Am 23.03.21 um 12:46 schrieb Michal Hocko:
On Tue 23-03-21 12:28:20, Daniel Vetter wrote:
On Tue, Mar 23, 2021 at 08:38:33AM +0100, Michal Hocko wrote:
[...]
fs_reclaim_acquire is there to make sure lockdep understands that this
is a shrinker and that it checks all the dependencies for us like if
we'd be in real reclaim. There is some drop caches interfaces in proc
iirc, but those drop everything, and they don't have the fs_reclaim
annotations to teach lockdep about what we're doing.
... I really do not follow this. You shouldn't really care whether this
is a reclaim interface or not. Or maybe I just do not understand this...
We're heavily relying on lockdep and fs_reclaim to make sure we get it all
right. So any drop caches interface that isn't wrapped in fs_reclaim
context is kinda useless for testing. Plus ideally we want to only hit our
own paths, and not trash every other cache in the system. Speed matters in
CI.
But what is special about this path to hack around and make it pretend
it is part of the fs reclaim path?
That's just to teach lockdep that there is a dependency.
In other words we pretend in the debugfs file that it is part of the fs
reclaim path to check for the case when it really becomes part of the fs
reclaim path.
Regards,
Christian.
