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Commit 5a5f0792 authored by David S. Miller's avatar David S. Miller
Browse files

Merge branch 'pskb_extract' 

Sowmini Varadhan says:

====================
pskb_extract() helper function.

This patchset follows up on the discussion in
 https://www.mail-archive.com/netdev@vger.kernel.org/msg105090.html



For RDS-TCP, we have to deal with the full gamut of
nonlinear sk_buffs, including all the frag_list variants.
Also, the parent skb has to remain unchanged, while the clone
is queued for Rx on the PF_RDS socket.

Patch 1 of this patchset adds a pskb_extract() function that
does all this without the redundant memcpy's in pskb_expand_head()
and __pskb_pull_tail().

v2: Marcelo Leitner review comments
====================

Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parents 557fc4a0 947d2756

include/linux/skbuff.h

+2 −0
Original line number Diff line number Diff line
@@ -2986,6 +2986,8 @@ struct sk_buff *skb_vlan_untag(struct sk_buff *skb); 
int skb_ensure_writable(struct sk_buff *skb, int write_len);

int skb_vlan_pop(struct sk_buff *skb);

int skb_vlan_push(struct sk_buff *skb, __be16 vlan_proto, u16 vlan_tci);

struct sk_buff *pskb_extract(struct sk_buff *skb, int off, int to_copy,

			     gfp_t gfp);



static inline int memcpy_from_msg(void *data, struct msghdr *msg, int len)

{

net/core/skbuff.c

+242 −0
Original line number Diff line number Diff line
@@ -4622,3 +4622,245 @@ struct sk_buff *alloc_skb_with_frags(unsigned long header_len, 
	return NULL;

}

EXPORT_SYMBOL(alloc_skb_with_frags);



/* carve out the first off bytes from skb when off < headlen */

static int pskb_carve_inside_header(struct sk_buff *skb, const u32 off,

				    const int headlen, gfp_t gfp_mask)

{

	int i;

	int size = skb_end_offset(skb);

	int new_hlen = headlen - off;

	u8 *data;

	int doff = 0;



	size = SKB_DATA_ALIGN(size);



	if (skb_pfmemalloc(skb))

		gfp_mask |= __GFP_MEMALLOC;

	data = kmalloc_reserve(size +

			       SKB_DATA_ALIGN(sizeof(struct skb_shared_info)),

			       gfp_mask, NUMA_NO_NODE, NULL);

	if (!data)

		return -ENOMEM;



	size = SKB_WITH_OVERHEAD(ksize(data));



	/* Copy real data, and all frags */

	skb_copy_from_linear_data_offset(skb, off, data, new_hlen);

	skb->len -= off;



	memcpy((struct skb_shared_info *)(data + size),

	       skb_shinfo(skb),

	       offsetof(struct skb_shared_info,

			frags[skb_shinfo(skb)->nr_frags]));

	if (skb_cloned(skb)) {

		/* drop the old head gracefully */

		if (skb_orphan_frags(skb, gfp_mask)) {

			kfree(data);

			return -ENOMEM;

		}

		for (i = 0; i < skb_shinfo(skb)->nr_frags; i++)

			skb_frag_ref(skb, i);

		if (skb_has_frag_list(skb))

			skb_clone_fraglist(skb);

		skb_release_data(skb);

	} else {

		/* we can reuse existing recount- all we did was

		 * relocate values

		 */

		skb_free_head(skb);

	}



	doff = (data - skb->head);

	skb->head = data;

	skb->data = data;

	skb->head_frag = 0;

#ifdef NET_SKBUFF_DATA_USES_OFFSET

	skb->end = size;

	doff = 0;

#else

	skb->end = skb->head + size;

#endif

	skb_set_tail_pointer(skb, skb_headlen(skb));

	skb_headers_offset_update(skb, 0);

	skb->cloned = 0;

	skb->hdr_len = 0;

	skb->nohdr = 0;

	atomic_set(&skb_shinfo(skb)->dataref, 1);



	return 0;

}



static int pskb_carve(struct sk_buff *skb, const u32 off, gfp_t gfp);



/* carve out the first eat bytes from skb's frag_list. May recurse into

 * pskb_carve()

 */

static int pskb_carve_frag_list(struct sk_buff *skb,

				struct skb_shared_info *shinfo, int eat,

				gfp_t gfp_mask)

{

	struct sk_buff *list = shinfo->frag_list;

	struct sk_buff *clone = NULL;

	struct sk_buff *insp = NULL;



	do {

		if (!list) {

			pr_err("Not enough bytes to eat. Want %d\n", eat);

			return -EFAULT;

		}

		if (list->len <= eat) {

			/* Eaten as whole. */

			eat -= list->len;

			list = list->next;

			insp = list;

		} else {

			/* Eaten partially. */

			if (skb_shared(list)) {

				clone = skb_clone(list, gfp_mask);

				if (!clone)

					return -ENOMEM;

				insp = list->next;

				list = clone;

			} else {

				/* This may be pulled without problems. */

				insp = list;

			}

			if (pskb_carve(list, eat, gfp_mask) < 0) {

				kfree_skb(clone);

				return -ENOMEM;

			}

			break;

		}

	} while (eat);



	/* Free pulled out fragments. */

	while ((list = shinfo->frag_list) != insp) {

		shinfo->frag_list = list->next;

		kfree_skb(list);

