Merge branch 'akpm' (patches from Andrew)

Merge fixes from Andrew Morton:
 "4 fixes"

* emailed patches from Andrew Morton <akpm@linux-foundation.org>:
  mm: thp: calculate the mapcount correctly for THP pages during WP faults
  ksm: fix conflict between mmput and scan_get_next_rmap_item
  ocfs2: fix posix_acl_create deadlock
  ocfs2: revert using ocfs2_acl_chmod to avoid inode cluster lock hang

13 files changed, 209 insertions, 81 deletions

diff --git a/fs/ocfs2/acl.c b/fs/ocfs2/acl.c
index 0cdf497c91ef..2162434728c0 100644
--- a/fs/ocfs2/acl.c
+++ b/fs/ocfs2/acl.c
@@ -322,3 +322,90 @@ struct posix_acl *ocfs2_iop_get_acl(struct inode *inode, int type)
 	brelse(di_bh);
 	return acl;
 }
+
+int ocfs2_acl_chmod(struct inode *inode, struct buffer_head *bh)
+{
+	struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
+	struct posix_acl *acl;
+	int ret;
+
+	if (S_ISLNK(inode->i_mode))
+		return -EOPNOTSUPP;
+
+	if (!(osb->s_mount_opt & OCFS2_MOUNT_POSIX_ACL))
+		return 0;
+
+	acl = ocfs2_get_acl_nolock(inode, ACL_TYPE_ACCESS, bh);
+	if (IS_ERR(acl) || !acl)
+		return PTR_ERR(acl);
+	ret = __posix_acl_chmod(&acl, GFP_KERNEL, inode->i_mode);
+	if (ret)
+		return ret;
+	ret = ocfs2_set_acl(NULL, inode, NULL, ACL_TYPE_ACCESS,
+			    acl, NULL, NULL);
+	posix_acl_release(acl);
+	return ret;
+}
+
+/*
+ * Initialize the ACLs of a new inode. If parent directory has default ACL,
+ * then clone to new inode. Called from ocfs2_mknod.
+ */
+int ocfs2_init_acl(handle_t *handle,
+		   struct inode *inode,
+		   struct inode *dir,
+		   struct buffer_head *di_bh,
+		   struct buffer_head *dir_bh,
+		   struct ocfs2_alloc_context *meta_ac,
+		   struct ocfs2_alloc_context *data_ac)
+{
+	struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
+	struct posix_acl *acl = NULL;
+	int ret = 0, ret2;
+	umode_t mode;
+
+	if (!S_ISLNK(inode->i_mode)) {
+		if (osb->s_mount_opt & OCFS2_MOUNT_POSIX_ACL) {
+			acl = ocfs2_get_acl_nolock(dir, ACL_TYPE_DEFAULT,
+						   dir_bh);
+			if (IS_ERR(acl))
+				return PTR_ERR(acl);
+		}
+		if (!acl) {
+			mode = inode->i_mode & ~current_umask();
+			ret = ocfs2_acl_set_mode(inode, di_bh, handle, mode);
+			if (ret) {
+				mlog_errno(ret);
+				goto cleanup;
+			}
+		}
+	}
+	if ((osb->s_mount_opt & OCFS2_MOUNT_POSIX_ACL) && acl) {
+		if (S_ISDIR(inode->i_mode)) {
+			ret = ocfs2_set_acl(handle, inode, di_bh,
+					    ACL_TYPE_DEFAULT, acl,
+					    meta_ac, data_ac);
+			if (ret)
+				goto cleanup;
+		}
+		mode = inode->i_mode;
+		ret = __posix_acl_create(&acl, GFP_NOFS, &mode);
+		if (ret < 0)
+			return ret;
+
+		ret2 = ocfs2_acl_set_mode(inode, di_bh, handle, mode);
+		if (ret2) {
+			mlog_errno(ret2);
+			ret = ret2;
+			goto cleanup;
+		}
+		if (ret > 0) {
+			ret = ocfs2_set_acl(handle, inode,
+					    di_bh, ACL_TYPE_ACCESS,
+					    acl, meta_ac, data_ac);
+		}
+	}
+cleanup:
+	posix_acl_release(acl);
+	return ret;
+}
diff --git a/fs/ocfs2/acl.h b/fs/ocfs2/acl.h
index 3fce68d08625..2783a75b3999 100644
--- a/fs/ocfs2/acl.h
+++ b/fs/ocfs2/acl.h
@@ -35,5 +35,10 @@ int ocfs2_set_acl(handle_t *handle,
 			 struct posix_acl *acl,
 			 struct ocfs2_alloc_context *meta_ac,
 			 struct ocfs2_alloc_context *data_ac);
+extern int ocfs2_acl_chmod(struct inode *, struct buffer_head *);
+extern int ocfs2_init_acl(handle_t *, struct inode *, struct inode *,
+			  struct buffer_head *, struct buffer_head *,
+			  struct ocfs2_alloc_context *,
+			  struct ocfs2_alloc_context *);
 
