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    Subject[26/34] ext4: Avoid data / filesystem corruption when write fails to copy data
    2.6.32-stable review patch.  If anyone has any objections, please let us know.

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

    (cherry picked from commit b9a4207d5e911b938f73079a83cc2ae10524ec7f)

    When ext4_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 the 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.

    Signed-off-by: Jan Kara <jack@suse.cz>
    Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
    Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
    ---
    fs/ext4/inode.c | 20 +++++++++++++++-----
    1 file changed, 15 insertions(+), 5 deletions(-)

    --- a/fs/ext4/inode.c
    +++ b/fs/ext4/inode.c
    @@ -1534,6 +1534,16 @@ static int do_journal_get_write_access(h
    return ext4_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 ext4_truncate_failed_write(struct inode *inode)
    +{
    + truncate_inode_pages(inode->i_mapping, inode->i_size);
    + ext4_truncate(inode);
    +}
    +
    static int ext4_write_begin(struct file *file, struct address_space *mapping,
    loff_t pos, unsigned len, unsigned flags,
    struct page **pagep, void **fsdata)
    @@ -1599,7 +1609,7 @@ retry:

    ext4_journal_stop(handle);
    if (pos + len > inode->i_size) {
    - ext4_truncate(inode);
    + ext4_truncate_failed_write(inode);
    /*
    * If truncate failed early the inode might
    * still be on the orphan list; we need to
    @@ -1709,7 +1719,7 @@ static int ext4_ordered_write_end(struct
    ret = ret2;

    if (pos + len > inode->i_size) {
    - ext4_truncate(inode);
    + ext4_truncate_failed_write(inode);
    /*
    * If truncate failed early the inode might still be
    * on the orphan list; we need to make sure the inode
    @@ -1751,7 +1761,7 @@ static int ext4_writeback_write_end(stru
    ret = ret2;

    if (pos + len > inode->i_size) {
    - ext4_truncate(inode);
    + ext4_truncate_failed_write(inode);
    /*
    * If truncate failed early the inode might still be
    * on the orphan list; we need to make sure the inode
    @@ -1814,7 +1824,7 @@ static int ext4_journalled_write_end(str
    if (!ret)
    ret = ret2;
    if (pos + len > inode->i_size) {
    - ext4_truncate(inode);
    + ext4_truncate_failed_write(inode);
    /*
    * If truncate failed early the inode might still be
    * on the orphan list; we need to make sure the inode
    @@ -3091,7 +3101,7 @@ retry:
    * i_size_read because we hold i_mutex.
    */
    if (pos + len > inode->i_size)
    - ext4_truncate(inode);
    + ext4_truncate_failed_write(inode);
    }

    if (ret == -ENOSPC && ext4_should_retry_alloc(inode->i_sb, &retries))



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