mm/page_owner: record task command name

The page_owner information currently includes the pid of the calling
task.  That is useful as long as the task is still running.  Otherwise,
the number is meaningless.  To have more information about the
allocating tasks that had exited by the time the page_owner information
is retrieved, we need to store the command name of the task.

Add a new comm field into page_owner structure to store the command name
and display it when the page_owner information is retrieved.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Waiman Long <[email protected]>
Acked-by: Rafael Aquini <[email protected]>
Cc: Andy Shevchenko <[email protected]>
Cc: David Rientjes <[email protected]>
Cc: Ira Weiny <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Mike Rapoport <[email protected]>
Cc: Petr Mladek <[email protected]>
Cc: Rasmus Villemoes <[email protected]>
Cc: Roman Gushchin <[email protected]>
Cc: Sergey Senozhatsky <[email protected]>
Cc: Steven Rostedt (Google) <[email protected]>
Cc: Vladimir Davydov <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

1 files changed, 10 insertions, 4 deletions

diff --git a/mm/page_owner.c b/mm/page_owner.c
index f7820357e4d4..d56afa9c792e 100644
--- a/mm/page_owner.c
+++ b/mm/page_owner.c
@@ -29,6 +29,7 @@ struct page_owner {
 	depot_stack_handle_t free_handle;
 	u64 ts_nsec;
 	u64 free_ts_nsec;
+	char comm[TASK_COMM_LEN];
 	pid_t pid;
 };
 
@@ -165,6 +166,8 @@ static inline void __set_page_owner_handle(struct page_ext *page_ext,
 		page_owner->last_migrate_reason = -1;
 		page_owner->pid = current->pid;
 		page_owner->ts_nsec = local_clock();
+		strlcpy(page_owner->comm, current->comm,
+			sizeof(page_owner->comm));
 		__set_bit(PAGE_EXT_OWNER, &page_ext->flags);
 		__set_bit(PAGE_EXT_OWNER_ALLOCATED, &page_ext->flags);
 
@@ -232,6 +235,7 @@ void __folio_copy_owner(struct folio *newfolio, struct folio *old)
 	new_page_owner->pid = old_page_owner->pid;
 	new_page_owner->ts_nsec = old_page_owner->ts_nsec;
 	new_page_owner->free_ts_nsec = old_page_owner->ts_nsec;
+	strcpy(new_page_owner->comm, old_page_owner->comm);
 
 	/*
 	 * We don't clear the bit on the old folio as it's going to be freed
@@ -379,10 +383,11 @@ print_page_owner(char __user *buf, size_t count, unsigned long pfn,
 		return -ENOMEM;
 
 	ret = scnprintf(kbuf, count,
-			"Page allocated via order %u, mask %#x(%pGg), pid %d, ts %llu ns, free_ts %llu ns\n",
+			"Page allocated via order %u, mask %#x(%pGg), pid %d (%s), ts %llu ns, free_ts %llu ns\n",
 			page_owner->order, page_owner->gfp_mask,
 			&page_owner->gfp_mask, page_owner->pid,
-			page_owner->ts_nsec, page_owner->free_ts_nsec);
+			page_owner->comm, page_owner->ts_nsec,
+			page_owner->free_ts_nsec);
 
 	/* Print information relevant to grouping pages by mobility */
 	pageblock_mt = get_pageblock_migratetype(page);
@@ -449,9 +454,10 @@ void __dump_page_owner(const struct page *page)
 	else
 		pr_alert("page_owner tracks the page as freed\n");
 
-	pr_alert("page last allocated via order %u, migratetype %s, gfp_mask %#x(%pGg), pid %d, ts %llu, free_ts %llu\n",
+	pr_alert("page last allocated via order %u, migratetype %s, gfp_mask %#x(%pGg), pid %d (%s), ts %llu, free_ts %llu\n",
 		 page_owner->order, migratetype_names[mt], gfp_mask, &gfp_mask,
-		 page_owner->pid, page_owner->ts_nsec, page_owner->free_ts_nsec);
+		 page_owner->pid, page_owner->comm, page_owner->ts_nsec,
+		 page_owner->free_ts_nsec);
 
 	handle = READ_ONCE(page_owner->handle);
 	if (!handle)