	}

	/* And insert new clone at head. */

	if (clone) {

		clone->next = list;

		shinfo->frag_list = clone;

	}

	return 0;

}



/* carve off first len bytes from skb. Split line (off) is in the

 * non-linear part of skb

 */

static int pskb_carve_inside_nonlinear(struct sk_buff *skb, const u32 off,

				       int pos, gfp_t gfp_mask)

{

	int i, k = 0;

	int size = skb_end_offset(skb);

	u8 *data;

	const int nfrags = skb_shinfo(skb)->nr_frags;

	struct skb_shared_info *shinfo;

	int doff = 0;



	size = SKB_DATA_ALIGN(size);



	if (skb_pfmemalloc(skb))

		gfp_mask |= __GFP_MEMALLOC;

	data = kmalloc_reserve(size +

			       SKB_DATA_ALIGN(sizeof(struct skb_shared_info)),

			       gfp_mask, NUMA_NO_NODE, NULL);

	if (!data)

		return -ENOMEM;



	size = SKB_WITH_OVERHEAD(ksize(data));



	memcpy((struct skb_shared_info *)(data + size),

	       skb_shinfo(skb), offsetof(struct skb_shared_info,

					 frags[skb_shinfo(skb)->nr_frags]));

	if (skb_orphan_frags(skb, gfp_mask)) {

		kfree(data);

		return -ENOMEM;

	}

	shinfo = (struct skb_shared_info *)(data + size);

	for (i = 0; i < nfrags; i++) {

		int fsize = skb_frag_size(&skb_shinfo(skb)->frags[i]);



		if (pos + fsize > off) {

			shinfo->frags[k] = skb_shinfo(skb)->frags[i];



			if (pos < off) {

				/* Split frag.

				 * We have two variants in this case:

				 * 1. Move all the frag to the second

				 *    part, if it is possible. F.e.

				 *    this approach is mandatory for TUX,

				 *    where splitting is expensive.

				 * 2. Split is accurately. We make this.

				 */

				shinfo->frags[0].page_offset += off - pos;

				skb_frag_size_sub(&shinfo->frags[0], off - pos);

			}

			skb_frag_ref(skb, i);

			k++;

		}

		pos += fsize;

	}

	shinfo->nr_frags = k;

	if (skb_has_frag_list(skb))

		skb_clone_fraglist(skb);



	if (k == 0) {

		/* split line is in frag list */

		pskb_carve_frag_list(skb, shinfo, off - pos, gfp_mask);

	}

	skb_release_data(skb);



	doff = (data - skb->head);

	skb->head = data;

	skb->head_frag = 0;

	skb->data = data;

#ifdef NET_SKBUFF_DATA_USES_OFFSET

	skb->end = size;

	doff = 0;

#else

	skb->end = skb->head + size;

#endif

	skb_reset_tail_pointer(skb);

	skb_headers_offset_update(skb, 0);

	skb->cloned   = 0;

	skb->hdr_len  = 0;

	skb->nohdr    = 0;

	skb->len -= off;

	skb->data_len = skb->len;

	atomic_set(&skb_shinfo(skb)->dataref, 1);

	return 0;

}



/* remove len bytes from the beginning of the skb */

static int pskb_carve(struct sk_buff *skb, const u32 len, gfp_t gfp)

{

	int headlen = skb_headlen(skb);



	if (len < headlen)

		return pskb_carve_inside_header(skb, len, headlen, gfp);

	else

		return pskb_carve_inside_nonlinear(skb, len, headlen, gfp);

}



/* Extract to_copy bytes starting at off from skb, and return this in

 * a new skb

 */

struct sk_buff *pskb_extract(struct sk_buff *skb, int off,

			     int to_copy, gfp_t gfp)

{

	struct sk_buff  *clone = skb_clone(skb, gfp);



	if (!clone)

		return NULL;



	if (pskb_carve(clone, off, gfp) < 0 ||

	    pskb_trim(clone, to_copy)) {

		kfree_skb(clone);

		return NULL;

	}

	return clone;

}

EXPORT_SYMBOL(pskb_extract);

net/rds/tcp_recv.c

+3 −11
Original line number Diff line number Diff line
@@ -207,22 +207,14 @@ static int rds_tcp_data_recv(read_descriptor_t *desc, struct sk_buff *skb, 
		}



		if (left && tc->t_tinc_data_rem) {

			clone = skb_clone(skb, arg->gfp);

			to_copy = min(tc->t_tinc_data_rem, left);



			clone = pskb_extract(skb, offset, to_copy, arg->gfp);

			if (!clone) {

				desc->error = -ENOMEM;

				goto out;

			}



			to_copy = min(tc->t_tinc_data_rem, left);

			if (!pskb_pull(clone, offset) ||

			    pskb_trim(clone, to_copy)) {

				pr_warn("rds_tcp_data_recv: pull/trim failed "

					"left %zu data_rem %zu skb_len %d\n",

					left, tc->t_tinc_data_rem, skb->len);

				kfree_skb(clone);

				desc->error = -ENOMEM;

				goto out;

			}

			skb_queue_tail(&tinc->ti_skb_list, clone);



			rdsdebug("skb %p data %p len %d off %u to_copy %zu -> "