linux-toradex.git/fs/dlm/ast.c, branch v6.7

fs: dlm: move dlm_purge_lkb_callbacks to user module

2023-06-14T15:17:33+00:00

This patch moves the dlm_purge_lkb_callbacks() function from ast to user
dlm module as it is only a function being used by dlm user
implementation. I got be hinted to hold specific locks regarding the
callback handling for dlm_purge_lkb_callbacks() but it was false
positive. It is confusing because ast dlm implementation uses a
different locking behaviour as user locks uses as DLM handles kernel and
user dlm locks differently. To avoid the confusing we move this function
to dlm user implementation.

Signed-off-by: Alexander Aring 
Signed-off-by: David Teigland

fs: dlm: clear pending bit when queue was empty

2023-06-14T15:17:33+00:00

This patch clears the DLM_IFL_CB_PENDING_BIT flag which will be set when
there is callback work queued when there was no callback to dequeue. It
is a buggy case and should never happen, that's why there is a
WARN_ON(). However if the case happens we are prepared to somehow
recover from it.

Cc: stable@vger.kernel.org
Fixes: 61bed0baa4db ("fs: dlm: use a non-static queue for callbacks")
Signed-off-by: Alexander Aring 
Signed-off-by: David Teigland

fs: dlm: change dflags to use atomic bits

2023-03-06T21:49:07+00:00

Currently manipulating lkb_dflags assumes to held the rsb lock assigned
to the lkb. This is held by dlm message processing after certain
time to lookup the right rsb from the received lkb message id. For user
space locks flags, which is currently the only use case for lkb_dflags,
flags are also being set during dlm character device handling without
holding the rsb lock. To minimize the risk that bit operations are
getting corrupted we switch to atomic bit operations. This patch will
also introduce helpers to snapshot atomic bit values in an non atomic
way. There might be still issues with the flag handling e.g. running in
case of manipulating bit ops and snapshot them at the same time, but this
patch minimize them and will start to use atomic bit operations.

Signed-off-by: Alexander Aring 
Signed-off-by: David Teigland

fs: dlm: store lkb distributed flags into own value

2023-03-06T21:49:07+00:00

This patch stores lkb distributed flags value in an separate value
instead of sharing internal and distributed flags in lkb->lkb_flags value.
This has the advantage to not mask/write back flag values in
receive_flags() functionality. The dlm debug_fs does not provide the
distributed flags anymore, those can be added in future.

Signed-off-by: Alexander Aring 
Signed-off-by: David Teigland

fs: dlm: fix DLM_IFL_CB_PENDING gets overwritten

2023-03-06T21:49:07+00:00

This patch introduce a new internal flag per lkb value to handle
internal flags which are handled not on wire. The current lkb internal
flags stored as lkb->lkb_flags are split in upper and lower bits, the
lower bits are used to share internal flags over wire for other cluster
wide lkb copies on other nodes.

In commit 61bed0baa4db ("fs: dlm: use a non-static queue for callbacks")
we introduced a new internal flag for pending callbacks for the dlm
callback queue. This flag is protected by the lkb->lkb_cb_lock lock.
This patch overlooked that on dlm receive path and the mentioned upper
and lower bits, that dlm will read the flags, mask it and write it
back. As example receive_flags() in fs/dlm/lock.c. This flag
manipulation is not done atomically and is not protected by
lkb->lkb_cb_lock. This has unknown side effects of the current callback
handling.

In future we should move to set/clear/test bit functionality and avoid
read, mask and writing back flag values. In later patches we will move
the upper parts to the new introduced internal lkb flags which are not
shared between other cluster nodes to the new non shared internal flag
field to avoid similar issues.

Cc: stable@vger.kernel.org
Fixes: 61bed0baa4db ("fs: dlm: use a non-static queue for callbacks")
Reported-by: Bob Peterson 
Signed-off-by: Alexander Aring 
Signed-off-by: David Teigland

fs: dlm: rename DLM_IFL_NEED_SCHED to DLM_IFL_CB_PENDING

2022-11-21T15:45:49+00:00

This patch renames DLM_IFL_NEED_SCHED to DLM_IFL_CB_PENDING because
CB_PENDING is a proper name to describe this flag. This flag is set when
callback enqueue will return DLM_ENQUEUE_CALLBACK_NEED_SCHED because the
callback worker need to be queued. The flag tells that callbacks are
currently pending to be called and will be unset if the callback work
for the specific lkb is done. The term need schedule is part of this
time but a proper name is to say that there are some callbacks pending
to being called.

Signed-off-by: Alexander Aring 
Signed-off-by: David Teigland

fs: dlm: ast do WARN_ON_ONCE() on hotpath

2022-11-21T15:45:49+00:00

This patch changes the ast hotpath functionality in very unlikely cases
that we do WARN_ON_ONCE() instead of WARN_ON() to not spamming the
console output if we run into states that it would occur over and over
again.

Signed-off-by: Alexander Aring 
Signed-off-by: David Teigland

fs: dlm: drop lkb ref in bug case

2022-11-21T15:45:49+00:00

This patch will drop the lkb reference in an very unlikely case which
should in practice not happened. However if it happens we cleanup the
reference just in case.

Signed-off-by: Alexander Aring 
Signed-off-by: David Teigland

fs: dlm: use a non-static queue for callbacks

2022-11-08T18:59:41+00:00

This patch will introducde a queue implementation for callbacks by using
the Linux lists. The current callback queue handling is implemented by a
static limit of 6 entries, see DLM_CALLBACKS_SIZE. The sequence number
inside the callback structure was used to see if the entries inside the
static entry is valid or not. We don't need any sequence numbers anymore
with a dynamic datastructure with grows and shrinks during runtime to
offer such functionality.

We assume that every callback will be delivered to the DLM user if once
queued. Therefore the callback flag DLM_CB_SKIP was dropped and the
check for skipping bast was moved before worker handling and not skip
while the callback worker executes. This will reduce unnecessary queues
of the callback worker.

All last callback saves are pointers now and don't need to copied over.
There is a reference counter for callback structures which will care
about to free the callback structures at the right time if they are not
referenced anymore.

Signed-off-by: Alexander Aring 
Signed-off-by: David Teigland

fs: dlm: move last cast bast time to function call

2022-11-08T18:59:41+00:00

This patch moves the debugging information of the last cast and bast
time when calling the last and bast function call.

Signed-off-by: Alexander Aring 
Signed-off-by: David Teigland