3657fdc245
Patch series "Abstract vma_merge() and split_vma()", v4. The vma_merge() interface is very confusing and its implementation has led to numerous bugs as a result of that confusion. In addition there is duplication both in invocation of vma_merge(), but also in the common mprotect()-style pattern of attempting a merge, then if this fails, splitting the portion of a VMA about to have its attributes changed. This pattern has been copy/pasted around the kernel in each instance where such an operation has been required, each very slightly modified from the last to make it even harder to decipher what is going on. Simplify the whole thing by dividing the actual uses of vma_merge() and split_vma() into specific and abstracted functions and de-duplicate the vma_merge()/split_vma() pattern altogether. Doing so also opens the door to changing how vma_merge() is implemented - by knowing precisely what cases a caller is invoking rather than having a central interface where anything might happen we can untangle the brittle and confusing vma_merge() implementation into something more workable. For mprotect()-like cases we introduce vma_modify() which performs the vma_merge()/split_vma() pattern, returning a pointer to either the merged or split VMA or an ERR_PTR(err) if the splits fail. We provide a number of inline helper functions to make things even clearer:- * vma_modify_flags() - Prepare to modify the VMA's flags. * vma_modify_flags_name() - Prepare to modify the VMA's flags/anon_vma_name * vma_modify_policy() - Prepare to modify the VMA's mempolicy. * vma_modify_flags_uffd() - Prepare to modify the VMA's flags/uffd context. For cases where a new VMA is attempted to be merged with adjacent VMAs we add:- * vma_merge_new_vma() - Prepare to merge a new VMA. * vma_merge_extend() - Prepare to extend the end of a new VMA. This patch (of 5): The vma_policy() define is a helper specifically for a VMA field so it makes sense to host it in the memory management types header. The anon_vma_name(), anon_vma_name_alloc() and anon_vma_name_free() functions are a little out of place in mm_inline.h as they define external functions, and so it makes sense to locate them in mm_types.h. The purpose of these relocations is to make it possible to abstract static inline wrappers which invoke both of these helpers. Link: https://lkml.kernel.org/r/cover.1697043508.git.lstoakes@gmail.com Link: https://lkml.kernel.org/r/24bfc6c9e382fffbcb0ea8d424392c27d56cc8ca.1697043508.git.lstoakes@gmail.com Signed-off-by: Lorenzo Stoakes <lstoakes@gmail.com> Reviewed-by: Vlastimil Babka <vbabka@suse.cz> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: Christian Brauner <brauner@kernel.org> Cc: Liam R. Howlett <Liam.Howlett@oracle.com> Cc: Lorenzo Stoakes <lstoakes@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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README
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.