Re: [PATCH v6 1/3] exfat: add a Bloom filter for negative name lookups

[Namjae Jeon]

On Wed, Sep 23, 2026 at 9:33 PM Yang Wen <anmuxixixi@xxxxxxxxx> wrote:
>
> Negative name lookups scan a directory from the beginning. Repeating this
> scan before creating each file makes bulk creation approach O(N^2).
>
> Add a 64 KiB per-directory Bloom filter. Build it lazily after a directory
> reaches 1024 on-disk entries. A definite miss skips the directory scan,
> while a possible match follows the normal lookup path so hash collisions
> cannot affect correctness.
A fixed size of 64 KiB is excessive for a directory with 1024 dentries
(roughly 340 files). Conversely, for very large directories (1M+
files), the false-positive rate approaches nearly 100%. Because
deleted names are never removed, the structure only keeps filling up,
so shouldn’t the size be adjusted to the directory or regenerated on
saturation?

Thanks.