On 10/7/21 2:25 PM, Song Liu wrote:
On Mon, Oct 4, 2021 at 8:40 AM Guoqing Jiang <guoqing.jiang@xxxxxxxxx> wrote:We shouldn't set it since write behind IO should only happen to write mostly device. Signed-off-by: Guoqing Jiang <guoqing.jiang@xxxxxxxxx> --- drivers/md/md-bitmap.c | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) diff --git a/drivers/md/md-bitmap.c b/drivers/md/md-bitmap.c index e29c6298ef5c..0346281b1555 100644 --- a/drivers/md/md-bitmap.c +++ b/drivers/md/md-bitmap.c @@ -2469,11 +2469,28 @@ backlog_store(struct mddev *mddev, const char *buf, size_t len) { unsigned long backlog; unsigned long old_mwb = mddev->bitmap_info.max_write_behind; + struct md_rdev *rdev; + bool has_write_mostly = false; int rv = kstrtoul(buf, 10, &backlog); if (rv) return rv; if (backlog > COUNTER_MAX) return -EINVAL; + + /* + * Without write mostly device, it doesn't make sense to set + * backlog for max_write_behind. + */ + rdev_for_each(rdev, mddev) + if (test_bit(WriteMostly, &rdev->flags)) { + has_write_mostly = true; + break; + } + if (!has_write_mostly) { + pr_warn_ratelimited("md: No write mostly device available\n");Most of these _store functions do not print warnings for invalid changes. So I am not sure whether we want to add this one.
I think it is better to makes users know the reason of invalidation.
If we do want it, we should make it clear, as "md: No write mostly device available. Cannot set backlog\n". We may also add the device name there.
Sure, I will make it clearer. Thanks, Guoqing
