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    Subject[81/90] ext3: Fix data / filesystem corruption when write fails to copy data
    2.6.31-stable review patch.  If anyone has any objections, please let us know.

    ------------------

    From: Jan Kara <jack@suse.cz>

    commit 68eb3db08344286733adac48304d9fb7a0e53b27 upstream.

    When ext3_write_begin fails after allocating some blocks or
    generic_perform_write fails to copy data to write, we truncate blocks already
    instantiated beyond i_size. Although these blocks were never inside i_size, we
    have to truncate pagecache of these blocks so that corresponding buffers get
    unmapped. Otherwise subsequent __block_prepare_write (called because we are
    retrying the write) will find the buffers mapped, not call ->get_block, and
    thus the page will be backed by already freed blocks leading to filesystem and
    data corruption.

    Reported-by: James Y Knight <foom@fuhm.net>
    Signed-off-by: Jan Kara <jack@suse.cz>
    Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

    ---
    fs/ext3/inode.c | 18 ++++++++++++++----
    1 file changed, 14 insertions(+), 4 deletions(-)

    --- a/fs/ext3/inode.c
    +++ b/fs/ext3/inode.c
    @@ -1137,6 +1137,16 @@ static int do_journal_get_write_access(h
    return ext3_journal_get_write_access(handle, bh);
    }

    +/*
    + * Truncate blocks that were not used by write. We have to truncate the
    + * pagecache as well so that corresponding buffers get properly unmapped.
    + */
    +static void ext3_truncate_failed_write(struct inode *inode)
    +{
    + truncate_inode_pages(inode->i_mapping, inode->i_size);
    + ext3_truncate(inode);
    +}
    +
    static int ext3_write_begin(struct file *file, struct address_space *mapping,
    loff_t pos, unsigned len, unsigned flags,
    struct page **pagep, void **fsdata)
    @@ -1195,7 +1205,7 @@ write_begin_failed:
    unlock_page(page);
    page_cache_release(page);
    if (pos + len > inode->i_size)
    - ext3_truncate(inode);
    + ext3_truncate_failed_write(inode);
    }
    if (ret == -ENOSPC && ext3_should_retry_alloc(inode->i_sb, &retries))
    goto retry;
    @@ -1290,7 +1300,7 @@ static int ext3_ordered_write_end(struct
    page_cache_release(page);

    if (pos + len > inode->i_size)
    - ext3_truncate(inode);
    + ext3_truncate_failed_write(inode);
    return ret ? ret : copied;
    }

    @@ -1316,7 +1326,7 @@ static int ext3_writeback_write_end(stru
    page_cache_release(page);

    if (pos + len > inode->i_size)
    - ext3_truncate(inode);
    + ext3_truncate_failed_write(inode);
    return ret ? ret : copied;
    }

    @@ -1369,7 +1379,7 @@ static int ext3_journalled_write_end(str
    page_cache_release(page);

    if (pos + len > inode->i_size)
    - ext3_truncate(inode);
    + ext3_truncate_failed_write(inode);
    return ret ? ret : copied;
    }




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