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mm: abstract VMA merge and extend into vma_merge_extend() helper

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mremap uses vma_merge() in the case where a VMA needs to be extended. This
can be significantly simplified and abstracted.

This makes it far easier to understand what the actual function is doing,
avoids future mistakes in use of the confusing vma_merge() function and
importantly allows us to make future changes to how vma_merge() is
implemented by knowing explicitly which merge cases each invocation uses.

Note that in the mremap() extend case, we perform this merge only when
old_len == vma->vm_end - addr. The extension_start, i.e. the start of the
extended portion of the VMA is equal to addr + old_len, i.e. vma->vm_end.

With this refactoring, vma_merge() is no longer required anywhere except
mm/mmap.c, so mark it static.

Link: https://lkml.kernel.org/r/f16cbdc2e72d37a1a097c39dc7d1fee8919a1c93.1697043508.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>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Lorenzo Stoakes
2023-10-11 18:04:31 +01:00
committed by Andrew Morton
parent 4b5f2d2016
commit 93bf5d4aa2
3 changed files with 40 additions and 29 deletions
Download Patch File Download Diff File Expand all files Collapse all files

8
mm/internal.h
View File

@ -1005,11 +1005,9 @@ struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
/*
* mm/mmap.c
*/
struct vm_area_struct *vma_merge(struct vma_iterator *vmi,
struct mm_struct *, struct vm_area_struct *prev, unsigned long addr,
unsigned long end, unsigned long vm_flags, struct anon_vma *,
struct file *, pgoff_t, struct mempolicy *, struct vm_userfaultfd_ctx,
struct anon_vma_name *);
struct vm_area_struct *vma_merge_extend(struct vma_iterator *vmi,
struct vm_area_struct *vma,
unsigned long delta);
enum {
/* mark page accessed */