On Mon, Mar 02, 2020 at 05:00:24PM +0800, lampahome wrote: > According to case insensitive since kernel 5.2, d_compare will > transform string into normalized form and then compare. > > But why do we need this normalization function? Could we just compare > by utf8 string? Have you read https://en.wikipedia.org/wiki/Unicode_equivalence ? We need to decide whether a user with a case-insensitive filesystem who looks up a file with the name U+00E5 (lower case "a" with ring) should find a file which is named U+00C5 (upper case "A" with ring) or U+212B (Angstrom sign). Then there's the question of whether e-acute is stored as U+00E9 or U+0065 followed by U+0301, and both of those will need to be found by a user search for U+00C9 or a user searching for U+0045 U+0301. So yes, normalisation needs to be done.
