• wengang wang's avatar
    ocfs2: fix rare stale inode errors when exporting via nfs · 6ca497a8
    wengang wang authored
    For nfs exporting, ocfs2_get_dentry() returns the dentry for fh.
    ocfs2_get_dentry() may read from disk when the inode is not in memory,
    without any cross cluster lock. this leads to the file system loading a
    stale inode.
    
    This patch fixes above problem.
    
    Solution is that in case of inode is not in memory, we get the cluster
    lock(PR) of alloc inode where the inode in question is allocated from (this
    causes node on which deletion is done sync the alloc inode) before reading
    out the inode itsself. then we check the bitmap in the group (the inode in
    question allcated from) to see if the bit is clear. if it's clear then it's
    stale. if the bit is set, we then check generation as the existing code
    does.
    
    We have to read out the inode in question from disk first to know its alloc
    slot and allot bit. And if its not stale we read it out using ocfs2_iget().
    The second read should then be from cache.
    
    And also we have to add a per superblock nfs_sync_lock to cover the lock for
    alloc inode and that for inode in question. this is because ocfs2_get_dentry()
    and ocfs2_delete_inode() lock on them in reverse order. nfs_sync_lock is locked
    in EX mode in ocfs2_get_dentry() and in PR mode in ocfs2_delete_inode(). so
    that mutliple ocfs2_delete_inode() can run concurrently in normal case.
    
    [mfasheh@suse.com: build warning fixes and comment cleanups]
    Signed-off-by: default avatarWengang Wang <wen.gang.wang@oracle.com>
    Acked-by: default avatarJoel Becker <joel.becker@oracle.com>
    Signed-off-by: default avatarMark Fasheh <mfasheh@suse.com>
    6ca497a8
dlmglue.c 105 KB