diff options
| -rw-r--r-- | mm/hugetlb.c | 52 |
1 files changed, 50 insertions, 2 deletions
diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 10de25cf1f99..4a1d7021efaf 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -217,8 +217,20 @@ static inline struct hugepage_subpool *subpool_vma(struct vm_area_struct *vma) * Region tracking -- allows tracking of reservations and instantiated pages * across the pages in a mapping. * - * The region data structures are embedded into a resv_map and - * protected by a resv_map's lock + * The region data structures are embedded into a resv_map and protected + * by a resv_map's lock. The set of regions within the resv_map represent + * reservations for huge pages, or huge pages that have already been + * instantiated within the map. The from and to elements are huge page + * indicies into the associated mapping. from indicates the starting index + * of the region. to represents the first index past the end of the region. + * + * For example, a file region structure with from == 0 and to == 4 represents + * four huge pages in a mapping. It is important to note that the to element + * represents the first element past the end of the region. This is used in + * arithmetic as 4(to) - 0(from) = 4 huge pages in the region. + * + * Interval notation of the form [from, to) will be used to indicate that + * the endpoint from is inclusive and to is exclusive. */ struct file_region { struct list_head link; @@ -226,6 +238,14 @@ struct file_region { long to; }; +/* + * Add the huge page range represented by [f, t) to the reserve + * map. Existing regions will be expanded to accommodate the + * specified range. We know only existing regions need to be + * expanded, because region_add is only called after region_chg + * with the same range. If a new file_region structure must + * be allocated, it is done in region_chg. + */ static long region_add(struct resv_map *resv, long f, long t) { struct list_head *head = &resv->regions; @@ -265,6 +285,25 @@ static long region_add(struct resv_map *resv, long f, long t) return 0; } +/* + * Examine the existing reserve map and determine how many + * huge pages in the specified range [f, t) are NOT currently + * represented. This routine is called before a subsequent + * call to region_add that will actually modify the reserve + * map to add the specified range [f, t). region_chg does + * not change the number of huge pages represented by the + * map. However, if the existing regions in the map can not + * be expanded to represent the new range, a new file_region + * structure is added to the map as a placeholder. This is + * so that the subsequent region_add call will have all the + * regions it needs and will not fail. + * + * Returns the number of huge pages that need to be added + * to the existing reservation map for the range [f, t). + * This number is greater or equal to zero. -ENOMEM is + * returned if a new file_region structure is needed and can + * not be allocated. + */ static long region_chg(struct resv_map *resv, long f, long t) { struct list_head *head = &resv->regions; @@ -331,6 +370,11 @@ out_nrg: return chg; } +/* + * Truncate the reserve map at index 'end'. Modify/truncate any + * region which contains end. Delete any regions past end. + * Return the number of huge pages removed from the map. + */ static long region_truncate(struct resv_map *resv, long end) { struct list_head *head = &resv->regions; @@ -366,6 +410,10 @@ out: return chg; } +/* + * Count and return the number of huge pages in the reserve map + * that intersect with the range [f, t). + */ static long region_count(struct resv_map *resv, long f, long t) { struct list_head *head = &resv->regions; |