rss_stat: add support to detect RSS updates of external mm
When a process updates the RSS of a different process, the rss_stat
tracepoint appears in the context of the process doing the update. This
can confuse userspace that the RSS of process doing the update is
updated, while in reality a different process's RSS was updated.
This issue happens in reclaim paths such as with direct reclaim or
background reclaim.
This patch adds more information to the tracepoint about whether the mm
being updated belongs to the current process's context (curr field). We
also include a hash of the mm pointer so that the process who the mm
belongs to can be uniquely identified (mm_id field).
Also vsprintf.c is refactored a bit to allow reuse of hashing code.
[akpm@linux-foundation.org: remove unused local `str']
[joelaf@google.com: inline call to ptr_to_hashval]
Link: http://lore.kernel.org/r/20191113153816.14b95acd@gandalf.local.home
Link: http://lkml.kernel.org/r/20191114164622.GC233237@google.com
Link: http://lkml.kernel.org/r/20191106024452.81923-1-joel@joelfernandes.org
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Reported-by: Ioannis Ilkos <ilkos@google.com>
Acked-by: Petr Mladek <pmladek@suse.com> [lib/vsprintf.c]
Cc: Tim Murray <timmurray@google.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Carmen Jackson <carmenjackson@google.com>
Cc: Mayank Gupta <mayankgupta@google.com>
Cc: Daniel Colascione <dancol@google.com>
Cc: Steven Rostedt (VMware) <rostedt@goodmis.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Ralph Campbell <rcampbell@nvidia.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index dee8fc4..7c488a1 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -761,23 +761,12 @@ static int __init initialize_ptr_random(void)
early_initcall(initialize_ptr_random);
/* Maps a pointer to a 32 bit unique identifier. */
-static char *ptr_to_id(char *buf, char *end, const void *ptr,
- struct printf_spec spec)
+static inline int __ptr_to_hashval(const void *ptr, unsigned long *hashval_out)
{
- const char *str = sizeof(ptr) == 8 ? "(____ptrval____)" : "(ptrval)";
unsigned long hashval;
- /* When debugging early boot use non-cryptographically secure hash. */
- if (unlikely(debug_boot_weak_hash)) {
- hashval = hash_long((unsigned long)ptr, 32);
- return pointer_string(buf, end, (const void *)hashval, spec);
- }
-
- if (static_branch_unlikely(¬_filled_random_ptr_key)) {
- spec.field_width = 2 * sizeof(ptr);
- /* string length must be less than default_width */
- return error_string(buf, end, str, spec);
- }
+ if (static_branch_unlikely(¬_filled_random_ptr_key))
+ return -EAGAIN;
#ifdef CONFIG_64BIT
hashval = (unsigned long)siphash_1u64((u64)ptr, &ptr_key);
@@ -789,6 +778,35 @@ static char *ptr_to_id(char *buf, char *end, const void *ptr,
#else
hashval = (unsigned long)siphash_1u32((u32)ptr, &ptr_key);
#endif
+ *hashval_out = hashval;
+ return 0;
+}
+
+int ptr_to_hashval(const void *ptr, unsigned long *hashval_out)
+{
+ return __ptr_to_hashval(ptr, hashval_out);
+}
+
+static char *ptr_to_id(char *buf, char *end, const void *ptr,
+ struct printf_spec spec)
+{
+ const char *str = sizeof(ptr) == 8 ? "(____ptrval____)" : "(ptrval)";
+ unsigned long hashval;
+ int ret;
+
+ /* When debugging early boot use non-cryptographically secure hash. */
+ if (unlikely(debug_boot_weak_hash)) {
+ hashval = hash_long((unsigned long)ptr, 32);
+ return pointer_string(buf, end, (const void *)hashval, spec);
+ }
+
+ ret = __ptr_to_hashval(ptr, &hashval);
+ if (ret) {
+ spec.field_width = 2 * sizeof(ptr);
+ /* string length must be less than default_width */
+ return error_string(buf, end, str, spec);
+ }
+
return pointer_string(buf, end, (const void *)hashval, spec);
}