• Jeff Mahoney's avatar
    reiserfs: fix deadlock with nfs racing on create/lookup · a1457c0c
    Jeff Mahoney authored
    Reiserfs is currently able to be deadlocked by having two NFS clients
    where one has removed and recreated a file and another is accessing the
    file with an open file handle.
    If one client deletes and recreates a file with timing such that the
    recreated file obtains the same [dirid, objectid] pair as the original
    file while another client accesses the file via file handle, the create
    and lookup can race and deadlock if the lookup manages to create the
    in-memory inode first.
    The create thread, in insert_inode_locked4, will hold the write lock
    while waiting on the other inode to be unlocked. The lookup thread,
    anywhere in the iget path, will release and reacquire the write lock while
    it schedules. If it needs to reacquire the lock while the create thread
    has it, it will never be able to make forward progress because it needs
    to reacquire the lock before ultimately unlocking the inode.
    This patch drops the write lock across the insert_inode_locked4 call so
    that the ordering of inode_wait -> write lock is retained. Since this
    would have been the case before the BKL push-down, this is safe.
    Signed-off-by: default avatarJeff Mahoney <jeffm@suse.com>
    Signed-off-by: default avatarJan Kara <jack@suse.cz>
inode.c 92.6 KB