This adds a new notify channel to the transfuse protocol. It is not
optional yet but could be made to be optional. A notify protocol and
notify channel are required because writing FUSE response messages to
the FUSE device has different semantics from writing asynchronous
notifications. In particular, response message writes only error on
malformed messages, do not take locks, and do not block. In contrast,
asynchronous notifications can error under normal conditions
(e.g. invalidating a cache entry that doesn't exist), can take locks
during the write call, and can block.
If responses and notifications occur in the same thread, the file system
can become deadlocked when syscalls lock resources waiting for a
response and a notification is written that blocks attempting to acquire
those same locks. The response that would unlock the contended lock
could be queued behind the notification write but the notification write
can't unblock until the response is written in the future. This patch
enables file systems to avoid that fate by offering a secondary channel
on which to send notifications.
Signed-off-by: David Sheets <dsheets@docker.com>
As arm will not be a desktop edition, we will not need to
try to fix these. We do need `diagnostics` though, the
vsock code however is not cross building, needs to be fixed
or made conditional.
Signed-off-by: Justin Cormack <justin.cormack@docker.com>
From torvalds/linux@4192f672fa which was
part of torvalds/linux@v4.7-rc6. The change is purely to ensure that vsock
is lockdep-clean.
Signed-off-by: David Sheets <dsheets@docker.com>
AUFS introduces new lockdep relations which are beyond the maximum variants
that lockdep ships with. Without this patch, AUFS triggers lockdep BUG sanity
checks and disables lockdep for the rest of the system.
The present value of the patch is:
```diff
aufs4.4 lockdep patch
diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
index c57e424..4153563 100644
--- a/include/linux/lockdep.h
+++ b/include/linux/lockdep.h
@@ -29,7 +29,7 @@ extern int lock_stat;
*/
#define XXX_LOCK_USAGE_STATES (1+3*4)
-#define MAX_LOCKDEP_SUBCLASSES 8UL
+#define MAX_LOCKDEP_SUBCLASSES (8UL + 4)
/*
* NR_LOCKDEP_CACHING_CLASSES ... Number of classes
@@ -203,7 +203,7 @@ struct lock_chain {
u64 chain_key;
};
-#define MAX_LOCKDEP_KEYS_BITS 13
+#define MAX_LOCKDEP_KEYS_BITS (13 + 3)
/*
* Subtract one because we offset hlock->class_idx by 1 in order
* to make 0 mean no class. This avoids overflowing the class_idx
diff --git a/kernel/locking/lockdep_internals.h b/kernel/locking/lockdep_internals.h
index 51c4b24..fba7557 100644
--- a/kernel/locking/lockdep_internals.h
+++ b/kernel/locking/lockdep_internals.h
@@ -54,9 +54,9 @@ enum {
* table (if it's not there yet), and we check it for lock order
* conflicts and deadlocks.
*/
-#define MAX_LOCKDEP_ENTRIES 32768UL
+#define MAX_LOCKDEP_ENTRIES (32768UL << 5)
-#define MAX_LOCKDEP_CHAINS_BITS 16
+#define MAX_LOCKDEP_CHAINS_BITS (16 + 5)
#define MAX_LOCKDEP_CHAINS (1UL << MAX_LOCKDEP_CHAINS_BITS)
#define MAX_LOCKDEP_CHAIN_HLOCKS (MAX_LOCKDEP_CHAINS*5)
@@ -65,7 +65,7 @@ enum {
* Stack-trace: tightly packed array of stack backtrace
* addresses. Protected by the hash_lock.
*/
-#define MAX_STACK_TRACE_ENTRIES 524288UL
+#define MAX_STACK_TRACE_ENTRIES (524288UL << 5)
extern struct list_head all_lock_classes;
extern struct lock_chain lock_chains[];
```
Signed-off-by: David Sheets <dsheets@docker.com>
