On Fri 18-04-25 14:57:56, Mateusz Guzik wrote: > This reduces the slowdown in face of multiple callers issuing close on > what turns out to not be the last reference. > > Signed-off-by: Mateusz Guzik <mjguzik@xxxxxxxxx> > Reported-by: kernel test robot <oliver.sang@xxxxxxxxx> > Closes: https://lore.kernel.org/oe-lkp/202504171513.6d6f8a16-lkp@xxxxxxxxx Yeah, this looks good. Feel free to add: Reviewed-by: Jan Kara <jack@xxxxxxx> Honza > --- > > v2: > - fix a copy pasto with bad conditional > > fs/file.c | 2 +- > include/linux/file_ref.h | 19 ++++++------------- > 2 files changed, 7 insertions(+), 14 deletions(-) > > diff --git a/fs/file.c b/fs/file.c > index dc3f7e120e3e..3a3146664cf3 100644 > --- a/fs/file.c > +++ b/fs/file.c > @@ -26,7 +26,7 @@ > > #include "internal.h" > > -bool __file_ref_put_badval(file_ref_t *ref, unsigned long cnt) > +static noinline bool __file_ref_put_badval(file_ref_t *ref, unsigned long cnt) > { > /* > * If the reference count was already in the dead zone, then this > diff --git a/include/linux/file_ref.h b/include/linux/file_ref.h > index 7db62fbc0500..31551e4cb8f3 100644 > --- a/include/linux/file_ref.h > +++ b/include/linux/file_ref.h > @@ -61,7 +61,6 @@ static inline void file_ref_init(file_ref_t *ref, unsigned long cnt) > atomic_long_set(&ref->refcnt, cnt - 1); > } > > -bool __file_ref_put_badval(file_ref_t *ref, unsigned long cnt); > bool __file_ref_put(file_ref_t *ref, unsigned long cnt); > > /** > @@ -178,20 +177,14 @@ static __always_inline __must_check bool file_ref_put(file_ref_t *ref) > */ > static __always_inline __must_check bool file_ref_put_close(file_ref_t *ref) > { > - long old, new; > + long old; > > old = atomic_long_read(&ref->refcnt); > - do { > - if (unlikely(old < 0)) > - return __file_ref_put_badval(ref, old); > - > - if (old == FILE_REF_ONEREF) > - new = FILE_REF_DEAD; > - else > - new = old - 1; > - } while (!atomic_long_try_cmpxchg(&ref->refcnt, &old, new)); > - > - return new == FILE_REF_DEAD; > + if (likely(old == FILE_REF_ONEREF)) { > + if (likely(atomic_long_try_cmpxchg(&ref->refcnt, &old, FILE_REF_DEAD))) > + return true; > + } > + return file_ref_put(ref); > } > > /** > -- > 2.48.1 > -- Jan Kara <jack@xxxxxxxx> SUSE Labs, CR
