bpf: Implement prealloc for task_local_storage
task_local_storage currently does not support pre-allocation and the memory
is allocated on demand using the GFP_ATOMIC mask. While atomic allocations
succeed most of the time and the occasional failures aren't a problem for
many use-cases, there are some which can benefit from reliable allocations -
e.g. tracking acquisitions and releases of specific resources to root cause
long-term reference leaks.
Prealloc semantics for task_local_storage:
* When a prealloc map is created, the map's elements for all existing tasks
are allocated.
* Afterwards, whenever a new task is forked, it automatically allocates the
elements for the existing preallocated maps.
To synchronize against concurrent forks, CONFIG_BPF_SYSCALL now enables
CONFIG_THREADGROUP_RWSEM and prealloc task_local_storage creation path
write-locks threadgroup_rwsem, and the rest of the implementation is
straight-forward.
Signed-off-by: Tejun Heo <tj@kernel.org>
8 files changed
