[RFC PATCH 1/3] fs: define new read_iter rwf flag
willy at infradead.org
Thu Sep 28 13:54:16 UTC 2017
On Thu, Sep 28, 2017 at 08:39:31AM -0400, Mimi Zohar wrote:
> Writing extended attributes requires exclusively taking the i_rwsem
> lock. To synchronize the file hash calculation and writing the file
> hash as security.ima xattr, IMA-appraisal takes the i_rwsem lock
> exclusively before calculating the file hash. (Once the file hash
> is calculated, the result is cached. Taking the lock exclusively
> prevents calculating the file hash multiple times.)
> Some filesystems have recently replaced their filesystem dependent
> lock with the global i_rwsem to read a file. As a result, when IMA
> attempts to calculate the file hash, reading the file attempts to
> take the i_rwsem again.
> To resolve this problem, this patch defines a new read_iter flag
> named "rwf" to indicate that the i_rwsem has already been taken
> exclusively. Subsequent patches will set or test the "rwf" flag.
I don't like adding a bool parameter everywhere. Why not add a flag
to the kiocb ki_flags?
#define IOCB_RWSEM_HELD (1 << 8)
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