• Jan Kara's avatar
    quota: Fix deadlock during path resolution · f00c9e44
    Jan Kara authored
    As Al Viro pointed out path resolution during Q_QUOTAON calls to quotactl
    is prone to deadlocks. We hold s_umount semaphore for reading during the
    path resolution and resolution itself may need to acquire the semaphore
    for writing when e. g. autofs mountpoint is passed.
    
    Solve the problem by performing the resolution before we get hold of the
    superblock (and thus s_umount semaphore). The whole thing is complicated
    by the fact that some filesystems (OCFS2) ignore the path argument. So to
    distinguish between filesystem which want the path and which do not we
    introduce new .quota_on_meta callback which does not get the path. OCFS2
    then uses this callback instead of old .quota_on.
    
    CC: Al Viro <viro@ZenIV.linux.org.uk>
    CC: Christoph Hellwig <hch@lst.de>
    CC: Ted Ts'o <tytso@mit.edu>
    CC: Joel Becker <joel.becker@oracle.com>
    Signed-off-by: default avatarJan Kara <jack@suse.cz>
    f00c9e44
super.c 62.3 KB