On 4/6/17 11:26 AM, Theodore Ts'o wrote: > On Wed, Apr 05, 2017 at 10:35:26AM +0800, Eryu Guan wrote: >> >> Test fails with ext3/2 when driving with ext4 driver, fiemap changed >> after umount/mount cycle, then changed back to original result after >> sleeping some time. An ext4 bug? (cc'ed linux-ext4 list.) > > I haven't had time to look at this, but I'm not sure this test is a > reasonable one on the face of it. > > A file system may choose to optimize a file's extent tree for whatever > reason it wants, whenever it wants, including on an unmount --- and > that would not be an invalid thing to do. So to have an xfstests that > causes a test failure if a file system were to, say, do some cleanup > at mount or unmount time, or when the file is next opened, to merge > adjacent extents together (and hence change what is returned by > FIEMAP) might be strange, or even weird --- but is this any of user > space's business? Or anything we want to enforce as wrong wrong wrong > by xfstests? I had the same question. If the exact behavior isn't defined anywhere, I don't know what we can be testing, TBH. -Eric > - Ted
