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    Subject[PATCH 0/3] Fix IO error reporting on fsync()
      Hello,

    current code in buffer.c has two pitfalls that cause problems with IO
    error reporting of filesystems using mapping->private_list for their
    metadata buffers (e.g. ext2).
    The first problem is that end_io_async_write() does not mark IO error
    in the buffer flags, only in the page flags. Hence fsync_buffers_list()
    does not find out that some IO error has occured and will not report it.
    The second problem is that buffers from private_list can be freed
    (e.g. under memory pressure) and if fsync_buffer_list() is called after
    that moment, IO error is lost - note that metadata buffers mark AS_EIO
    on the *device mapping* not on the inode mapping.
    Following series of three patches tries to fix these problems. The
    approach I took (after some discussions with Andrew) is introducing
    dummy buffer_head in the mapping instead of private_list. This dummy
    buffer head serves as a head of metadata buffer list and also collects
    IO errors from other buffers on the list (see the third patch for more
    details). This is kind of compromise between introducing a pointer to
    inode's address_space into each buffer and between using list_head
    instead of buffer_head and playing some dirty tricks to recognize that
    one particular list_head is actually from address_space and not from
    buffer_head. Any suggestions for improvements welcome.

    Honza
    --
    Jan Kara <jack@suse.cz>
    SuSE CR Labs
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