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Currently, the binder driver always uses the mmap lock to make changes to
its vma. Because the mmap lock is global to the process, this can involve
significant contention. However, the kernel has a feature called per-vma
locks, which can significantly reduce contention. For example, you can
take a vma lock in parallel with an mmap write lock. This is important
because contention on the mmap lock has been a long-term recurring
challenge for the Binder driver.
This patch introduces support for using `lock_vma_under_rcu` from Rust.
The Rust Binder driver will be able to use this to reduce contention on
the mmap lock.
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Alice Ryhl <[email protected]>
Acked-by: Lorenzo Stoakes <[email protected]>
Acked-by: Liam R. Howlett <[email protected]>
Reviewed-by: Jann Horn <[email protected]>
Reviewed-by: Andreas Hindborg <[email protected]>
Reviewed-by: Gary Guo <[email protected]>
Cc: Alex Gaynor <[email protected]>
Cc: Arnd Bergmann <[email protected]>
Cc: Balbir Singh <[email protected]>
Cc: Benno Lossin <[email protected]>
Cc: Björn Roy Baron <[email protected]>
Cc: Boqun Feng <[email protected]>
Cc: Greg Kroah-Hartman <[email protected]>
Cc: John Hubbard <[email protected]>
Cc: Matthew Wilcox (Oracle) <[email protected]>
Cc: Miguel Ojeda <[email protected]>
Cc: Suren Baghdasaryan <[email protected]>
Cc: Trevor Gross <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
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This adds a type called VmaRef which is used when referencing a vma that
you have read access to. Here, read access means that you hold either the
mmap read lock or the vma read lock (or stronger).
Additionally, a vma_lookup method is added to the mmap read guard, which
enables you to obtain a &VmaRef in safe Rust code.
This patch only provides a way to lock the mmap read lock, but a follow-up
patch also provides a way to just lock the vma read lock.
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Alice Ryhl <[email protected]>
Acked-by: Lorenzo Stoakes <[email protected]>
Acked-by: Liam R. Howlett <[email protected]>
Reviewed-by: Jann Horn <[email protected]>
Reviewed-by: Andreas Hindborg <[email protected]>
Reviewed-by: Gary Guo <[email protected]>
Cc: Alex Gaynor <[email protected]>
Cc: Arnd Bergmann <[email protected]>
Cc: Balbir Singh <[email protected]>
Cc: Benno Lossin <[email protected]>
Cc: Björn Roy Baron <[email protected]>
Cc: Boqun Feng <[email protected]>
Cc: Greg Kroah-Hartman <[email protected]>
Cc: John Hubbard <[email protected]>
Cc: Matthew Wilcox (Oracle) <[email protected]>
Cc: Miguel Ojeda <[email protected]>
Cc: Suren Baghdasaryan <[email protected]>
Cc: Trevor Gross <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
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Patch series "Rust support for mm_struct, vm_area_struct, and mmap", v16.
This updates the vm_area_struct support to use the approach we discussed
at LPC where there are several different Rust wrappers for vm_area_struct
depending on the kind of access you have to the vma. Each case allows a
different set of operations on the vma.
This includes an MM MAINTAINERS entry as proposed by Lorenzo:
https://lore.kernel.org/all/[email protected]/
This patch (of 9):
These abstractions allow you to reference a `struct mm_struct` using both
mmgrab and mmget refcounts. This is done using two Rust types:
* Mm - represents an mm_struct where you don't know anything about the
value of mm_users.
* MmWithUser - represents an mm_struct where you know at compile time
that mm_users is non-zero.
This allows us to encode in the type system whether a method requires that
mm_users is non-zero or not. For instance, you can always call
`mmget_not_zero` but you can only call `mmap_read_lock` when mm_users is
non-zero.
The struct is called Mm to keep consistency with the C side.
The ability to obtain `current->mm` is added later in this series.
The mm module is defined to only exist when CONFIG_MMU is set. This
avoids various errors due to missing types and functions when CONFIG_MMU
is disabled. More fine-grained cfgs can be considered in the future. See
the thread at [1] for more info.
Link: https://lkml.kernel.org/r/[email protected]
Link: https://lkml.kernel.org/r/[email protected]
Link: https://lore.kernel.org/all/[email protected]/
Signed-off-by: Alice Ryhl <[email protected]>
Acked-by: Lorenzo Stoakes <[email protected]>
Acked-by: Liam R. Howlett <[email protected]>
Acked-by: Balbir Singh <[email protected]>
Reviewed-by: Andreas Hindborg <[email protected]>
Reviewed-by: Gary Guo <[email protected]>
Cc: Alex Gaynor <[email protected]>
Cc: Arnd Bergmann <[email protected]>
Cc: Benno Lossin <[email protected]>
Cc: Björn Roy Baron <[email protected]>
Cc: Boqun Feng <[email protected]>
Cc: Greg Kroah-Hartman <[email protected]>
Cc: Jann Horn <[email protected]>
Cc: John Hubbard <[email protected]>
Cc: Matthew Wilcox (Oracle) <[email protected]>
Cc: Miguel Ojeda <[email protected]>
Cc: Suren Baghdasaryan <[email protected]>
Cc: Trevor Gross <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
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