f2fs: fix error handling in f2fs_end_enable_verity()

index 054ec852b5ea4..15ba36926fad7 100644
@@ -152,40 +152,73 @@ static int f2fs_end_enable_verity(struct file *filp, const void *desc,
 				  size_t desc_size, u64 merkle_tree_size)
 {
 	struct inode *inode = file_inode(filp);
+	struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
 	u64 desc_pos = f2fs_verity_metadata_pos(inode) + merkle_tree_size;
 	struct fsverity_descriptor_location dloc = {
 		.version = cpu_to_le32(F2FS_VERIFY_VER),
 		.size = cpu_to_le32(desc_size),
 		.pos = cpu_to_le64(desc_pos),
 	};
-	int err = 0;
+	int err = 0, err2 = 0;
 
-	if (desc != NULL) {
-		/* Succeeded; write the verity descriptor. */
-		err = pagecache_write(inode, desc, desc_size, desc_pos);
+	/*
+	 * If an error already occurred (which fs/verity/ signals by passing
+	 * desc == NULL), then only clean-up is needed.
+	 */
+	if (desc == NULL)
+		goto cleanup;
 
-		/* Write all pages before clearing FI_VERITY_IN_PROGRESS. */
-		if (!err)
-			err = filemap_write_and_wait(inode->i_mapping);
-	}
+	/* Append the verity descriptor. */
+	err = pagecache_write(inode, desc, desc_size, desc_pos);
+	if (err)
+		goto cleanup;
+
+	/*
+	 * Write all pages (both data and verity metadata).  Note that this must
+	 * happen before clearing FI_VERITY_IN_PROGRESS; otherwise pages beyond
+	 * i_size won't be written properly.  For crash consistency, this also
+	 * must happen before the verity inode flag gets persisted.
+	 */
+	err = filemap_write_and_wait(inode->i_mapping);
+	if (err)
+		goto cleanup;
+
+	/* Set the verity xattr. */
+	err = f2fs_setxattr(inode, F2FS_XATTR_INDEX_VERITY,
+			    F2FS_XATTR_NAME_VERITY, &dloc, sizeof(dloc),
+			    NULL, XATTR_CREATE);
+	if (err)
+		goto cleanup;
 
-	/* If we failed, truncate anything we wrote past i_size. */
-	if (desc == NULL || err)
-		f2fs_truncate(inode);
+	/* Finally, set the verity inode flag. */
+	file_set_verity(inode);
+	f2fs_set_inode_flags(inode);
+	f2fs_mark_inode_dirty_sync(inode, true);
 
 	clear_inode_flag(inode, FI_VERITY_IN_PROGRESS);
+	return 0;
 
-	if (desc != NULL && !err) {
-		err = f2fs_setxattr(inode, F2FS_XATTR_INDEX_VERITY,
-				    F2FS_XATTR_NAME_VERITY, &dloc, sizeof(dloc),
-				    NULL, XATTR_CREATE);
-		if (!err) {
-			file_set_verity(inode);
-			f2fs_set_inode_flags(inode);
-			f2fs_mark_inode_dirty_sync(inode, true);
-		}
+cleanup:
+	/*
+	 * Verity failed to be enabled, so clean up by truncating any verity
+	 * metadata that was written beyond i_size (both from cache and from
+	 * disk) and clearing FI_VERITY_IN_PROGRESS.
+	 *
+	 * Taking i_gc_rwsem[WRITE] is needed to stop f2fs garbage collection
+	 * from re-instantiating cached pages we are truncating (since unlike
+	 * normal file accesses, garbage collection isn't limited by i_size).
+	 */
+	down_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
+	truncate_inode_pages(inode->i_mapping, inode->i_size);
+	err2 = f2fs_truncate(inode);
+	if (err2) {
+		f2fs_err(sbi, "Truncating verity metadata failed (errno=%d)",
+			 err2);
+		set_sbi_flag(sbi, SBI_NEED_FSCK);
 	}
-	return err;
+	up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
+	clear_inode_flag(inode, FI_VERITY_IN_PROGRESS);
+	return err ?: err2;
 }
 
 static int f2fs_get_verity_descriptor(struct inode *inode, void *buf,