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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 <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
This commit is contained in:
Lars Ellenberg 2015-02-25 19:37:28 +01:00 committed by Jens Axboe
parent 2b479766ee
commit 6434f404b4
1 changed files with 7 additions and 3 deletions
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10
drivers/block/drbd/drbd_nl.c
View File

@ -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,