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    Subject[RFC][PATCH] ext3: don't read inode block if the buffer has a write error
    A transient I/O error can corrupt inode data.  Here is the scenario:

    (1) update inode_A at the block_B
    (2) pdflush writes out new inode_A to the filesystem, but it results
    in write I/O error, at this point, BH_Uptodate flag of the buffer
    for block_B is cleared and BH_Write_EIO is set
    (3) create new inode_C which located at block_B, and
    __ext3_get_inode_loc() tries to read on-disk block_B because the
    buffer is not uptodate
    (4) if it can read on-disk block_B successfully, inode_A is
    overwritten by old data

    This patch makes __ext3_get_inode_loc() not read the inode block if
    the buffer has BH_Write_EIO flag. In this case, the buffer should
    have the latest information, so setting the uptodate flag to the
    buffer (this avoids WARN_ON_ONCE() in mark_buffer_dirty().)

    According to this change, we would need to test BH_Write_EIO flag for
    the error checking. Currently nobody checks write I/O errors on
    metadata buffers, but it will be done in other patches I'm working on.

    Signed-off-by: Hidehiro Kawai <hidehiro.kawai.ez@hitachi.com>
    ---
    fs/ext3/inode.c | 10 ++++++++++
    1 file changed, 10 insertions(+)

    Index: linux-2.6.26-rc5-mm3/fs/ext3/inode.c
    ===================================================================
    --- linux-2.6.26-rc5-mm3.orig/fs/ext3/inode.c
    +++ linux-2.6.26-rc5-mm3/fs/ext3/inode.c
    @@ -2516,6 +2516,16 @@ static int __ext3_get_inode_loc(struct i
    }
    if (!buffer_uptodate(bh)) {
    lock_buffer(bh);
    +
    + /*
    + * If the buffer has the write error flag, we have failed
    + * to write out another inode in the same block. In this
    + * case, we don't have to read the block because we may
    + * read the old inode data successfully.
    + */
    + if (buffer_write_io_error(bh) && !buffer_uptodate(bh))
    + set_buffer_uptodate(bh);
    +
    if (buffer_uptodate(bh)) {
    /* someone brought it uptodate while we waited */
    unlock_buffer(bh);




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