[PATCH 2/3] alloc_tag: prevent enabling memory profiling if it was shut down

[Suren Baghdasaryan <surenb@google.com>]

Memory profiling can be shut down due to reasons like a failure during
initialization. When this happens, the user should not be able to
re-enable it. Current sysctrl interface does not handle this properly
and will allow re-enabling memory profiling. Fix this by checking for
this condition during sysctrl write operation.

Signed-off-by: Suren Baghdasaryan <surenb@google.com>
---
 lib/alloc_tag.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/lib/alloc_tag.c b/lib/alloc_tag.c
index 95688c4cba7a..79891528e7b6 100644
--- a/lib/alloc_tag.c
+++ b/lib/alloc_tag.c
@@ -767,6 +767,16 @@ struct page_ext_operations page_alloc_tagging_ops = {
 EXPORT_SYMBOL(page_alloc_tagging_ops);
 
 #ifdef CONFIG_SYSCTL
+static int proc_mem_profiling_handler(const struct ctl_table *table, int write,
+				      void *buffer, size_t *lenp, loff_t *ppos)
+{
+	if (!mem_profiling_support && write)
+		return -EINVAL;
+
+	return proc_do_static_key(table, write, buffer, lenp, ppos);
+}
+
+
 static struct ctl_table memory_allocation_profiling_sysctls[] = {
 	{
 		.procname	= "mem_profiling",
@@ -776,7 +786,7 @@ static struct ctl_table memory_allocation_profiling_sysctls[] = {
 #else
 		.mode		= 0644,
 #endif
-		.proc_handler	= proc_do_static_key,
+		.proc_handler	= proc_mem_profiling_handler,
 	},
 };
 
-- 
2.51.0.384.g4c02a37b29-goog