3.16.66-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Ilya Dryomov <idryomov@xxxxxxxxx> commit 85f5a4d666fd9be73856ed16bb36c5af5b406b29 upstream. There is a window between when RBD_DEV_FLAG_REMOVING is set and when the device is removed from rbd_dev_list. During this window, we set "already" and return 0. Returning 0 from write(2) can confuse userspace tools because 0 indicates that nothing was written. In particular, "rbd unmap" will retry the write multiple times a second: 10:28:05.463299 write(4, "0", 1) = 0 10:28:05.463509 write(4, "0", 1) = 0 10:28:05.463720 write(4, "0", 1) = 0 10:28:05.463942 write(4, "0", 1) = 0 10:28:05.464155 write(4, "0", 1) = 0 Signed-off-by: Ilya Dryomov <idryomov@xxxxxxxxx> Tested-by: Dongsheng Yang <dongsheng.yang@xxxxxxxxxxxx> [bwh: Backported to 3.16: adjust context] Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx> --- drivers/block/rbd.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-) --- a/drivers/block/rbd.c +++ b/drivers/block/rbd.c @@ -5422,7 +5422,6 @@ static ssize_t do_rbd_remove(struct bus_ struct list_head *tmp; int dev_id; unsigned long ul; - bool already = false; int ret; ret = kstrtoul(buf, 10, &ul); @@ -5447,13 +5446,13 @@ static ssize_t do_rbd_remove(struct bus_ spin_lock_irq(&rbd_dev->lock); if (rbd_dev->open_count) ret = -EBUSY; - else - already = test_and_set_bit(RBD_DEV_FLAG_REMOVING, - &rbd_dev->flags); + else if (test_and_set_bit(RBD_DEV_FLAG_REMOVING, + &rbd_dev->flags)) + ret = -EINPROGRESS; spin_unlock_irq(&rbd_dev->lock); } spin_unlock(&rbd_dev_list_lock); - if (ret < 0 || already) + if (ret) return ret; rbd_dev_header_unwatch_sync(rbd_dev);
