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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>
This commit is contained in:
Liam Howlett 2021-06-28 19:38:50 -07:00 committed by Linus Torvalds
parent 2797e79f1a
commit ce6d42f2e4
1 changed files with 32 additions and 4 deletions
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36
include/linux/mm.h
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@ -2676,17 +2676,45 @@ 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);
struct vm_area_struct *vma = find_vma(mm, start_addr);
if (vma && end_addr <= vma->vm_start)
vma = NULL;
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;