff8121444e>] SyS_newlstat+0xe/0x10 [<ffffffff8183b972>] entry_SYSCALL_64_fastpath+0x16/0x71 [<ffffffffffffffff>] 0xffffffffffffffff ** Changed in: linux (Ubuntu) Status: Expired => New -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1073648 Title: CIFS hangs if server goes down, even if 'soft' is enabled To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1073648/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs