mm: Add a walk_page_mapping() function to the pagewalk code

For users that want to travers all page table entries pointing into a
region of a struct address_space mapping, introduce a walk_page_mapping()
function.

The walk_page_mapping() function will be initially be used for dirty-
tracking in virtual graphics drivers.

Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@surriel.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Huang Ying <ying.huang@intel.com>
Cc: Jérôme Glisse <jglisse@redhat.com>
Cc: Kirill A. Shutemov <kirill@shutemov.name>
Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Thomas Hellstrom 2019-10-01 11:17:34 +02:00
parent ace88f1018
commit ecaad8aca2
2 changed files with 102 additions and 1 deletions

View File

@ -24,6 +24,9 @@ struct mm_walk;
* "do page table walk over the current vma", returning
* a negative value means "abort current page table walk
* right now" and returning 1 means "skip the current vma"
* @pre_vma: if set, called before starting walk on a non-null vma.
* @post_vma: if set, called after a walk on a non-null vma, provided
* that @pre_vma and the vma walk succeeded.
*/
struct mm_walk_ops {
int (*pud_entry)(pud_t *pud, unsigned long addr,
@ -39,6 +42,9 @@ struct mm_walk_ops {
struct mm_walk *walk);
int (*test_walk)(unsigned long addr, unsigned long next,
struct mm_walk *walk);
int (*pre_vma)(unsigned long start, unsigned long end,
struct mm_walk *walk);
void (*post_vma)(struct mm_walk *walk);
};
/**
@ -62,5 +68,8 @@ int walk_page_range(struct mm_struct *mm, unsigned long start,
void *private);
int walk_page_vma(struct vm_area_struct *vma, const struct mm_walk_ops *ops,
void *private);
int walk_page_mapping(struct address_space *mapping, pgoff_t first_index,
pgoff_t nr, const struct mm_walk_ops *ops,
void *private);
#endif /* _LINUX_PAGEWALK_H */

View File

@ -254,13 +254,23 @@ static int __walk_page_range(unsigned long start, unsigned long end,
{
int err = 0;
struct vm_area_struct *vma = walk->vma;
const struct mm_walk_ops *ops = walk->ops;
if (vma && ops->pre_vma) {
err = ops->pre_vma(start, end, walk);
if (err)
return err;
}
if (vma && is_vm_hugetlb_page(vma)) {
if (walk->ops->hugetlb_entry)
if (ops->hugetlb_entry)
err = walk_hugetlb_range(start, end, walk);
} else
err = walk_pgd_range(start, end, walk);
if (vma && ops->post_vma)
ops->post_vma(walk);
return err;
}
@ -291,6 +301,11 @@ static int __walk_page_range(unsigned long start, unsigned long end,
* its vm_flags. walk_page_test() and @ops->test_walk() are used for this
* purpose.
*
* If operations need to be staged before and committed after a vma is walked,
* there are two callbacks, pre_vma() and post_vma(). Note that post_vma(),
* since it is intended to handle commit-type operations, can't return any
* errors.
*
* struct mm_walk keeps current values of some common data like vma and pmd,
* which are useful for the access from callbacks. If you want to pass some
* caller-specific data to callbacks, @private should be helpful.
@ -377,3 +392,80 @@ int walk_page_vma(struct vm_area_struct *vma, const struct mm_walk_ops *ops,
return err;
return __walk_page_range(vma->vm_start, vma->vm_end, &walk);
}
/**
* walk_page_mapping - walk all memory areas mapped into a struct address_space.
* @mapping: Pointer to the struct address_space
* @first_index: First page offset in the address_space
* @nr: Number of incremental page offsets to cover
* @ops: operation to call during the walk
* @private: private data for callbacks' usage
*
* This function walks all memory areas mapped into a struct address_space.
* The walk is limited to only the given page-size index range, but if
* the index boundaries cross a huge page-table entry, that entry will be
* included.
*
* Also see walk_page_range() for additional information.
*
* Locking:
* This function can't require that the struct mm_struct::mmap_sem is held,
* since @mapping may be mapped by multiple processes. Instead
* @mapping->i_mmap_rwsem must be held. This might have implications in the
* callbacks, and it's up tho the caller to ensure that the
* struct mm_struct::mmap_sem is not needed.
*
* Also this means that a caller can't rely on the struct
* vm_area_struct::vm_flags to be constant across a call,
* except for immutable flags. Callers requiring this shouldn't use
* this function.
*
* Return: 0 on success, negative error code on failure, positive number on
* caller defined premature termination.
*/
int walk_page_mapping(struct address_space *mapping, pgoff_t first_index,
pgoff_t nr, const struct mm_walk_ops *ops,
void *private)
{
struct mm_walk walk = {
.ops = ops,
.private = private,
};
struct vm_area_struct *vma;
pgoff_t vba, vea, cba, cea;
unsigned long start_addr, end_addr;
int err = 0;
lockdep_assert_held(&mapping->i_mmap_rwsem);
vma_interval_tree_foreach(vma, &mapping->i_mmap, first_index,
first_index + nr - 1) {
/* Clip to the vma */
vba = vma->vm_pgoff;
vea = vba + vma_pages(vma);
cba = first_index;
cba = max(cba, vba);
cea = first_index + nr;
cea = min(cea, vea);
start_addr = ((cba - vba) << PAGE_SHIFT) + vma->vm_start;
end_addr = ((cea - vba) << PAGE_SHIFT) + vma->vm_start;
if (start_addr >= end_addr)
continue;
walk.vma = vma;
walk.mm = vma->vm_mm;
err = walk_page_test(vma->vm_start, vma->vm_end, &walk);
if (err > 0) {
err = 0;
break;
} else if (err < 0)
break;
err = __walk_page_range(start_addr, end_addr, &walk);
if (err)
break;
}
return err;
}