| Message ID | 1461755458-29225-41-git-send-email-hare@suse.de (mailing list archive) |
|---|---|
| State | Not Applicable, archived |
| Headers | show |
On Wed, Apr 27, 2016 at 01:10:41PM +0200, Hannes Reinecke wrote: I usually try to follow the lead of the cookie using-code of the lvm2 library, and that doesn't call udev_complete() on dm_task_set_cookie() failures. However, it does look like there is a possible problem with dm_task_set_cookie -> _udev_notify_sem_inc -> semctl(semid, 0, GETVAL) or dm_task_set_cookie -> _udev_notify_sem_create -> semctl(gen_semid, 0, GETVAL) or later failing. If that happens, the semaphore stays incremented, and dm_task_set_cookie returns failure. In the general case it could be risky to call udev_complete when dm_task_set_cookie failed. The semaphore might have not gotten incremented, and if we were doing multiple operations with the cookie, we might not wait for all of them any more. But the way multipath is using cookies, I think this is always safe. At worst, it won't be necessary, and we'll do nothing. But this should probably get fixed in the libdevmapper code, so that when dm_task_set_cookie fails, in cleans up any partial operations. ACK (we can pull these back out when it's been sorted in libdevmapper) -Ben > >From my understanding we should be calling udev_complete() on > a cookie if dm_task_set_cookie() failed. > > Signed-off-by: Hannes Reinecke <hare@suse.com> > --- > libmultipath/devmapper.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/libmultipath/devmapper.c b/libmultipath/devmapper.c > index c2ae83b..b10f9e6 100644 > --- a/libmultipath/devmapper.c > +++ b/libmultipath/devmapper.c > @@ -1440,8 +1440,10 @@ dm_rename (const char * old, char * new) > dm_task_no_open_count(dmt); > > if (!dm_task_set_cookie(dmt, &cookie, > - DM_UDEV_DISABLE_LIBRARY_FALLBACK)) > + DM_UDEV_DISABLE_LIBRARY_FALLBACK)) { > + dm_udev_complete(cookie); > goto out; > + } > r = dm_task_run(dmt); > > if (!r) > -- > 2.6.6 -- dm-devel mailing list dm-devel@redhat.com https://www.redhat.com/mailman/listinfo/dm-devel
diff --git a/libmultipath/devmapper.c b/libmultipath/devmapper.c index c2ae83b..b10f9e6 100644 --- a/libmultipath/devmapper.c +++ b/libmultipath/devmapper.c @@ -1440,8 +1440,10 @@ dm_rename (const char * old, char * new) dm_task_no_open_count(dmt); if (!dm_task_set_cookie(dmt, &cookie, - DM_UDEV_DISABLE_LIBRARY_FALLBACK)) + DM_UDEV_DISABLE_LIBRARY_FALLBACK)) { + dm_udev_complete(cookie); goto out; + } r = dm_task_run(dmt); if (!r)