cxl: Keep track of mm struct associated with a context

The mm_struct corresponding to the current task is acquired each time
an interrupt is raised. So to simplify the code, we only get the
mm_struct when attaching an AFU context to the process.
The mm_count reference is increased to ensure that the mm_struct can't
be freed. The mm_struct will be released when the context is detached.
A reference on mm_users is not kept to avoid a circular dependency if
the process mmaps its cxl mmio and forget to unmap before exiting.
The field glpid (pid of the group leader associated with the pid), of
the structure cxl_context, is removed because it's no longer useful.

Signed-off-by: Christophe Lombard <clombard@linux.vnet.ibm.com>
Reviewed-by: Andrew Donnellan <andrew.donnellan@au1.ibm.com>
Acked-by: Frederic Barrat <fbarrat@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

1 files changed, 2 insertions, 10 deletions

diff --git a/drivers/misc/cxl/main.c b/drivers/misc/cxl/main.c
index b0b6ed31918e..1703655072b1 100644
--- a/drivers/misc/cxl/main.c
+++ b/drivers/misc/cxl/main.c
@@ -59,16 +59,10 @@ int cxl_afu_slbia(struct cxl_afu *afu)
 
 static inline void _cxl_slbia(struct cxl_context *ctx, struct mm_struct *mm)
 {
-	struct task_struct *task;
 	unsigned long flags;
-	if (!(task = get_pid_task(ctx->pid, PIDTYPE_PID))) {
-		pr_devel("%s unable to get task %i\n",
-			 __func__, pid_nr(ctx->pid));
-		return;
-	}
 
-	if (task->mm != mm)
-		goto out_put;
+	if (ctx->mm != mm)
+		return;
 
 	pr_devel("%s matched mm - card: %i afu: %i pe: %i\n", __func__,
 		 ctx->afu->adapter->adapter_num, ctx->afu->slice, ctx->pe);
@@ -79,8 +73,6 @@ static inline void _cxl_slbia(struct cxl_context *ctx, struct mm_struct *mm)
 	spin_unlock_irqrestore(&ctx->sste_lock, flags);
 	mb();
 	cxl_afu_slbia(ctx->afu);
-out_put:
-	put_task_struct(task);
 }
 
 static inline void cxl_slbia_core(struct mm_struct *mm)