• Andrew Morton's avatar
    [PATCH] Fix inode size accounting race · 7619fd2b
    Andrew Morton authored
    Since Jan removed the lock_kernel()s in inode_add_bytes() and
    inode_sub_bytes(), these functions have been racy.
    
    One problematic workload has been discovered in which concurrent writepage
    and truncate on SMP quickly causes i_blocks to go negative.  writepage() does
    not take i_sem, and it seems that for ext2, there are no other locks in
    force when inode_add_bytes() is called.
    
    Putting the BKL back in there is not acceptable.  To fix this race I have
    added a new spinlock "i_lock" to the inode.
    
    That lock is presently used to protect i_bytes and i_blocks.  We could use it
    to protect i_size as well.
    
    The splitting of the used disk space into i_blocks and i_bytes is silly - we
    should nuke all that and just have a bare loff_t i_usedbytes.   Later.
    7619fd2b
ksyms.c 16.6 KB