wcfs: tests: Allow to adjust tDB.assertBlk timeout

Currently assertBlk uses default timeout() to wait for READ operation to
complete. That works well everywhere except that in faulty
protection tests wcfs server will first need to wait for its own
pintimeout time to kill the faulty client and only then	return read
result to all non-faulty clients.

This way corresponding test, when one client fails to handle pin
notification well triggered due to READ operations, will need to use
adjusted longer timeout for the good client when doing assertBlk.

Adjust assertBlk to allow specifying custom timeout as preparatory step
for that.

/reviewed-by @levin.zimmermann
/reviewed-on !18

wcfs/wcfs_test.py

@@ -300,11 +300,13 @@ def start_and_crash_wcfs(zurl, mntpt): # -> WCFS
 
 # many tests need to be run with some reasonable timeout to detect lack of wcfs
 # response. with_timeout and timeout provide syntactic shortcuts to do so.
-def with_timeout(parent=context.background()):  # -> ctx, cancel
-    return context.with_timeout(parent, 3*time.second)
+def with_timeout(parent=context.background(), dt=None):  # -> ctx, cancel
+    if dt is None:
+        dt = 3*time.second
+    return context.with_timeout(parent, dt)
 
-def timeout(parent=context.background()):   # -> ctx
-    ctx, _ = with_timeout()
+def timeout(parent=context.background(), dt=None):   # -> ctx
+    ctx, _ = with_timeout(parent, dt)
     return ctx
 
 # tdelay is used in places where we need to delay a bit in order to e.g.
@@ -798,8 +800,11 @@ class tFile:
     #
     # The automatic computation of pinokByWLink is verified against explicitly
     # provided pinokByWLink when it is present.
+    #
+    # The whole read operation must complete in specified time.
+    # The default timeout is used if timeout is not explicitly given.
     @func
-    def assertBlk(t, blk, dataok, pinokByWLink=None):
+    def assertBlk(t, blk, dataok, pinokByWLink=None, timeout=None):
         # TODO -> assertCtx('blk #%d' % blk)
         def _():
             assertCtx = 'blk #%d' % blk
@@ -812,10 +817,10 @@ class tFile:
         dataok = b(dataok)
         blkdata, _ = t.tdb._blkDataAt(t.zf, blk, t.at)
         assert blkdata == dataok, "computed vs explicit data"
-        t._assertBlk(blk, dataok, pinokByWLink)
+        t._assertBlk(blk, dataok, pinokByWLink, timeout=timeout)
 
     @func
-    def _assertBlk(t, blk, dataok, pinokByWLink=None, pinfunc=None):
+    def _assertBlk(t, blk, dataok, pinokByWLink=None, pinfunc=None, timeout=None):
         assert len(dataok) <= t.blksize
         dataok += b'\0'*(t.blksize - len(dataok))   # tailing zeros
         assert blk < t._sizeinblk()
@@ -863,6 +868,9 @@ class tFile:
             pinokByWLink[wlink] = (t.zf, pinok)
 
         # access 1 byte on the block and verify that wcfs sends us correct pins
+        ctx, cancel = with_timeout(t.tdb.ctx, timeout)
+        defer(cancel)
+
         blkview = t._blk(blk)
         assert t.cached()[blk] == cached
 
@@ -901,7 +909,7 @@ class tFile:
             b = _rx
 
             ev.append('read ' + b)
-        ev = doCheckingPin(_, pinokByWLink, pinfunc)
+        ev = doCheckingPin(ctx, _, pinokByWLink, pinfunc)
 
         # XXX hack - wlinks are notified and emit events simultaneously - we
         # check only that events begin and end with read pre/post and that pins
@@ -1119,7 +1127,7 @@ def _watch(twlink, zf, at, pinok, replyok):
         else:
             assert reply == replyok
 
-    doCheckingPin(_, {twlink: (zf, pinok)})
+    doCheckingPin(timeout(twlink.tdb.ctx), _, {twlink: (zf, pinok)})
 
 
 # doCheckingPin calls f and verifies that wcfs sends expected pins during the
@@ -1131,14 +1139,14 @@ def _watch(twlink, zf, at, pinok, replyok):
 #
 # pinfunc is called after pin request is received from wcfs, but before pin ack
 # is replied back. Pinfunc must not block.
-def doCheckingPin(f, pinokByWLink, pinfunc=None): # -> []event(str)
+def doCheckingPin(ctx, f, pinokByWLink, pinfunc=None): # -> []event(str)
     # call f and check that we receive pins as specified.
     # Use timeout to detect wcfs replying less pins than expected.
     #
     # XXX detect not sent pins via ack'ing previous pins as they come in (not
     # waiting for all of them) and then seeing that we did not received expected
     # pin when f completes?
-    ctx, cancel = with_timeout()
+    ctx, cancel = context.with_cancel(ctx)
     wg = sync.WorkGroup(ctx)
     ev = []