fs/ntfs3: Fix fiemap + fix shrink file size (to remove preallocated space)

Two problems:
1. ntfs3_setattr can't truncate preallocated space;
2. if allocated fragment "cross" valid size, then fragment splits into two parts:
- normal part;
- unwritten part (here we must return FIEMAP_EXTENT_LAST).
Before this commit we returned FIEMAP_EXTENT_LAST for whole fragment.
Fixes xfstest generic/092
Fixes: 4342306f ("fs/ntfs3: Add file operations and implementation")
Signed-off-by: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>

fs/ntfs3/file.c

@@ -761,7 +761,7 @@ int ntfs3_setattr(struct user_namespace *mnt_userns, struct dentry *dentry,
 		}
 		inode_dio_wait(inode);
 
-		if (attr->ia_size < oldsize)
+		if (attr->ia_size <= oldsize)
 			err = ntfs_truncate(inode, attr->ia_size);
 		else if (attr->ia_size > oldsize)
 			err = ntfs_extend(inode, attr->ia_size, 0, NULL);

fs/ntfs3/frecord.c

@@ -1964,10 +1964,8 @@ int ni_fiemap(struct ntfs_inode *ni, struct fiemap_extent_info *fieinfo,
 
 		vcn += clen;
 
-		if (vbo + bytes >= end) {
+		if (vbo + bytes >= end)
 			bytes = end - vbo;
-			flags |= FIEMAP_EXTENT_LAST;
-		}
 
 		if (vbo + bytes <= valid) {
 			;
@@ -1977,6 +1975,9 @@ int ni_fiemap(struct ntfs_inode *ni, struct fiemap_extent_info *fieinfo,
 			/* vbo < valid && valid < vbo + bytes */
 			u64 dlen = valid - vbo;
 
+			if (vbo + dlen >= end)
+				flags |= FIEMAP_EXTENT_LAST;
+
 			err = fiemap_fill_next_extent(fieinfo, vbo, lbo, dlen,
 						      flags);
 			if (err < 0)
@@ -1995,6 +1996,9 @@ int ni_fiemap(struct ntfs_inode *ni, struct fiemap_extent_info *fieinfo,
 			flags |= FIEMAP_EXTENT_UNWRITTEN;
 		}
 
+		if (vbo + bytes >= end)
+			flags |= FIEMAP_EXTENT_LAST;
+
 		err = fiemap_fill_next_extent(fieinfo, vbo, lbo, bytes, flags);
 		if (err < 0)
 			break;