Stefan Jones wrote:
Made a standalone testcase, run this and the kernel will eat up your
memory (seen via slabtop):
[ creates a inotify_dev, and a watch and exits ; repeat via fork ... ]
Tracked it down me thinks:
struct inotify_device {
...
struct idr idr; /* idr mapping wd -> watch */
...
}
idr gets allocated each time inotify_init() is called:
asmlinkage long sys_inotify_init(void)
{
..
idr_init(&dev->idr);
..
}
Looking in lib/idr.c you see:
* You can release ids at any time. When all ids are released, most of
* the memory is returned (we keep IDR_FREE_MAX) in a local pool so we
* don't need to go to the memory "store" during an id allocate, just
* so you don't need to be too concerned about locking and conflicts
* with the slab allocator.
So even if you free all ids which create_watch->inotify_dev_get_wd
creates you will still have menory in your struct idr.
So when
static inline void put_inotify_dev(struct inotify_device *dev)
{
if (atomic_dec_and_test(&dev->count)) {
atomic_dec(&dev->user->inotify_devs);
free_uid(dev->user);
kfree(dev);
}
}
is called I think this is whre the memory gets lost. ( linux/idr.h has
not free function I see )
Stefan
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