On Sat, Jan 7, 2017 at 2:15 AM, <sf...@users.sourceforge.net> wrote: > Hello Arun, > > Arun Chandran: >> 4) Now if I cd to /mnt/mnt and do 'ls' it hangs and I get the below oops. >> >> >> # dmesg >> [ 148.855382] ------------[ cut here ]------------ >> [ 148.855382] kernel BUG at fs/aufs/sbinfo.c:336! > ::: > > That is interesting. > Smack enters aufs twice. > > Generally a systemcall enters VFS and then aufs. Once it enters aufs, > aufs calls si_read_lock() which prohibits the branch manipulation > (add/del branches in aufs) during the systemcall. Leaving aufs, > si_read_unlock() is called and the branch manipulataion is > allowed. Finally VFS and the systemcall return to the userspace. > > According to your stack trace, > - lstat(2) is issued > - VFS tries resolving the given path, and calls aufs_lookup(). > - aufs finds the file (probably), and calls d_instatiate() which caches > the filepath in memory. > - d_instantiate() calls smack_d_instantiate(). obviously it should > happen when smack is enabled only. > - smack_d_instantiate() wants a specific XATTR set to that file and > calls aufs_getxattr(). > What a surprise! aufs_getxattr() should be called via systemcall as > getxattr(2). The process should not re-enter aufs before completing > aufs_lookup(). At least, aufs doesn't expect such behaviour. And aufs > detects this "re-entering" behaviour and produces this message. If you > had not enabled CONFIG_AUFS_DEBUG, the message would not be > produced. But the behaviour would not be reliable anymore, I am > afraid. It was good to enable CONFIG_AUFS_DEBUG. > > I don't know why smack people designed such behaviour. That is > inetresting. At the same time, I think it ugly. Why didn't they create a > hook at the very end of lookup, I wonder. > > Anyway here is a quick hack for you. Won't you test it? > > > J. R. Okajima >
Thank you for the quick reply. I have tested the patch. 'ls' behavior is the same, it hangs. There are no error messages coming now may be it is doing something inside au_h_path_getattr() with holding the lock (When printed locked is -1). --Arun ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, SlashDot.org! http://sdm.link/slashdot
