On 12/26/22 6:33 PM, Hou Tao wrote: > From: Hou Tao <houtao1@xxxxxxxxxx> > > fscache_create_volume_work() uses wake_up_bit() to wake up the processes > which are waiting for the completion of volume creation. According to > comments in wake_up_bit() and waitqueue_active(), an extra smp_mb() is > needed to guarantee the memory order between FSCACHE_VOLUME_CREATING > flag and waitqueue_active() before invoking wake_up_bit(). > > Considering clear_bit_unlock() before wake_up_bit() is an atomic > operation, use smp_mb__after_atomic() instead of smp_mb() to provide > such guarantee. > > Signed-off-by: Hou Tao <houtao1@xxxxxxxxxx> > --- > fs/fscache/volume.c | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/fs/fscache/volume.c b/fs/fscache/volume.c > index fc3dd3bc851d..734d17f404e7 100644 > --- a/fs/fscache/volume.c > +++ b/fs/fscache/volume.c > @@ -281,6 +281,11 @@ static void fscache_create_volume_work(struct work_struct *work) > fscache_access_acquire_volume_end); > > clear_bit_unlock(FSCACHE_VOLUME_CREATING, &volume->flags); > + /* > + * Paired with barrier in wait_on_bit(). Check wake_up_bit() and > + * waitqueue_active() for details. > + */ > + smp_mb__after_atomic(); > wake_up_bit(&volume->flags, FSCACHE_VOLUME_CREATING); > fscache_put_volume(volume, fscache_volume_put_create_work); > } LGTM. Actually I'm thinking if clear_and_wake_up_bit() could be used here. Ditto for patch 1. -- Thanks, Jingbo -- Linux-cachefs mailing list Linux-cachefs@xxxxxxxxxx https://listman.redhat.com/mailman/listinfo/linux-cachefs
