Re: [RFC/PATCH 8/8] read-cache: unlink old sharedindex files

On Mon, Jul 11, 2016 at 8:27 PM, Duy Nguyen [off-list ref] wrote:

On Mon, Jul 11, 2016 at 7:22 PM, Christian Couder
[off-list ref] wrote:

quoted

Everytime split index is turned on, it creates a "sharedindex.XXXX"
file in the git directory. This makes sure that old sharedindex
files are removed after a new one has been created.

Hmm it's one-way link, we don't know how many index files use this
shared index file, how can you be sure nobody else will need it? I'm
thinking about temporary indexes. If a temp index is created, saved on
disk, and use delete the shared index file, the real, main index may
become useless. Temp index will most likely replace the main index
(git commit) but if a failure happens, we can't fall back.

Isn't there a way to scan all the current indexes (temp or not) to see
which shared indexes they need?

A safer approach is "touch" the shared index every time a linked index
is used, then we can delete shared indexes with old mtime, older than
a grace period, in git-prune (or here).

Maybe old linked indexes could be converted after some time to use a
newer shared index, so that we can get rid of the old shared indexes.
That seems safer than just deleting old linked indexes.

Thanks for your review,
Christian.