On Mon, Aug 28, 2023 at 10:04 AM Yu Kuai <yukuai1@xxxxxxxxxxxxxxx> wrote: > > From: Yu Kuai <yukuai3@xxxxxxxxxx> > > Because reading 'suspend_lo' and 'suspend_hi' from md_handle_request() > is not protected, use READ_ONCE/WRITE_ONCE to prevent reading abnormal > value. Hi Kuai If we don't use READ_ONCE/WRITE_ONCE, What's the risk here? Could you explain in detail or give an example? Regards Xiao > > Signed-off-by: Yu Kuai <yukuai3@xxxxxxxxxx> > --- > drivers/md/md.c | 16 +++++++++------- > 1 file changed, 9 insertions(+), 7 deletions(-) > > diff --git a/drivers/md/md.c b/drivers/md/md.c > index 46badd13a687..9d8dff9d923c 100644 > --- a/drivers/md/md.c > +++ b/drivers/md/md.c > @@ -359,11 +359,11 @@ static bool is_suspended(struct mddev *mddev, struct bio *bio) > return true; > if (bio_data_dir(bio) != WRITE) > return false; > - if (mddev->suspend_lo >= mddev->suspend_hi) > + if (READ_ONCE(mddev->suspend_lo) >= READ_ONCE(mddev->suspend_hi)) > return false; > - if (bio->bi_iter.bi_sector >= mddev->suspend_hi) > + if (bio->bi_iter.bi_sector >= READ_ONCE(mddev->suspend_hi)) > return false; > - if (bio_end_sector(bio) < mddev->suspend_lo) > + if (bio_end_sector(bio) < READ_ONCE(mddev->suspend_lo)) > return false; > return true; > } > @@ -5171,7 +5171,8 @@ __ATTR(sync_max, S_IRUGO|S_IWUSR, max_sync_show, max_sync_store); > static ssize_t > suspend_lo_show(struct mddev *mddev, char *page) > { > - return sprintf(page, "%llu\n", (unsigned long long)mddev->suspend_lo); > + return sprintf(page, "%llu\n", > + (unsigned long long)READ_ONCE(mddev->suspend_lo)); > } > > static ssize_t > @@ -5191,7 +5192,7 @@ suspend_lo_store(struct mddev *mddev, const char *buf, size_t len) > return err; > > mddev_suspend(mddev); > - mddev->suspend_lo = new; > + WRITE_ONCE(mddev->suspend_lo, new); > mddev_resume(mddev); > > mddev_unlock(mddev); > @@ -5203,7 +5204,8 @@ __ATTR(suspend_lo, S_IRUGO|S_IWUSR, suspend_lo_show, suspend_lo_store); > static ssize_t > suspend_hi_show(struct mddev *mddev, char *page) > { > - return sprintf(page, "%llu\n", (unsigned long long)mddev->suspend_hi); > + return sprintf(page, "%llu\n", > + (unsigned long long)READ_ONCE(mddev->suspend_hi)); > } > > static ssize_t > @@ -5223,7 +5225,7 @@ suspend_hi_store(struct mddev *mddev, const char *buf, size_t len) > return err; > > mddev_suspend(mddev); > - mddev->suspend_hi = new; > + WRITE_ONCE(mddev->suspend_hi, new); > mddev_resume(mddev); > > mddev_unlock(mddev); > -- > 2.39.2 > -- dm-devel mailing list dm-devel@xxxxxxxxxx https://listman.redhat.com/mailman/listinfo/dm-devel