Re: [PATCH 5/5] Account certain kmem allocations to memcg

[Michal Hocko]

On Sat 07-11-15 23:07:09, Vladimir Davydov wrote:
> This patch marks those kmem allocations that are known to be easily
> triggered from userspace as __GFP_ACCOUNT, which makes them accounted to
> memcg. For the list, see below:
> 
>  - threadinfo
>  - task_struct
>  - task_delay_info
>  - pid
>  - cred
>  - mm_struct
>  - vm_area_struct and vm_region (nommu)
>  - anon_vma and anon_vma_chain
>  - signal_struct
>  - sighand_struct
>  - fs_struct
>  - files_struct
>  - fdtable and fdtable->full_fds_bits
>  - dentry and external_name
>  - inode for all filesystems. This is the most tedious part, because
>    most filesystems overwrite the alloc_inode method. Looks like using
>    __GFP_ACCOUNT in alloc_inode is going to become a new rule, like
>    passing SLAB_RECLAIM_ACCOUNT on inode cache creation.

I am wondering whether using a helper function to allocate an inode
cache would help in that regards. It would limit __GFP_ACCOUNT
penetration into fs code.

pipe buffers are trivial to abuse (e.g. via fd passing) so we want to
cap those as well. The following should do the trick AFAICS.
---
diff --git a/fs/pipe.c b/fs/pipe.c
index 8865f7963700..c4b7e8c08362 100644
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -590,7 +590,7 @@ struct pipe_inode_info *alloc_pipe_info(void)
 
 	pipe = kzalloc(sizeof(struct pipe_inode_info), GFP_KERNEL);
 	if (pipe) {
-		pipe->bufs = kzalloc(sizeof(struct pipe_buffer) * PIPE_DEF_BUFFERS, GFP_KERNEL);
+		pipe->bufs = kzalloc(sizeof(struct pipe_buffer) * PIPE_DEF_BUFFERS, GFP_KERNEL | __GFP_ACCOUNT);
 		if (pipe->bufs) {
 			init_waitqueue_head(&pipe->wait);
 			pipe->r_counter = pipe->w_counter = 1;
@@ -971,7 +971,7 @@ static long pipe_set_size(struct pipe_inode_info *pipe, unsigned long nr_pages)
 	if (nr_pages < pipe->nrbufs)
 		return -EBUSY;
 
-	bufs = kcalloc(nr_pages, sizeof(*bufs), GFP_KERNEL | __GFP_NOWARN);
+	bufs = kcalloc(nr_pages, sizeof(*bufs), GFP_KERNEL | __GFP_NOWARN | __GFP_ACCOUNT);
 	if (unlikely(!bufs))
 		return -ENOMEM;
 
-- 
Michal Hocko
SUSE Labs
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