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    Subject[PATCH 0/4] IMA: making i_readcount a first class inode citizen
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    On Mon, 2010-10-25 at 14:41 -0400, Eric Paris wrote:

    <snip>

    > I believe that IBM is going to look into making i_readcount a first
    > class citizen which can be used by both IMA and generic_setlease().
    > Then people could say IMA had 0 per inode overhead :)

    This patchset separates the incrementing/decrementing of the i_readcount,
    in the VFS layer, from other IMA functionality, by replacing the current
    ima_counts_get() call with iget_readcount(). Its unclear whether this
    call to increment i_readcount should be made earlier.

    The patch ordering is a bit redundant in order to leave removing the ifdef
    around i_readcount until the last patch. The first three patches: defines
    iget/iput_readcount(), moves the IMA functionality in ima_counts_get() to
    ima_file_check(), and removes the IMA imbalance code, simplifying IMA. The
    last patch moves iget/iput_readcount() to the fs directory and removes the
    ifdef around i_readcount, making i_readcount into a "first class inode citizen".

    The generic_setlease code could then take advantage of i_readcount, assuming
    it can take the spin_lock, by doing something like:

    - if ((arg == F_RDLCK) && (atomic_read(&inode->i_writecount) > 0))
    +
    + spin_lock(&inode->i_lock);
    + if ((arg == F_RDLCK) && (atomic_read(&inode->i_writecount) > 0)){
    + spin_unlock(&inode->i_lock);
    goto out;
    - if ((arg == F_WRLCK)
    - && ((atomic_read(&dentry->d_count) > 1)
    - || (atomic_read(&inode->i_count) > 1)))
    + }
    + if ((arg == F_WRLCK) && (inode->i_readcount > 1)) {
    + spin_unlock(&inode->i_lock);
    goto out;
    + }
    + spin_unlock(&inode->i_lock);
    }

    Mimi

    Mimi Zohar (4):
    IMA: define readcount functions
    IMA: maintain i_readcount in the VFS layer
    IMA: remove IMA imbalance checking
    IMA: making i_readcount a first class inode citizen

    fs/file_table.c | 23 +++++++-
    fs/inode.c | 3 +
    fs/open.c | 3 +-
    include/linux/fs.h | 4 +-
    include/linux/ima.h | 6 --
    security/integrity/ima/ima_iint.c | 5 --
    security/integrity/ima/ima_main.c | 125 ++++--------------------------------
    7 files changed, 43 insertions(+), 126 deletions(-)

    --
    1.7.2.2



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