ceph: let osd client clean up for interrupted request

In ceph_sync_write(), if a safe callback is supplied with a request,
and an error is returned by ceph_osdc_wait_request(), a block of
code is executed to remove the request from the unsafe writes list
and drop references to capabilities acquired just prior to a call to
ceph_osdc_wait_request().

The only function used for this callback is sync_write_commit(),
and it does *exactly* what that block of error handling code does.

Now in ceph_osdc_wait_request(), if an error occurs (due to an
interupt during a wait_for_completion_interruptible() call),
complete_request() gets called, and that calls the request's
safe_callback method if it's defined.

So this means that this cleanup activity gets called twice in this
case, which is erroneous (and in fact leads to a crash).

Fix this by just letting the osd client handle the cleanup in
the event of an interrupt.

This resolves one problem mentioned in:
    http://tracker.ceph.com/issues/4706

Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Yan, Zheng <zheng.z.yan@intel.com>

fs/ceph/file.c

@@ -595,12 +595,6 @@ more:
 		}
 		
 		ret = ceph_osdc_wait_request(&fsc->client->osdc, req);
-		if (ret < 0 && req->r_safe_callback) {
-			spin_lock(&ci->i_unsafe_lock);
-			list_del_init(&req->r_unsafe_item);
-			spin_unlock(&ci->i_unsafe_lock);
-			ceph_put_cap_refs(ci, CEPH_CAP_FILE_WR);
-		}
 	}
 
 	if (file->f_flags & O_DIRECT)