Messages in this thread | | | Date | Mon, 7 Dec 2020 17:28:31 +0100 | From | Marco Elver <> | Subject | Re: WARNING in sk_stream_kill_queues (5) |
| |
On Thu, Dec 03, 2020 at 07:01PM +0100, Eric Dumazet wrote: > On 12/3/20 6:41 PM, Marco Elver wrote: > > > One more experiment -- simply adding > > > > --- a/net/core/skbuff.c > > +++ b/net/core/skbuff.c > > @@ -207,7 +207,21 @@ struct sk_buff *__alloc_skb(unsigned int size, gfp_t gfp_mask, > > */ > > size = SKB_DATA_ALIGN(size); > > size += SKB_DATA_ALIGN(sizeof(struct skb_shared_info)); > > + size = 1 << kmalloc_index(size); /* HACK */ > > data = kmalloc_reserve(size, gfp_mask, node, &pfmemalloc); > > > > > > also got rid of the warnings. Something must be off with some value that > > is computed in terms of ksize(). If not, I don't have any explanation > > for why the above hides the problem. > > Maybe the implementations of various macros (SKB_DATA_ALIGN and friends) > hae some kind of assumptions, I will double check this.
Some more data; removing all uses of ksize() fixes the warnings:
| --- a/net/core/skbuff.c | +++ b/net/core/skbuff.c | @@ -214,7 +214,7 @@ struct sk_buff *__alloc_skb(unsigned int size, gfp_t gfp_mask, | * Put skb_shared_info exactly at the end of allocated zone, | * to allow max possible filling before reallocation. | */ | - size = SKB_WITH_OVERHEAD(ksize(data)); | + size = SKB_WITH_OVERHEAD(size); | prefetchw(data + size); | | /* | @@ -1628,7 +1628,7 @@ int pskb_expand_head(struct sk_buff *skb, int nhead, int ntail, | gfp_mask, NUMA_NO_NODE, NULL); | if (!data) | goto nodata; | - size = SKB_WITH_OVERHEAD(ksize(data)); | + size = SKB_WITH_OVERHEAD(size + SKB_DATA_ALIGN(sizeof(struct skb_shared_info))); ^^ Reverting *only* this to 'ksize(data)' triggers the warning. | /* Copy only real data... and, alas, header. This should be | * optimized for the cases when header is void. | @@ -5901,7 +5901,7 @@ static int pskb_carve_inside_header(struct sk_buff *skb, const u32 off, | if (!data) | return -ENOMEM; | | - size = SKB_WITH_OVERHEAD(ksize(data)); | + size = SKB_WITH_OVERHEAD(size + SKB_DATA_ALIGN(sizeof(struct skb_shared_info))); | | /* Copy real data, and all frags */ | skb_copy_from_linear_data_offset(skb, off, data, new_hlen); | @@ -6025,7 +6025,7 @@ static int pskb_carve_inside_nonlinear(struct sk_buff *skb, const u32 off, | if (!data) | return -ENOMEM; | | - size = SKB_WITH_OVERHEAD(ksize(data)); | + size = SKB_WITH_OVERHEAD(size + SKB_DATA_ALIGN(sizeof(struct skb_shared_info))); | | memcpy((struct skb_shared_info *)(data + size), | skb_shinfo(skb), offsetof(struct skb_shared_info, frags[0]));
Conversely, only doing this also fixes the warnings:
| --- a/net/core/skbuff.c | +++ b/net/core/skbuff.c | @@ -1628,7 +1628,7 @@ int pskb_expand_head(struct sk_buff *skb, int nhead, int ntail, | gfp_mask, NUMA_NO_NODE, NULL); | if (!data) | goto nodata; | - size = SKB_WITH_OVERHEAD(ksize(data)); | + size = SKB_WITH_OVERHEAD(size + SKB_DATA_ALIGN(sizeof(struct skb_shared_info))); | | /* Copy only real data... and, alas, header. This should be | * optimized for the cases when header is void.
But not sure if any of this is helpful, since in the end what we want is to make a bunch of subtractions reach precisely 0, and any deviation somewhere might, by chance, achieve that.
Thanks, -- Marco
| |