From 6434f404b43afa0cfe54fec009760510431ca103 Mon Sep 17 00:00:00 2001 From: Lars Ellenberg Date: Wed, 25 Feb 2015 19:37:28 +0100 Subject: [PATCH] drbd: fix refcount error during detach of an already failed disk A D_FAILED disk transitions as quickly as possible to D_DISKLESS. But in the "unresponsive local disk" case, there remains a time window where a administrative detach command could find the disk already failed, but some internal meta data IO against the unresponsive local disk still pending. In that case, drbd_md_get_buffer() will return NULL. Don't unconditionally call drbd_md_put_buffer(), or it will cause refcount imbalance, and prevent any further re-attach on this volume (until it is deleted and re-created). Signed-off-by: Philipp Reisner Signed-off-by: Lars Ellenberg Signed-off-by: Jens Axboe --- drivers/block/drbd/drbd_nl.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) diff --git a/drivers/block/drbd/drbd_nl.c b/drivers/block/drbd/drbd_nl.c index 331b378b7d0b..79dc3d4f5aee 100644 --- a/drivers/block/drbd/drbd_nl.c +++ b/drivers/block/drbd/drbd_nl.c @@ -1915,6 +1915,7 @@ int drbd_adm_attach(struct sk_buff *skb, struct genl_info *info) static int adm_detach(struct drbd_device *device, int force) { enum drbd_state_rv retcode; + void *buffer; int ret; if (force) { @@ -1925,9 +1926,12 @@ static int adm_detach(struct drbd_device *device, int force) } drbd_suspend_io(device); /* so no-one is stuck in drbd_al_begin_io */ - drbd_md_get_buffer(device, __func__); /* make sure there is no in-flight meta-data IO */ - retcode = drbd_request_state(device, NS(disk, D_FAILED)); - drbd_md_put_buffer(device); + buffer = drbd_md_get_buffer(device, __func__); /* make sure there is no in-flight meta-data IO */ + if (buffer) { + retcode = drbd_request_state(device, NS(disk, D_FAILED)); + drbd_md_put_buffer(device); + } else /* already <= D_FAILED */ + retcode = SS_NOTHING_TO_DO; /* D_FAILED will transition to DISKLESS. */ drbd_resume_io(device); ret = wait_event_interruptible(device->misc_wait, -- 2.20.1