[PATCH 02/18] xstat: Add a pair of system calls to make extended file stats available [ver #6]

[David Howells]

utz lehmann <lkml123 at s2y4n2c.de> wrote:

> How does this works right with noatime or relatime (which is default)?

Don't do that then.

> We had used FS-Cache with a few 10000s files cached. Doesn't it mean
> that the cleanup has to stat them all?

Yes.

> Why didn't cachefilesd managed the cache index in a separate database
> like other caches?

Because using atime is much simpler since the filesystem updates it
automatically.  If you have a separate database then you have redundant
information and you need to maintain metadata integrity which has a cost, both
in terms of disk usage and performance.  I'm working on it, but you don't get
it for free.

David