Currently if kmemleak is disabled, the kmemleak objects can never be freed,
no matter if it's disabled by a user or due to fatal errors.
Those objects can be a big waste of memory.
OBJS ACTIVE USE OBJ SIZE SLABS OBJ/SLAB CACHE SIZE NAME
1200264 1197433 99% 0.30K 46164 26 369312K kmemleak_object
With this patch, internal objects will be freed immediately if kmemleak is
disabled explicitly by a user. If it's disabled due to a kmemleak error,
The user will be informed, and then he/she can reclaim memory with:
# echo off > /sys/kernel/debug/kmemleak
v2: use "off" handler instead of "clear" handler to do this, suggested
by Catalin.
Signed-off-by: Li Zefan <lizefan@xxxxxxxxxx>
---
Documentation/kmemleak.txt | 14 +++++++++++++-
mm/kmemleak.c | 21 ++++++++++++++++-----
2 files changed, 29 insertions(+), 6 deletions(-)
diff --git a/Documentation/kmemleak.txt b/Documentation/kmemleak.txt
index 6dc8013..00aa013 100644
--- a/Documentation/kmemleak.txt
+++ b/Documentation/kmemleak.txt
@@ -42,7 +42,8 @@ objects to be reported as orphan.
Memory scanning parameters can be modified at run-time by writing to the
/sys/kernel/debug/kmemleak file. The following parameters are supported:
- off - disable kmemleak (irreversible)
+ off - disable kmemleak, or free all kmemleak objects if kmemleak
+ has been disabled due to fatal errors. (irreversible).
stack=on - enable the task stacks scanning (default)
stack=off - disable the tasks stacks scanning
scan=on - start the automatic memory scanning thread (default)
@@ -118,6 +119,17 @@ Then as usual to get your report with:
# cat /sys/kernel/debug/kmemleak
+Freeing kmemleak internal objects
+---------------------------------
+
+To allow access to previously found memory leaks even when an error fatal
+to kmemleak happens, internal kmemleak objects won't be freed in this case.
+Those objects may occupy a large part of physical memory.
+
+You can reclaim memory from those objects with:
+
+ # echo off > /sys/kernel/debug/kmemleak
+
Kmemleak API
------------
diff --git a/mm/kmemleak.c b/mm/kmemleak.c
index 31f01c5..7fc030e 100644
--- a/mm/kmemleak.c
+++ b/mm/kmemleak.c
@@ -1616,9 +1616,6 @@ static ssize_t kmemleak_write(struct file *file, const char __user *user_buf,
int buf_size;
int ret;
- if (!atomic_read(&kmemleak_enabled))
- return -EBUSY;
-
buf_size = min(size, (sizeof(buf) - 1));
if (strncpy_from_user(buf, user_buf, buf_size) < 0)
return -EFAULT;
@@ -1628,9 +1625,18 @@ static ssize_t kmemleak_write(struct file *file, const char __user *user_buf,
if (ret < 0)
return ret;
- if (strncmp(buf, "off", 3) == 0)
+ if (strncmp(buf, "off", 3) == 0) {
+ stop_scan_thread();
kmemleak_disable();
- else if (strncmp(buf, "stack=on", 8) == 0)
+ goto out;
+ }
+
+ if (!atomic_read(&kmemleak_enabled)) {
+ ret = -EBUSY;
+ goto out;
+ }
+
+ if (strncmp(buf, "stack=on", 8) == 0)
kmemleak_stack_scan = 1;
else if (strncmp(buf, "stack=off", 9) == 0)
kmemleak_stack_scan = 0;
@@ -1695,6 +1701,11 @@ static void kmemleak_do_cleanup(struct work_struct *work)
list_for_each_entry_rcu(object, &object_list, object_list)
delete_object_full(object->pointer);
rcu_read_unlock();
+ } else {
+ pr_info("Disable kmemleak without freeing internal objects, "
+ "so you may still check information on memory leak. "
+ "You may reclaim memory by writing \"off\" to "
+ "/sys/kernel/debug/kmemleak\n");
}
mutex_unlock(&scan_mutex);
}
--
1.8.0.2
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