Commit ce6d42f2 authored Jun 28, 2021 by Liam Howlett Committed by Linus Torvalds Jun 29, 2021

mm: add vma_lookup(), update find_vma_intersection() comments

Patch series "mm: Add vma_lookup()", v2.

Many places in the kernel use find_vma() to get a vma and then check the
start address of the vma to ensure the next vma was not returned.

Other places use the find_vma_intersection() call with add, addr + 1 as
the range; looking for just the vma at a specific address.

The third use of find_vma() is by developers who do not know that the
function starts searching at the provided address upwards for the next
vma.  This results in a bug that is often overlooked for a long time.

Adding the new vma_lookup() function will allow for cleaner code by
removing the find_vma() calls which check limits, making
find_vma_intersection() calls of a single address to be shorter, and
potentially reduce the incorrect uses of find_vma().

This patch (of 22):

Many places in the kernel use find_vma() to get a vma and then check the
start address of the vma to ensure the next vma was not returned.

Other places use the find_vma_intersection() call with add, addr + 1 as
the range; looking for just the vma at a specific address.

The third use of find_vma() is by developers who do not know that the
function starts searching at the provided address upwards for the next
vma.  This results in a bug that is often overlooked for a long time.

Adding the new vma_lookup() function will allow for cleaner code by
removing the find_vma() calls which check limits, making
find_vma_intersection() calls of a single address to be shorter, and
potentially reduce the incorrect uses of find_vma().

Also change find_vma_intersection() comments and declaration to be of the
correct length and add kernel documentation style comment.

Link: https://lkml.kernel.org/r/20210521174745.2219620-1-Liam.Howlett@Oracle.com
Link: https://lkml.kernel.org/r/20210521174745.2219620-2-Liam.Howlett@Oracle.com


Signed-off-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
Reviewed-by: Laurent Dufour <ldufour@linux.ibm.com>
Acked-by: David Hildenbrand <david@redhat.com>
Acked-by: Davidlohr Bueso <dbueso@suse.de>
Cc: David Miller <davem@davemloft.net>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 2797e79f

include/linux/mm.h

+32 −4

Original line number	Diff line number	Diff line
		@@ -2676,9 +2676,19 @@ extern struct vm_area_struct * find_vma(struct mm_struct * mm, unsigned long add
		extern struct vm_area_struct * find_vma_prev(struct mm_struct * mm, unsigned long addr,
		struct vm_area_struct **pprev);

		/* Look up the first VMA which intersects the interval start_addr..end_addr-1,
		NULL if none. Assume start_addr < end_addr. */
		static inline struct vm_area_struct * find_vma_intersection(struct mm_struct * mm, unsigned long start_addr, unsigned long end_addr)
		/**
		* find_vma_intersection() - Look up the first VMA which intersects the interval
		* @mm: The process address space.
		* @start_addr: The inclusive start user address.
		* @end_addr: The exclusive end user address.
		*
		* Returns: The first VMA within the provided range, %NULL otherwise. Assumes
		* start_addr < end_addr.
		*/
		static inline
		struct vm_area_struct find_vma_intersection(struct mm_struct mm,
		unsigned long start_addr,
		unsigned long end_addr)
		{
		struct vm_area_struct *vma = find_vma(mm, start_addr);

		@@ -2687,6 +2697,24 @@ static inline struct vm_area_struct * find_vma_intersection(struct mm_struct * m
		return vma;
		}

		/**
		* vma_lookup() - Find a VMA at a specific address
		* @mm: The process address space.
		* @addr: The user address.
		*
		* Return: The vm_area_struct at the given address, %NULL otherwise.
		*/
		static inline
		struct vm_area_struct vma_lookup(struct mm_struct mm, unsigned long addr)
		{
		struct vm_area_struct *vma = find_vma(mm, addr);

		if (vma && addr < vma->vm_start)
		vma = NULL;

		return vma;
		}

		static inline unsigned long vm_start_gap(struct vm_area_struct *vma)
		{
		unsigned long vm_start = vma->vm_start;