fallocate hole punch will want to remove a specific range of pages.
The existing region_truncate() routine deletes all region/reserve
map entries after a specified offset. region_del() will provide
this same functionality if the end of region is specified as LONG_MAX.
Hence, region_del() can replace region_truncate().
Unlike region_truncate(), region_del() can return an error in the
rare case where it can not allocate memory for a region descriptor.
This ONLY happens in the case where an existing region must be split.
Current callers passing LONG_MAX as end of range will never experience
this error and do not need to deal with error handling. Future
callers of region_del() (such as fallocate hole punch) will need to
handle this error.
Signed-off-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
---
mm/hugetlb.c | 122 +++++++++++++++++++++++++++++++++++++++++------------------
1 file changed, 85 insertions(+), 37 deletions(-)
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index c3923a1..a573396 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -462,43 +462,90 @@ static void region_abort(struct resv_map *resv, long f, long t)
}
/*
- * 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.
+ * Delete the specified range [f, t) from the reserve map. If the
+ * t parameter is LONG_MAX, this indicates that ALL regions after f
+ * should be deleted. Locate the regions which intersect [f, t)
+ * and either trim, delete or split the existing regions.
+ *
+ * Returns the number of huge pages deleted from the reserve map.
+ * In the normal case, the return value is zero or more. In the
+ * case where a region must be split, a new region descriptor must
+ * be allocated. If the allocation fails, -ENOMEM will be returned.
+ * NOTE: If the parameter t == LONG_MAX, then we will never split
+ * a region and possibly return -ENOMEM. Callers specifying
+ * t == LONG_MAX do not need to check for -ENOMEM error.
*/
-static long region_truncate(struct resv_map *resv, long end)
+static long region_del(struct resv_map *resv, long f, long t)
{
struct list_head *head = &resv->regions;
struct file_region *rg, *trg;
- long chg = 0;
+ struct file_region *nrg = NULL;
+ long del = 0;
+retry:
spin_lock(&resv->lock);
- /* Locate the region we are either in or before. */
- list_for_each_entry(rg, head, link)
- if (end <= rg->to)
+ list_for_each_entry_safe(rg, trg, head, link) {
+ if (rg->to <= f)
+ continue;
+ if (rg->from >= t)
break;
- if (&rg->link == head)
- goto out;
- /* If we are in the middle of a region then adjust it. */
- if (end > rg->from) {
- chg = rg->to - end;
- rg->to = end;
- rg = list_entry(rg->link.next, typeof(*rg), link);
- }
+ if (f > rg->from && t < rg->to) { /* Must split region */
+ /*
+ * Check for an entry in the cache before dropping
+ * lock and attempting allocation.
+ */
+ if (!nrg &&
+ resv->rgn_cache_count > resv->adds_in_progress) {
+ nrg = list_first_entry(&resv->rgn_cache,
+ struct file_region,
+ link);
+ list_del(&nrg->link);
+ resv->rgn_cache_count--;
+ }
- /* Drop any remaining regions. */
- list_for_each_entry_safe(rg, trg, rg->link.prev, link) {
- if (&rg->link == head)
+ if (!nrg) {
+ spin_unlock(&resv->lock);
+ nrg = kmalloc(sizeof(*nrg), GFP_KERNEL);
+ if (!nrg)
+ return -ENOMEM;
+ goto retry;
+ }
+
+ del += t - f;
+
+ /* New entry for end of split region */
+ nrg->from = t;
+ nrg->to = rg->to;
+ INIT_LIST_HEAD(&nrg->link);
+
+ /* Original entry is trimmed */
+ rg->to = f;
+
+ list_add(&nrg->link, &rg->link);
+ nrg = NULL;
break;
- chg += rg->to - rg->from;
- list_del(&rg->link);
- kfree(rg);
+ }
+
+ if (f <= rg->from && t >= rg->to) { /* Remove entire region */
+ del += rg->to - rg->from;
+ list_del(&rg->link);
+ kfree(rg);
+ continue;
+ }
+
+ if (f <= rg->from) { /* Trim beginning of region */
+ del += t - rg->from;
+ rg->from = t;
+ } else { /* Trim end of region */
+ del += rg->to - f;
+ rg->to = f;
+ }
}
-out:
spin_unlock(&resv->lock);
- return chg;
+ kfree(nrg);
+ return del;
}
/*
@@ -649,7 +696,7 @@ void resv_map_release(struct kref *ref)
struct file_region *rg, *trg;
/* Clear out any active regions before we release the map. */
- region_truncate(resv_map, 0);
+ region_del(resv_map, 0, LONG_MAX);
/* ... and any entries left in the cache */
list_for_each_entry_safe(rg, trg, head, link) {
@@ -1574,7 +1621,7 @@ static void return_unused_surplus_pages(struct hstate *h,
/*
- * vma_needs_reservation, vma_commit_reservation and vma_abort_reservation
+ * vma_needs_reservation, vma_commit_reservation and vma_end_reservation
* are used by the huge page allocation routines to manage reservations.
