Re: [PATCH net-next v2 6/6] net: dsa: factor skb freeing on xmit
From: Florian Fainelli <f.fainelli@gmail.com>
Date: 2017-05-30 20:59:09
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lkml
On 05/30/2017 11:33 AM, Vivien Didelot wrote:
The taggers are currently responsible to free the original SKB if they made a copy of it, or in case of error. This patch simplifies this by freeing the original SKB in the dsa_slave_xmit caller, but only if an error (NULL) is returned.
Is not it a clearer contract if the tagging protocol must always free the original SKB, whether it succeeded in creating a new one or not?
quoted hunk ↗ jump to hunk
It is still the responsibility of the tagger to free the original SKB if it returned a copy of it. At the same time, fix the checkpatch NULL comparison check: CHECK: Comparison to NULL could be written "!nskb" #208: FILE: net/dsa/tag_trailer.c:35: + if (nskb == NULL) Signed-off-by: Vivien Didelot <redacted> --- net/dsa/slave.c | 8 ++++++-- net/dsa/tag_brcm.c | 6 +----- net/dsa/tag_dsa.c | 8 ++------ net/dsa/tag_edsa.c | 8 ++------ net/dsa/tag_lan9303.c | 5 +---- net/dsa/tag_mtk.c | 6 +----- net/dsa/tag_qca.c | 6 +----- net/dsa/tag_trailer.c | 4 +--- 8 files changed, 15 insertions(+), 36 deletions(-)diff --git a/net/dsa/slave.c b/net/dsa/slave.c index 887e26695519..4473aec9dcda 100644 --- a/net/dsa/slave.c +++ b/net/dsa/slave.c@@ -362,10 +362,14 @@ static netdev_tx_t dsa_slave_xmit(struct sk_buff *skb, struct net_device *dev) dev->stats.tx_packets++; dev->stats.tx_bytes += skb->len; - /* Transmit function may have to reallocate the original SKB */ + /* Transmit function may have to reallocate the original SKB, + * in which case it must have freed it. Only free it here on error. + */ nskb = p->xmit(skb, dev); - if (!nskb) + if (!nskb) { + kfree_skb(skb); return NETDEV_TX_OK; + } /* SKB for netpoll still need to be mangled with the protocol-specific * tag to be successfully transmitteddiff --git a/net/dsa/tag_brcm.c b/net/dsa/tag_brcm.c index 10fa4c0ca46b..5db6bcfde025 100644 --- a/net/dsa/tag_brcm.c +++ b/net/dsa/tag_brcm.c@@ -65,7 +65,7 @@ static struct sk_buff *brcm_tag_xmit(struct sk_buff *skb, struct net_device *dev u8 *brcm_tag; if (skb_cow_head(skb, BRCM_TAG_LEN) < 0) - goto out_free; + return NULL; skb_push(skb, BRCM_TAG_LEN);@@ -86,10 +86,6 @@ static struct sk_buff *brcm_tag_xmit(struct sk_buff *skb, struct net_device *dev brcm_tag[3] = (1 << p->dp->index) & BRCM_IG_DSTMAP1_MASK; return skb; - -out_free: - kfree_skb(skb); - return NULL; } static struct sk_buff *brcm_tag_rcv(struct sk_buff *skb, struct net_device *dev)diff --git a/net/dsa/tag_dsa.c b/net/dsa/tag_dsa.c index 9f5fecaa4a93..6837ca9160a8 100644 --- a/net/dsa/tag_dsa.c +++ b/net/dsa/tag_dsa.c@@ -28,7 +28,7 @@ static struct sk_buff *dsa_xmit(struct sk_buff *skb, struct net_device *dev) */ if (skb->protocol == htons(ETH_P_8021Q)) { if (skb_cow_head(skb, 0) < 0) - goto out_free; + return NULL; /* * Construct tagged FROM_CPU DSA tag from 802.1q tag.