Shyam Prasad N <nspmangalore@xxxxxxxxx> writes: > Hi Paulo, > > Thanks for your replies. > > On Mon, Jan 13, 2025 at 8:55 PM Paulo Alcantara <pc@xxxxxxxxxxxxx> wrote: >> >> Shyam Prasad N <nspmangalore@xxxxxxxxx> writes: >> >> > Ideally, negative dentries should allow a filename lookup to happen >> > entirely from the dentry cache if the lookup had happened once >> > already. But I noticed that the SMB client goes to the server every >> > time we do a stat of a file that does not exist. >> >> This is a network filesystem. If the last lookup ended up with a >> negative dentry in dcache, that doesn't mean the file won't exist the >> next time we look it up again. The file could have been created by a >> different client, so we need to query it on server. > > I agree. But we do have tools to trade performance for accuracy using > parameters like actimeo/acdirmax/acregmax. Do you mean using these parameters for negative dentries? These are used for caching file attributes of files and directories, which means they are all positive dentries. > So we can avoid going to the server each time if it's within some interval. > If the server gives us dir leases, we can be sure that the dentries > have not changed without us knowing. So we can definitely cache the > negative dentries till as long as we have the lease. Yes, that could be done with directory leases. Note that negative dentries are also cached when @lookupCacheEnabled is set.
