Merge https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net

Signed-off-by: Jakub Kicinski <kuba@kernel.org>

1 files changed, 5 insertions, 85 deletions

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 5a620f690911..37f15c3c24dc 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -1568,103 +1568,23 @@ int PageHeadHuge(struct page *page_head)
 }
 
 /*
- * Find address_space associated with hugetlbfs page.
- * Upon entry page is locked and page 'was' mapped although mapped state
- * could change.  If necessary, use anon_vma to find vma and associated
- * address space.  The returned mapping may be stale, but it can not be
- * invalid as page lock (which is held) is required to destroy mapping.
- */
-static struct address_space *_get_hugetlb_page_mapping(struct page *hpage)
-{
-	struct anon_vma *anon_vma;
-	pgoff_t pgoff_start, pgoff_end;
-	struct anon_vma_chain *avc;
-	struct address_space *mapping = page_mapping(hpage);
-
-	/* Simple file based mapping */
-	if (mapping)
-		return mapping;
-
-	/*
-	 * Even anonymous hugetlbfs mappings are associated with an
-	 * underlying hugetlbfs file (see hugetlb_file_setup in mmap
-	 * code).  Find a vma associated with the anonymous vma, and
-	 * use the file pointer to get address_space.
-	 */
-	anon_vma = page_lock_anon_vma_read(hpage);
-	if (!anon_vma)
-		return mapping;  /* NULL */
-
-	/* Use first found vma */
-	pgoff_start = page_to_pgoff(hpage);
-	pgoff_end = pgoff_start + pages_per_huge_page(page_hstate(hpage)) - 1;
-	anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root,
-					pgoff_start, pgoff_end) {
-		struct vm_area_struct *vma = avc->vma;
-
-		mapping = vma->vm_file->f_mapping;
-		break;
-	}
-
-	anon_vma_unlock_read(anon_vma);
-	return mapping;
-}
-
-/*
  * Find and lock address space (mapping) in write mode.
  *
- * Upon entry, the page is locked which allows us to find the mapping
- * even in the case of an anon page.  However, locking order dictates
- * the i_mmap_rwsem be acquired BEFORE the page lock.  This is hugetlbfs
- * specific.  So, we first try to lock the sema while still holding the
- * page lock.  If this works, great!  If not, then we need to drop the
- * page lock and then acquire i_mmap_rwsem and reacquire page lock.  Of
- * course, need to revalidate state along the way.
+ * Upon entry, the page is locked which means that page_mapping() is
+ * stable.  Due to locking order, we can only trylock_write.  If we can
+ * not get the lock, simply return NULL to caller.
  */
 struct address_space *hugetlb_page_mapping_lock_write(struct page *hpage)
 {
-	struct address_space *mapping, *mapping2;
+	struct address_space *mapping = page_mapping(hpage);
 
-	mapping = _get_hugetlb_page_mapping(hpage);
-retry:
 	if (!mapping)
 		return mapping;
 
-	/*
-	 * If no contention, take lock and return
-	 */
 	if (i_mmap_trylock_write(mapping))
 		return mapping;
 
-	/*
-	 * Must drop page lock and wait on mapping sema.
-	 * Note:  Once page lock is dropped, mapping could become invalid.
-	 * As a hack, increase map count until we lock page again.
-	 */
-	atomic_inc(&hpage->_mapcount);
-	unlock_page(hpage);
-	i_mmap_lock_write(mapping);
-	lock_page(hpage);
-	atomic_add_negative(-1, &hpage->_mapcount);
-
-	/* verify page is still mapped */
-	if (!page_mapped(hpage)) {
-		i_mmap_unlock_write(mapping);
-		return NULL;
-	}
-
-	/*
-	 * Get address space again and verify it is the same one
-	 * we locked.  If not, drop lock and retry.
-	 */
-	mapping2 = _get_hugetlb_page_mapping(hpage);
-	if (mapping2 != mapping) {
-		i_mmap_unlock_write(mapping);
-		mapping = mapping2;
-		goto retry;
-	}
-
-	return mapping;
+	return NULL;
 }
 
 pgoff_t __basepage_index(struct page *page)