On Fri, 28 Oct 2022, Jeff Layton wrote: > Currently, nfsd_files live on the LRU once they are added until they are > unhashed. There's no need to keep ones that are actively in use there. Is that true? nfsd_file_do_acquire() calls nfsd_file_lru_remove() Isn't that enough to keep the file off the lru while it is active? Thanks, NeilBrown > > Before incrementing the refcount, do a lockless check for nf_lru being > empty. If it's not then attempt to remove the entry from the LRU. If > that's successful, claim the LRU reference and return it. If the removal > fails (or if the list_head was empty), then just increment the counter > as we normally would. > > Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx> > --- > fs/nfsd/filecache.c | 23 ++++++++++++++++++++--- > 1 file changed, 20 insertions(+), 3 deletions(-) > > diff --git a/fs/nfsd/filecache.c b/fs/nfsd/filecache.c > index e63534f4b9f8..d2bbded805d4 100644 > --- a/fs/nfsd/filecache.c > +++ b/fs/nfsd/filecache.c > @@ -420,14 +420,31 @@ nfsd_file_unhash(struct nfsd_file *nf) > return false; > } > > -struct nfsd_file * > -nfsd_file_get(struct nfsd_file *nf) > +static struct nfsd_file * > +__nfsd_file_get(struct nfsd_file *nf) > { > if (likely(refcount_inc_not_zero(&nf->nf_ref))) > return nf; > return NULL; > } > > +struct nfsd_file * > +nfsd_file_get(struct nfsd_file *nf) > +{ > + /* > + * Do a lockless list_empty check first, before attempting to > + * remove it, so we can avoid the spinlock when it's not on the > + * list. > + * > + * If we successfully remove it from the LRU, then we can just > + * claim the LRU reference and return it. Otherwise, we need to > + * bump the counter the old-fashioned way. > + */ > + if (!list_empty(&nf->nf_lru) && nfsd_file_lru_remove(nf)) > + return nf; > + return __nfsd_file_get(nf); > +} > + > /** > * nfsd_file_unhash_and_queue - unhash a file and queue it to the dispose list > * @nf: nfsd_file to be unhashed and queued > @@ -449,7 +466,7 @@ nfsd_file_unhash_and_queue(struct nfsd_file *nf, struct list_head *dispose) > * to take a reference. If that fails, just ignore > * the file altogether. > */ > - if (!nfsd_file_lru_remove(nf) && !nfsd_file_get(nf)) > + if (!nfsd_file_lru_remove(nf) && !__nfsd_file_get(nf)) > return false; > list_add(&nf->nf_lru, dispose); > return true; > -- > 2.37.3 > >