 #endif /* OCFS2_ACL_H */
diff --git a/fs/ocfs2/file.c b/fs/ocfs2/file.c
index 5308841756be..59cce53c91d8 100644
--- a/fs/ocfs2/file.c
+++ b/fs/ocfs2/file.c
@@ -1268,20 +1268,20 @@ bail_unlock_rw:
 	if (size_change)
 		ocfs2_rw_unlock(inode, 1);
 bail:
-	brelse(bh);
 
 	/* Release quota pointers in case we acquired them */
 	for (qtype = 0; qtype < OCFS2_MAXQUOTAS; qtype++)
 		dqput(transfer_to[qtype]);
 
 	if (!status && attr->ia_valid & ATTR_MODE) {
-		status = posix_acl_chmod(inode, inode->i_mode);
+		status = ocfs2_acl_chmod(inode, bh);
 		if (status < 0)
 			mlog_errno(status);
 	}
 	if (inode_locked)
 		ocfs2_inode_unlock(inode, 1);
 
+	brelse(bh);
 	return status;
 }
 
diff --git a/fs/ocfs2/namei.c b/fs/ocfs2/namei.c
index 6b3e87189a64..a8f1225e6d9b 100644
--- a/fs/ocfs2/namei.c
+++ b/fs/ocfs2/namei.c
@@ -259,7 +259,6 @@ static int ocfs2_mknod(struct inode *dir,
 	struct ocfs2_dir_lookup_result lookup = { NULL, };
 	sigset_t oldset;
 	int did_block_signals = 0;
-	struct posix_acl *default_acl = NULL, *acl = NULL;
 	struct ocfs2_dentry_lock *dl = NULL;
 
 	trace_ocfs2_mknod(dir, dentry, dentry->d_name.len, dentry->d_name.name,
@@ -367,12 +366,6 @@ static int ocfs2_mknod(struct inode *dir,
 		goto leave;
 	}
 
-	status = posix_acl_create(dir, &inode->i_mode, &default_acl, &acl);
-	if (status) {
-		mlog_errno(status);
-		goto leave;
-	}
-
 	handle = ocfs2_start_trans(osb, ocfs2_mknod_credits(osb->sb,
 							    S_ISDIR(mode),
 							    xattr_credits));
@@ -421,16 +414,8 @@ static int ocfs2_mknod(struct inode *dir,
 		inc_nlink(dir);
 	}
 
