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 | 99 ++++++++++++++++++++++++++++++++++++++++++++----------------
1 file changed, 73 insertions(+), 26 deletions(-)
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index de03374..1b21fb7 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -460,43 +460,90 @@ 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;
}
/*
@@ -647,7 +694,7 @@ 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) {
@@ -3870,7 +3917,7 @@ 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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