On Mon, Jul 17, 2017 at 3:39 PM, Waiman Long <longman@xxxxxxxxxx> wrote: > The number of positive dentries is limited by the number of files > in the filesystems. The number of negative dentries, however, > has no limit other than the total amount of memory available in > the system. So a rogue application that generates a lot of negative > dentries can potentially exhaust most of the memory available in the > system impacting performance on other running applications. > > To prevent this from happening, the dcache code is now updated to limit > the amount of the negative dentries in the LRU lists that can be kept > as a percentage of total available system memory. The default is 5% > and can be changed by specifying the "neg_dentry_pc=" kernel command > line option. > > Signed-off-by: Waiman Long <longman@xxxxxxxxxx> > --- [...] > @@ -603,7 +698,13 @@ static struct dentry *dentry_kill(struct dentry *dentry) > > if (!IS_ROOT(dentry)) { > parent = dentry->d_parent; > - if (unlikely(!spin_trylock(&parent->d_lock))) { > + /* > + * Force the killing of this negative dentry when > + * DCACHE_KILL_NEGATIVE flag is set. > + */ > + if (unlikely(dentry->d_flags & DCACHE_KILL_NEGATIVE)) { > + spin_lock(&parent->d_lock); This looks like d_lock ordering problem (should be parent first, child second). Why is this needed, anyway? > + } else if (unlikely(!spin_trylock(&parent->d_lock))) { > if (inode) > spin_unlock(&inode->i_lock); > goto failed; Thanks, Miklos -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html