-	if (default_acl) {
-		status = ocfs2_set_acl(handle, inode, new_fe_bh,
-				       ACL_TYPE_DEFAULT, default_acl,
-				       meta_ac, data_ac);
-	}
-	if (!status && acl) {
-		status = ocfs2_set_acl(handle, inode, new_fe_bh,
-				       ACL_TYPE_ACCESS, acl,
-				       meta_ac, data_ac);
-	}
+	status = ocfs2_init_acl(handle, inode, dir, new_fe_bh, parent_fe_bh,
+			 meta_ac, data_ac);
 
 	if (status < 0) {
 		mlog_errno(status);
@@ -472,10 +457,6 @@ static int ocfs2_mknod(struct inode *dir,
 	d_instantiate(dentry, inode);
 	status = 0;
 leave:
-	if (default_acl)
-		posix_acl_release(default_acl);
-	if (acl)
-		posix_acl_release(acl);
 	if (status < 0 && did_quota_inode)
 		dquot_free_inode(inode);
 	if (handle)
diff --git a/fs/ocfs2/refcounttree.c b/fs/ocfs2/refcounttree.c
index 744d5d90c363..92bbe93bfe10 100644
--- a/fs/ocfs2/refcounttree.c
+++ b/fs/ocfs2/refcounttree.c
@@ -4248,20 +4248,12 @@ static int ocfs2_reflink(struct dentry *old_dentry, struct inode *dir,
 	struct inode *inode = d_inode(old_dentry);
 	struct buffer_head *old_bh = NULL;
 	struct inode *new_orphan_inode = NULL;
-	struct posix_acl *default_acl, *acl;
-	umode_t mode;
 
 	if (!ocfs2_refcount_tree(OCFS2_SB(inode->i_sb)))
 		return -EOPNOTSUPP;
 
-	mode = inode->i_mode;
-	error = posix_acl_create(dir, &mode, &default_acl, &acl);
-	if (error) {
-		mlog_errno(error);
-		return error;
-	}
 
-	error = ocfs2_create_inode_in_orphan(dir, mode,
+	error = ocfs2_create_inode_in_orphan(dir, inode->i_mode,
 					     &new_orphan_inode);
 	if (error) {
 		mlog_errno(error);
@@ -4300,16 +4292,11 @@ static int ocfs2_reflink(struct dentry *old_dentry, struct inode *dir,
 	/* If the security isn't preserved, we need to re-initialize them. */
 	if (!preserve) {
 		error = ocfs2_init_security_and_acl(dir, new_orphan_inode,
-						    &new_dentry->d_name,
-						    default_acl, acl);
+						    &new_dentry->d_name);
 		if (error)
 			mlog_errno(error);
 	}
 out:
-	if (default_acl)
-		posix_acl_release(default_acl);
-	if (acl)
-		posix_acl_release(acl);
 	if (!error) {
 		error = ocfs2_mv_orphaned_inode_to_new(dir, new_orphan_inode,
 						       new_dentry);
diff --git a/fs/ocfs2/xattr.c b/fs/ocfs2/xattr.c
index 7d3d979f57d9..f19b7381a998 100644
--- a/fs/ocfs2/xattr.c
+++ b/fs/ocfs2/xattr.c
@@ -7216,12 +7216,10 @@ out:
  */
 int ocfs2_init_security_and_acl(struct inode *dir,
 				struct inode *inode,
-				const struct qstr *qstr,
-				struct posix_acl *default_acl,
-				struct posix_acl *acl)
+				const struct qstr *qstr)
 {
-	struct buffer_head *dir_bh = NULL;
 	int ret = 0;
+	struct buffer_head *dir_bh = NULL;
 
 	ret = ocfs2_init_security_get(inode, dir, qstr, NULL);
 	if (ret) {
@@ -7234,11 +7232,9 @@ int ocfs2_init_security_and_acl(struct inode *dir,
 		mlog_errno(ret);
 		goto leave;
 	}
-
-	if (!ret && default_acl)
-		ret = ocfs2_iop_set_acl(inode, default_acl, ACL_TYPE_DEFAULT);
-	if (!ret && acl)
-		ret = ocfs2_iop_set_acl(inode, acl, ACL_TYPE_ACCESS);
+	ret = ocfs2_init_acl(NULL, inode, dir, NULL, dir_bh, NULL, NULL);
+	if (ret)
+		mlog_errno(ret);
 