@@ -46,7 +46,7 @@ static struct sk_buff *dsa_xmit(struct sk_buff *skb, struct net_device *dev) } } else { if (skb_cow_head(skb, DSA_HLEN) < 0) - goto out_free; + return NULL; skb_push(skb, DSA_HLEN); memmove(skb->data, skb->data + DSA_HLEN, 2 * ETH_ALEN);@@ -62,10 +62,6 @@ static struct sk_buff *dsa_xmit(struct sk_buff *skb, struct net_device *dev) } return skb; - -out_free: - kfree_skb(skb); - return NULL; } static struct sk_buff *dsa_rcv(struct sk_buff *skb, struct net_device *dev)diff --git a/net/dsa/tag_edsa.c b/net/dsa/tag_edsa.c index a9a06e19abeb..96ddc90472a2 100644 --- a/net/dsa/tag_edsa.c +++ b/net/dsa/tag_edsa.c@@ -30,7 +30,7 @@ static struct sk_buff *edsa_xmit(struct sk_buff *skb, struct net_device *dev) */ if (skb->protocol == htons(ETH_P_8021Q)) { if (skb_cow_head(skb, DSA_HLEN) < 0) - goto out_free; + return NULL; skb_push(skb, DSA_HLEN); memmove(skb->data, skb->data + DSA_HLEN, 2 * ETH_ALEN);@@ -55,7 +55,7 @@ static struct sk_buff *edsa_xmit(struct sk_buff *skb, struct net_device *dev) } } else { if (skb_cow_head(skb, EDSA_HLEN) < 0) - goto out_free; + return NULL; skb_push(skb, EDSA_HLEN); memmove(skb->data, skb->data + EDSA_HLEN, 2 * ETH_ALEN);@@ -75,10 +75,6 @@ static struct sk_buff *edsa_xmit(struct sk_buff *skb, struct net_device *dev) } return skb; - -out_free: - kfree_skb(skb); - return NULL; } static struct sk_buff *edsa_rcv(struct sk_buff *skb, struct net_device *dev)diff --git a/net/dsa/tag_lan9303.c b/net/dsa/tag_lan9303.c index 82e150486497..e33348101e8f 100644 --- a/net/dsa/tag_lan9303.c +++ b/net/dsa/tag_lan9303.c@@ -52,7 +52,7 @@ static struct sk_buff *lan9303_xmit(struct sk_buff *skb, struct net_device *dev) if (skb_cow_head(skb, LAN9303_TAG_LEN) < 0) { dev_dbg(&dev->dev, "Cannot make room for the special tag. Dropping packet\n"); - goto out_free; + return NULL; } /* provide 'LAN9303_TAG_LEN' bytes additional space */@@ -66,9 +66,6 @@ static struct sk_buff *lan9303_xmit(struct sk_buff *skb, struct net_device *dev) lan9303_tag[1] = htons(p->dp->index | BIT(4)); return skb; -out_free: - kfree_skb(skb); - return NULL; } static struct sk_buff *lan9303_rcv(struct sk_buff *skb, struct net_device *dev)diff --git a/net/dsa/tag_mtk.c b/net/dsa/tag_mtk.c index 327dd7b596df..ee62ae5f03e1 100644 --- a/net/dsa/tag_mtk.c +++ b/net/dsa/tag_mtk.c@@ -27,7 +27,7 @@ static struct sk_buff *mtk_tag_xmit(struct sk_buff *skb, u8 *mtk_tag; if (skb_cow_head(skb, MTK_HDR_LEN) < 0) - goto out_free; + return NULL; skb_push(skb, MTK_HDR_LEN);@@ -41,10 +41,6 @@ static struct sk_buff *mtk_tag_xmit(struct sk_buff *skb, mtk_tag[3] = 0; return skb; - -out_free: - kfree_skb(skb); - return NULL; } static struct sk_buff *mtk_tag_rcv(struct sk_buff *skb, struct net_device *dev)diff --git a/net/dsa/tag_qca.c b/net/dsa/tag_qca.c index 8080ad8f2abb..4d3bc2920477 100644 --- a/net/dsa/tag_qca.c +++ b/net/dsa/tag_qca.c@@ -45,7 +45,7 @@ static struct sk_buff *qca_tag_xmit(struct sk_buff *skb, struct net_device *dev) dev->stats.tx_bytes += skb->len; if (skb_cow_head(skb, 0) < 0) - goto out_free; + return NULL; skb_push(skb, QCA_HDR_LEN);@@ -60,10 +60,6 @@ static struct sk_buff *qca_tag_xmit(struct sk_buff *skb, struct net_device *dev) *phdr = htons(hdr); return skb; - -out_free: - kfree_skb(skb); - return NULL; } static struct sk_buff *qca_tag_rcv(struct sk_buff *skb, struct net_device *dev)diff --git a/net/dsa/tag_trailer.c b/net/dsa/tag_trailer.c index 7422b1329712..8c9a7f5ecc66 100644 --- a/net/dsa/tag_trailer.c +++ b/net/dsa/tag_trailer.c@@ -32,10 +32,8 @@ static struct sk_buff *trailer_xmit(struct sk_buff *skb, struct net_device *dev) padlen = 60 - skb->len; nskb = alloc_skb(NET_IP_ALIGN + skb->len + padlen + 4, GFP_ATOMIC); - if (nskb == NULL) { - kfree_skb(skb); + if (!nskb) return NULL; - } skb_reserve(nskb, NET_IP_ALIGN); skb_reset_mac_header(nskb);
-- Florian