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    Subject[PATCH 3.18 47/60] udf: Fix deadlock between writeback and udf_setsize()
    Date
    3.18-stable review patch.  If anyone has any objections, please let me know.

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

    From: Jan Kara <jack@suse.cz>

    commit f2e95355891153f66d4156bf3a142c6489cd78c6 upstream.

    udf_setsize() called truncate_setsize() with i_data_sem held. Thus
    truncate_pagecache() called from truncate_setsize() could lock a page
    under i_data_sem which can deadlock as page lock ranks below
    i_data_sem - e. g. writeback can hold page lock and try to acquire
    i_data_sem to map a block.

    Fix the problem by moving truncate_setsize() calls from under
    i_data_sem. It is safe for us to change i_size without holding
    i_data_sem as all the places that depend on i_size being stable already
    hold inode_lock.

    Fixes: 7e49b6f2480cb9a9e7322a91592e56a5c85361f5
    Signed-off-by: Jan Kara <jack@suse.cz>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    fs/udf/inode.c | 4 ++--
    1 file changed, 2 insertions(+), 2 deletions(-)

    --- a/fs/udf/inode.c
    +++ b/fs/udf/inode.c
    @@ -1237,8 +1237,8 @@ int udf_setsize(struct inode *inode, lof
    return err;
    }
    set_size:
    - truncate_setsize(inode, newsize);
    up_write(&iinfo->i_data_sem);
    + truncate_setsize(inode, newsize);
    } else {
    if (iinfo->i_alloc_type == ICBTAG_FLAG_AD_IN_ICB) {
    down_write(&iinfo->i_data_sem);
    @@ -1255,9 +1255,9 @@ set_size:
    udf_get_block);
    if (err)
    return err;
    + truncate_setsize(inode, newsize);
    down_write(&iinfo->i_data_sem);
    udf_clear_extent_cache(inode);
    - truncate_setsize(inode, newsize);
    udf_truncate_extents(inode);
    up_write(&iinfo->i_data_sem);
    }

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