Hi, On 1/12/2023 12:34 PM, Jingbo Xu wrote: > > On 12/26/22 6:33 PM, Hou Tao wrote: >> From: Hou Tao <hout...@huawei.com> >> >> 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 <hout...@huawei.com> >> --- >> 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. Good idea. Just find the presence of clear_and_wake_up_bit(). Will do in v3 for both patch 1 & patch 2. >
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