Hi,
this patchset consists of a fixup by an error that was reported by intel
robot, where it seems to be that by the time page_owner gets
initialized, stackdepot has already depleted its allocation space and
returns 0-handles, turning that into null stack_records when trying
to retrieve the stack_record.
I was not able to reproduce that from the config because it booted fine
for me, but when setting e.g: dummy_handle to 0 artificially,
I could see the same error that was reported.
The second patch is a cleanup that can also lead to a compilation
warning.
Oscar Salvador (2):
mm,page_owner: Check for null stack_record before bumping its refcount
mm,page_owner: Drop unnecesary check
mm/page_owner.c | 12 ++++++++----
1 file changed, 8 insertions(+), 4 deletions(-)
--
2.44.0
Although the retrieval of the stack_records for {dummy,failure}_handle
happen when page_owner gets initialized, there seems to be some situations
where stackdepot space has been already depleted by then, so we get
0-handles which make stack_records being NULL for those cases.
Be careful to 1) only bump stack_records refcount and 2) only access
stack_record fields if we actually have a non-null stack_record between
hands.
Reported-by: kernel test robot <[email protected]>
Closes: https://lore.kernel.org/oe-lkp/[email protected]
Fixes: 4bedfb314bdd ("mm,page_owner: implement the tracking of the stacks count")
Signed-off-by: Oscar Salvador <[email protected]>
---
mm/page_owner.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)
diff --git a/mm/page_owner.c b/mm/page_owner.c
index 033e349f6479..7163a1c44ccf 100644
--- a/mm/page_owner.c
+++ b/mm/page_owner.c
@@ -107,8 +107,10 @@ static __init void init_page_owner(void)
/* Initialize dummy and failure stacks and link them to stack_list */
dummy_stack.stack_record = __stack_depot_get_stack_record(dummy_handle);
failure_stack.stack_record = __stack_depot_get_stack_record(failure_handle);
- refcount_set(&dummy_stack.stack_record->count, 1);
- refcount_set(&failure_stack.stack_record->count, 1);
+ if (dummy_stack.stack_record)
+ refcount_set(&dummy_stack.stack_record->count, 1);
+ if (failure_stack.stack_record)
+ refcount_set(&failure_stack.stack_record->count, 1);
dummy_stack.next = &failure_stack;
stack_list = &dummy_stack;
}
@@ -856,6 +858,9 @@ static int stack_print(struct seq_file *m, void *v)
unsigned long nr_entries;
struct stack_record *stack_record = stack->stack_record;
+ if (!stack->stack_record)
+ return 0;
+
nr_entries = stack_record->size;
entries = stack_record->entries;
stack_count = refcount_read(&stack_record->count) - 1;
--
2.44.0
stackdepot only saves stack_records which size is greather than 0,
so we cannot possibly have empty stack_records.
Drop the check.
Signed-off-by: Oscar Salvador <[email protected]>
---
mm/page_owner.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/mm/page_owner.c b/mm/page_owner.c
index 7163a1c44ccf..e7139952ffd9 100644
--- a/mm/page_owner.c
+++ b/mm/page_owner.c
@@ -865,8 +865,7 @@ static int stack_print(struct seq_file *m, void *v)
entries = stack_record->entries;
stack_count = refcount_read(&stack_record->count) - 1;
- if (!nr_entries || nr_entries < 0 || stack_count < 1 ||
- stack_count < page_owner_stack_threshold)
+ if (stack_count < 1 || stack_count < page_owner_stack_threshold)
return 0;
for (i = 0; i < nr_entries; i++)
--
2.44.0
On 3/6/24 13:32, Oscar Salvador wrote:
> Although the retrieval of the stack_records for {dummy,failure}_handle
> happen when page_owner gets initialized, there seems to be some situations
> where stackdepot space has been already depleted by then, so we get
> 0-handles which make stack_records being NULL for those cases.
>
> Be careful to 1) only bump stack_records refcount and 2) only access
> stack_record fields if we actually have a non-null stack_record between
> hands.
>
> Reported-by: kernel test robot <[email protected]>
> Closes: https://lore.kernel.org/oe-lkp/[email protected]
> Fixes: 4bedfb314bdd ("mm,page_owner: implement the tracking of the stacks count")
> Signed-off-by: Oscar Salvador <[email protected]>
Reviewed-by: Vlastimil Babka <[email protected]>
> ---
> mm/page_owner.c | 9 +++++++--
> 1 file changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/mm/page_owner.c b/mm/page_owner.c
> index 033e349f6479..7163a1c44ccf 100644
> --- a/mm/page_owner.c
> +++ b/mm/page_owner.c
> @@ -107,8 +107,10 @@ static __init void init_page_owner(void)
> /* Initialize dummy and failure stacks and link them to stack_list */
> dummy_stack.stack_record = __stack_depot_get_stack_record(dummy_handle);
> failure_stack.stack_record = __stack_depot_get_stack_record(failure_handle);
> - refcount_set(&dummy_stack.stack_record->count, 1);
> - refcount_set(&failure_stack.stack_record->count, 1);
> + if (dummy_stack.stack_record)
> + refcount_set(&dummy_stack.stack_record->count, 1);
> + if (failure_stack.stack_record)
> + refcount_set(&failure_stack.stack_record->count, 1);
> dummy_stack.next = &failure_stack;
> stack_list = &dummy_stack;
> }
> @@ -856,6 +858,9 @@ static int stack_print(struct seq_file *m, void *v)
> unsigned long nr_entries;
> struct stack_record *stack_record = stack->stack_record;
>
> + if (!stack->stack_record)
> + return 0;
> +
> nr_entries = stack_record->size;
> entries = stack_record->entries;
> stack_count = refcount_read(&stack_record->count) - 1;
On 3/6/24 13:32, Oscar Salvador wrote:
> stackdepot only saves stack_records which size is greather than 0,
> so we cannot possibly have empty stack_records.
> Drop the check.
>
> Signed-off-by: Oscar Salvador <[email protected]>
Reviewed-by: Vlastimil Babka <[email protected]>---
> mm/page_owner.c | 3 +--
> 1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/mm/page_owner.c b/mm/page_owner.c
> index 7163a1c44ccf..e7139952ffd9 100644
> --- a/mm/page_owner.c
> +++ b/mm/page_owner.c
> @@ -865,8 +865,7 @@ static int stack_print(struct seq_file *m, void *v)
> entries = stack_record->entries;
> stack_count = refcount_read(&stack_record->count) - 1;
>
> - if (!nr_entries || nr_entries < 0 || stack_count < 1 ||
> - stack_count < page_owner_stack_threshold)
> + if (stack_count < 1 || stack_count < page_owner_stack_threshold)
> return 0;
>
> for (i = 0; i < nr_entries; i++)