 	ocfs2_inode_unlock(dir, 0);
 	brelse(dir_bh);
diff --git a/fs/ocfs2/xattr.h b/fs/ocfs2/xattr.h
index f10d5b93c366..1633cc15ea1f 100644
--- a/fs/ocfs2/xattr.h
+++ b/fs/ocfs2/xattr.h
@@ -94,7 +94,5 @@ int ocfs2_reflink_xattrs(struct inode *old_inode,
 			 bool preserve_security);
 int ocfs2_init_security_and_acl(struct inode *dir,
 				struct inode *inode,
-				const struct qstr *qstr,
-				struct posix_acl *default_acl,
-				struct posix_acl *acl);
+				const struct qstr *qstr);
 #endif /* OCFS2_XATTR_H */
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 864d7221de84..8f468e0d2534 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -500,11 +500,20 @@ static inline int page_mapcount(struct page *page)
 
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 int total_mapcount(struct page *page);
+int page_trans_huge_mapcount(struct page *page, int *total_mapcount);
 #else
 static inline int total_mapcount(struct page *page)
 {
 	return page_mapcount(page);
 }
+static inline int page_trans_huge_mapcount(struct page *page,
+					   int *total_mapcount)
+{
+	int mapcount = page_mapcount(page);
+	if (total_mapcount)
+		*total_mapcount = mapcount;
+	return mapcount;
+}
 #endif
 
 static inline struct page *virt_to_head_page(const void *x)
diff --git a/include/linux/swap.h b/include/linux/swap.h
index 0a4cd4703f40..ad220359f1b0 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -418,7 +418,7 @@ extern sector_t swapdev_block(int, pgoff_t);
 extern int page_swapcount(struct page *);
 extern int swp_swapcount(swp_entry_t entry);
 extern struct swap_info_struct *page_swap_info(struct page *);
-extern int reuse_swap_page(struct page *);
+extern bool reuse_swap_page(struct page *, int *);
 extern int try_to_free_swap(struct page *);
 struct backing_dev_info;
 
@@ -513,8 +513,8 @@ static inline int swp_swapcount(swp_entry_t entry)
 	return 0;
 }
 
-#define reuse_swap_page(page) \
-	(!PageTransCompound(page) && page_mapcount(page) == 1)
+#define reuse_swap_page(page, total_mapcount) \
+	(page_trans_huge_mapcount(page, total_mapcount) == 1)
 
 static inline int try_to_free_swap(struct page *page)
 {
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index f7daa7de8f48..b49ee126d4d1 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1298,15 +1298,9 @@ int do_huge_pmd_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
 	VM_BUG_ON_PAGE(!PageCompound(page) || !PageHead(page), page);
 	/*
 	 * We can only reuse the page if nobody else maps the huge page or it's
-	 * part. We can do it by checking page_mapcount() on each sub-page, but
-	 * it's expensive.
-	 * The cheaper way is to check page_count() to be equal 1: every
-	 * mapcount takes page reference reference, so this way we can
-	 * guarantee, that the PMD is the only mapping.
-	 * This can give false negative if somebody pinned the page, but that's
-	 * fine.
+	 * part.
 	 */
-	if (page_mapcount(page) == 1 && page_count(page) == 1) {
+	if (page_trans_huge_mapcount(page, NULL) == 1) {
 		pmd_t entry;
 		entry = pmd_mkyoung(orig_pmd);
 		entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
@@ -2079,7 +2073,8 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
 		if (pte_write(pteval)) {
 			writable = true;
 		} else {
-			if (PageSwapCache(page) && !reuse_swap_page(page)) {
+			if (PageSwapCache(page) &&
+			    !reuse_swap_page(page, NULL)) {
 				unlock_page(page);
 				result = SCAN_SWAP_CACHE_PAGE;
 				goto out;
@@ -3223,6 +3218,64 @@ int total_mapcount(struct page *page)
 }
 
