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authorLars Ellenberg <lars.ellenberg@linbit.com>2017-08-29 11:20:43 +0300
committerJens Axboe <axboe@kernel.dk>2017-08-30 00:34:45 +0300
commit33d32fa7120ed184efc9be1ea3c016109b4fea84 (patch)
tree30c0fdf900ecdfbf51207795eebc0d985a06effe /drivers/block/drbd/drbd_nl.c
parent427fd2bee0a33a670de186387e79d280a6808a66 (diff)
downloadlinux-33d32fa7120ed184efc9be1ea3c016109b4fea84.tar.xz
drbd: fix potential deadlock when trying to detach during handshake
When requesting a detach, we first suspend IO, and also inhibit meta-data IO by means of drbd_md_get_buffer(), because we don't want to "fail" the disk while there is IO in-flight: the transition into D_FAILED for detach purposes may get misinterpreted as actual IO error in a confused endio function. We wrap it all into wait_event(), to retry in case the drbd_req_state() returns SS_IN_TRANSIENT_STATE, as it does for example during an ongoing connection handshake. In that example, the receiver thread may need to grab drbd_md_get_buffer() during the handshake to make progress. To avoid potential deadlock with detach, detach needs to grab and release the meta data buffer inside of that wait_event retry loop. To avoid lock inversion between mutex_lock(&device->state_mutex) and drbd_md_get_buffer(device), introduce a new enum chg_state_flag CS_INHIBIT_MD_IO, and move the call to drbd_md_get_buffer() inside the state_mutex grabbed in drbd_req_state(). Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com> Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'drivers/block/drbd/drbd_nl.c')
-rw-r--r--drivers/block/drbd/drbd_nl.c25
1 files changed, 2 insertions, 23 deletions
diff --git a/drivers/block/drbd/drbd_nl.c b/drivers/block/drbd/drbd_nl.c
index c383b6cf272a..6bb58a6836ed 100644
--- a/drivers/block/drbd/drbd_nl.c
+++ b/drivers/block/drbd/drbd_nl.c
@@ -2149,34 +2149,13 @@ 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) {
set_bit(FORCE_DETACH, &device->flags);
drbd_force_state(device, NS(disk, D_FAILED));
- retcode = SS_SUCCESS;
- goto out;
+ return SS_SUCCESS;
}
- drbd_suspend_io(device); /* so no-one is stuck in drbd_al_begin_io */
- 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,
- device->state.disk != D_FAILED);
- if ((int)retcode == (int)SS_IS_DISKLESS)
- retcode = SS_NOTHING_TO_DO;
- if (ret)
- retcode = ERR_INTR;
-out:
- return retcode;
+ return drbd_request_detach_interruptible(device);
}
/* Detaching the disk is a process in multiple stages. First we need to lock