On Mon, 28 Mar 2011, Bob Liu wrote:
> On no-mmu arch, there is a memleak duirng shmem test.
> The cause of this memleak is ramfs_nommu_expand_for_mapping() added page
> refcount to 2 which makes iput() can't free that pages.
>
> The simple test file is like this:
> int main(void)
> {
> int i;
> key_t k = ftok("/etc", 42);
>
> for ( i=0; i<100; ++i) {
> int id = shmget(k, 10000, 0644|IPC_CREAT);
> if (id == -1) {
> printf("shmget error\n");
> }
> if(shmctl(id, IPC_RMID, NULL ) == -1) {
> printf("shm rm error\n");
> return -1;
> }
> }
> printf("run ok...\n");
> return 0;
> }
>
> And the result:
> root:/> free
> total used free shared buffers
> Mem: 60320 16644 43676 0 0
> -/+ buffers: 16644 43676
> root:/> shmem
> run ok...
> root:/> free
> total used free shared buffers
> Mem: 60320 17912 42408 0 0
> -/+ buffers: 17912 42408
> root:/> shmem
> run ok...
> root:/> free
> total used free shared buffers
> Mem: 60320 19096 41224 0 0
> -/+ buffers: 19096 41224
> root:/> shmem
> run ok...
> root:/> free
> total used free shared buffers
> Mem: 60320 20296 40024 0 0
> -/+ buffers: 20296 40024
> root:/> shmem
> run ok...
> root:/> free
> total used free shared buffers
> Mem: 60320 21496 38824 0 0
> -/+ buffers: 21496 38824
> root:/> shmem
> run ok...
> root:/> free
> total used free shared buffers
> Mem: 60320 22692 37628 0 0
> -/+ buffers: 22692 37628
> root:/>
>
> After this patch the test result is:(no memleak anymore)
> root:/>
> root:/> free
> total used free shared buffers
> Mem: 60320 16580 43740 0 0
> -/+ buffers: 16580 43740
> root:/> shmem
> run ok...
> root:/> free
> total used free shared buffers
> Mem: 60320 16668 43652 0 0
> -/+ buffers: 16668 43652
> root:/> shmem
> run ok...
> root:/> free
> total used free shared buffers
> Mem: 60320 16668 43652 0 0
> -/+ buffers: 16668 43652
> root:/> shmem
> run ok...
> root:/> free
> total used free shared buffers
> Mem: 60320 16668 43652 0 0
> -/+ buffers: 16668 43652
> root:/> shmem
> run ok...
> root:/> free
> total used free shared buffers
> Mem: 60320 16668 43652 0 0
> -/+ buffers: 16668 43652
> root:/> shmem
> run ok...
> root:/> free
> total used free shared buffers
> Mem: 60320 16668 43652 0 0
> -/+ buffers: 16668 43652
> root:/>
>
> Signed-off-by: Bob Liu <lliubbo@xxxxxxxxx>
Acked-by: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: stable@xxxxxxxxxx
Sorry for being so slow to get back to this, Bob.
And I'm sorry that in my original patch for it, I just couldn't
resist a little tidying up while I was there: which led Paul to
observe correctly that the function would be better off using
alloc_pages_exact(); which made me pause before responding,
seeing a proposal to rename that to get_free_pages_exact().
Aaaaaah, let's go with your patch below, which fixes the bug in
the simplest fashion; and do any tidying up at leisure later on.
I see Andrew is questioning the correctness of this patch:
let me answer his mail separately.
Hugh
> ---
> fs/ramfs/file-nommu.c | 1 +
> 1 files changed, 1 insertions(+), 0 deletions(-)
>
> diff --git a/fs/ramfs/file-nommu.c b/fs/ramfs/file-nommu.c
> index 9eead2c..fbb0b47 100644
> --- a/fs/ramfs/file-nommu.c
> +++ b/fs/ramfs/file-nommu.c
> @@ -112,6 +112,7 @@ int ramfs_nommu_expand_for_mapping(struct inode *inode, size_t newsize)
> SetPageDirty(page);
>
> unlock_page(page);
> + put_page(page);
> }
>
> return 0;
> --
> 1.6.3.3
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