 /*
+ * This calculates accurately how many mappings a transparent hugepage
+ * has (unlike page_mapcount() which isn't fully accurate). This full
+ * accuracy is primarily needed to know if copy-on-write faults can
+ * reuse the page and change the mapping to read-write instead of
+ * copying them. At the same time this returns the total_mapcount too.
+ *
+ * The function returns the highest mapcount any one of the subpages
+ * has. If the return value is one, even if different processes are
+ * mapping different subpages of the transparent hugepage, they can
+ * all reuse it, because each process is reusing a different subpage.
+ *
+ * The total_mapcount is instead counting all virtual mappings of the
+ * subpages. If the total_mapcount is equal to "one", it tells the
+ * caller all mappings belong to the same "mm" and in turn the
+ * anon_vma of the transparent hugepage can become the vma->anon_vma
+ * local one as no other process may be mapping any of the subpages.
+ *
+ * It would be more accurate to replace page_mapcount() with
+ * page_trans_huge_mapcount(), however we only use
+ * page_trans_huge_mapcount() in the copy-on-write faults where we
+ * need full accuracy to avoid breaking page pinning, because
+ * page_trans_huge_mapcount() is slower than page_mapcount().
+ */
+int page_trans_huge_mapcount(struct page *page, int *total_mapcount)
+{
+	int i, ret, _total_mapcount, mapcount;
+
+	/* hugetlbfs shouldn't call it */
+	VM_BUG_ON_PAGE(PageHuge(page), page);
+
+	if (likely(!PageTransCompound(page))) {
+		mapcount = atomic_read(&page->_mapcount) + 1;
+		if (total_mapcount)
+			*total_mapcount = mapcount;
+		return mapcount;
+	}
+
+	page = compound_head(page);
+
+	_total_mapcount = ret = 0;
+	for (i = 0; i < HPAGE_PMD_NR; i++) {
+		mapcount = atomic_read(&page[i]._mapcount) + 1;
+		ret = max(ret, mapcount);
+		_total_mapcount += mapcount;
+	}
+	if (PageDoubleMap(page)) {
+		ret -= 1;
+		_total_mapcount -= HPAGE_PMD_NR;
+	}
+	mapcount = compound_mapcount(page);
+	ret += mapcount;
+	_total_mapcount += mapcount;
+	if (total_mapcount)
+		*total_mapcount = _total_mapcount;
+	return ret;
+}
+
+/*
  * This function splits huge page into normal pages. @page can point to any
  * subpage of huge page to split. Split doesn't change the position of @page.
  *
diff --git a/mm/ksm.c b/mm/ksm.c
index b99e828172f6..4786b4150f62 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -783,6 +783,7 @@ static int unmerge_and_remove_all_rmap_items(void)
 		}
 
 		remove_trailing_rmap_items(mm_slot, &mm_slot->rmap_list);
+		up_read(&mm->mmap_sem);
 
 		spin_lock(&ksm_mmlist_lock);
 		ksm_scan.mm_slot = list_entry(mm_slot->mm_list.next,
@@ -794,12 +795,9 @@ static int unmerge_and_remove_all_rmap_items(void)
 
 			free_mm_slot(mm_slot);
 			clear_bit(MMF_VM_MERGEABLE, &mm->flags);
-			up_read(&mm->mmap_sem);
 			mmdrop(mm);
-		} else {
+		} else
 			spin_unlock(&ksm_mmlist_lock);
-			up_read(&mm->mmap_sem);
-		}
 	}
 
