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-rw-r--r--mm/hugetlb.c90
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)