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Subject[PATCH 0/4] IMA: making i_readcount a first class inode citizen
Date
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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