 	/* Clean up stable nodes, but don't worry if some are still busy */
@@ -1663,8 +1661,15 @@ next_mm:
 		up_read(&mm->mmap_sem);
 		mmdrop(mm);
 	} else {
-		spin_unlock(&ksm_mmlist_lock);
 		up_read(&mm->mmap_sem);
+		/*
+		 * up_read(&mm->mmap_sem) first because after
+		 * spin_unlock(&ksm_mmlist_lock) run, the "mm" may
+		 * already have been freed under us by __ksm_exit()
+		 * because the "mm_slot" is still hashed and
+		 * ksm_scan.mm_slot doesn't point to it anymore.
+		 */
+		spin_unlock(&ksm_mmlist_lock);
 	}
 
 	/* Repeat until we've completed scanning the whole list */
diff --git a/mm/memory.c b/mm/memory.c
index 52c218e2b724..07493e34ab7e 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2373,6 +2373,7 @@ static int do_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
 	 * not dirty accountable.
 	 */
 	if (PageAnon(old_page) && !PageKsm(old_page)) {
+		int total_mapcount;
 		if (!trylock_page(old_page)) {
 			get_page(old_page);
 			pte_unmap_unlock(page_table, ptl);
@@ -2387,13 +2388,18 @@ static int do_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
 			}
 			put_page(old_page);
 		}
-		if (reuse_swap_page(old_page)) {
-			/*
-			 * The page is all ours.  Move it to our anon_vma so
-			 * the rmap code will not search our parent or siblings.
-			 * Protected against the rmap code by the page lock.
-			 */
-			page_move_anon_rmap(old_page, vma, address);
+		if (reuse_swap_page(old_page, &total_mapcount)) {
+			if (total_mapcount == 1) {
+				/*
+				 * The page is all ours. Move it to
+				 * our anon_vma so the rmap code will
+				 * not search our parent or siblings.
+				 * Protected against the rmap code by
+				 * the page lock.
+				 */
+				page_move_anon_rmap(compound_head(old_page),
+						    vma, address);
+			}
 			unlock_page(old_page);
 			return wp_page_reuse(mm, vma, address, page_table, ptl,
 					     orig_pte, old_page, 0, 0);
@@ -2617,7 +2623,7 @@ static int do_swap_page(struct mm_struct *mm, struct vm_area_struct *vma,
 	inc_mm_counter_fast(mm, MM_ANONPAGES);
 	dec_mm_counter_fast(mm, MM_SWAPENTS);
 	pte = mk_pte(page, vma->vm_page_prot);
-	if ((flags & FAULT_FLAG_WRITE) && reuse_swap_page(page)) {
+	if ((flags & FAULT_FLAG_WRITE) && reuse_swap_page(page, NULL)) {
 		pte = maybe_mkwrite(pte_mkdirty(pte), vma);
 		flags &= ~FAULT_FLAG_WRITE;
 		ret |= VM_FAULT_WRITE;
diff --git a/mm/swapfile.c b/mm/swapfile.c
index 83874eced5bf..031713ab40ce 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -922,18 +922,19 @@ out:
  * to it.  And as a side-effect, free up its swap: because the old content
  * on disk will never be read, and seeking back there to write new content
  * later would only waste time away from clustering.
+ *
+ * NOTE: total_mapcount should not be relied upon by the caller if
+ * reuse_swap_page() returns false, but it may be always overwritten
+ * (see the other implementation for CONFIG_SWAP=n).
  */
-int reuse_swap_page(struct page *page)
+bool reuse_swap_page(struct page *page, int *total_mapcount)
 {
 	int count;
 
 	VM_BUG_ON_PAGE(!PageLocked(page), page);
 	if (unlikely(PageKsm(page)))
-		return 0;
-	/* The page is part of THP and cannot be reused */
-	if (PageTransCompound(page))
-		return 0;
-	count = page_mapcount(page);
+		return false;
+	count = page_trans_huge_mapcount(page, total_mapcount);
 	if (count <= 1 && PageSwapCache(page)) {
 		count += page_swapcount(page);
 		if (count == 1 && !PageWriteback(page)) {