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    SubjectRe: [RFC PATCH 1/3] fs: define new read_iter rwf flag
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    On Thu, 2017-09-28 at 06:54 -0700, Matthew Wilcox wrote:
    > 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.

    Me either!

    > Why not add a flag
    > to the kiocb ki_flags?
    >
    > #define IOCB_RWSEM_HELD (1 << 8)

    Thank you for the suggestion.

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