*
* vma_needs_reservation is called to determine if the huge page at addr
@@ -1582,8 +1629,9 @@ static void return_unused_surplus_pages(struct hstate *h,
* needed, the value 1 is returned. The caller is then responsible for
* managing the global reservation and subpool usage counts. After
* the huge page has been allocated, vma_commit_reservation is called
- * to add the page to the reservation map. If the reservation must be
- * aborted instead of committed, vma_abort_reservation is called.
+ * to add the page to the reservation map. If the page allocation fails,
+ * the reservation must be ended instead of committed. vma_end_reservation
+ * is called in such cases.
*
* In the normal case, vma_commit_reservation returns the same value
* as the preceding vma_needs_reservation call. The only time this
@@ -1594,7 +1642,7 @@ static void return_unused_surplus_pages(struct hstate *h,
enum vma_resv_mode {
VMA_NEEDS_RESV,
VMA_COMMIT_RESV,
- VMA_ABORT_RESV,
+ VMA_END_RESV,
};
static long __vma_reservation_common(struct hstate *h,
struct vm_area_struct *vma, unsigned long addr,
@@ -1616,7 +1664,7 @@ static long __vma_reservation_common(struct hstate *h,
case VMA_COMMIT_RESV:
ret = region_add(resv, idx, idx + 1);
break;
- case VMA_ABORT_RESV:
+ case VMA_END_RESV:
region_abort(resv, idx, idx + 1);
ret = 0;
break;
@@ -1642,10 +1690,10 @@ static long vma_commit_reservation(struct hstate *h,
return __vma_reservation_common(h, vma, addr, VMA_COMMIT_RESV);
}
-static void vma_abort_reservation(struct hstate *h,
+static void vma_end_reservation(struct hstate *h,
struct vm_area_struct *vma, unsigned long addr)
{
- (void)__vma_reservation_common(h, vma, addr, VMA_ABORT_RESV);
+ (void)__vma_reservation_common(h, vma, addr, VMA_END_RESV);
}
static struct page *alloc_huge_page(struct vm_area_struct *vma,
@@ -1672,7 +1720,7 @@ static struct page *alloc_huge_page(struct vm_area_struct *vma,
return ERR_PTR(-ENOMEM);
if (chg || avoid_reserve)
if (hugepage_subpool_get_pages(spool, 1) < 0) {
- vma_abort_reservation(h, vma, addr);
+ vma_end_reservation(h, vma, addr);
return ERR_PTR(-ENOSPC);
}
@@ -1720,7 +1768,7 @@ out_uncharge_cgroup:
out_subpool_put:
if (chg || avoid_reserve)
hugepage_subpool_put_pages(spool, 1);
- vma_abort_reservation(h, vma, addr);
+ vma_end_reservation(h, vma, addr);
return ERR_PTR(-ENOSPC);
}
@@ -3367,7 +3415,7 @@ retry:
goto backout_unlocked;
}
/* Just decrements count, does not deallocate */
- vma_abort_reservation(h, vma, address);
+ vma_end_reservation(h, vma, address);
}
ptl = huge_pte_lockptr(h, mm, ptep);
@@ -3516,7 +3564,7 @@ int hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
goto out_mutex;
}
/* Just decrements count, does not deallocate */
- vma_abort_reservation(h, vma, address);
+ vma_end_reservation(h, vma, address);
if (!(vma->vm_flags & VM_MAYSHARE))
pagecache_page = hugetlbfs_pagecache_page(h,
@@ -3872,7 +3920,7 @@ void hugetlb_unreserve_pages(struct inode *inode, long offset, long freed)
long gbl_reserve;
if (resv_map)
- chg = region_truncate(resv_map, offset);
+ chg = region_del(resv_map, offset, LONG_MAX);
spin_lock(&inode->i_lock);
inode->i_blocks -= (blocks_per_huge_page(h) * freed);
spin_unlock(&inode->i_lock);
--
2.1.0
--
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