lkml.org 
[lkml]   [2014]   [Jul]   [17]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH net 3/4] xen-netback: Fix releasing header slot on error path
    Date
    This patch makes this function aware that the first frag and the header might
    share the same ring slot. That could happen if the first slot is bigger than
    MAX_SKB_LEN. Due to this the error path might release that slot twice or never,
    depending on the error scenario.
    xenvif_idx_release is also removed from xenvif_idx_unmap, and called separately.

    Signed-off-by: Zoltan Kiss <zoltan.kiss@citrix.com>
    Reported-by: Armin Zentai <armin.zentai@ezit.hu>
    Cc: netdev@vger.kernel.org
    Cc: linux-kernel@vger.kernel.org
    Cc: xen-devel@lists.xenproject.org
    ---
    diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c
    index e9ffb05..938d5a9 100644
    --- a/drivers/net/xen-netback/netback.c
    +++ b/drivers/net/xen-netback/netback.c
    @@ -1039,6 +1039,8 @@ static int xenvif_tx_check_gop(struct xenvif_queue *queue,
    */
    struct skb_shared_info *first_shinfo = NULL;
    int nr_frags = shinfo->nr_frags;
    + const bool sharedslot = nr_frags &&
    + frag_get_pending_idx(&shinfo->frags[0]) == pending_idx;
    int i, err;

    /* Check status of header. */
    @@ -1051,7 +1053,10 @@ static int xenvif_tx_check_gop(struct xenvif_queue *queue,
    (*gopp_copy)->status,
    pending_idx,
    (*gopp_copy)->source.u.ref);
    - xenvif_idx_release(queue, pending_idx, XEN_NETIF_RSP_ERROR);
    + /* The first frag might still have this slot mapped */
    + if (!sharedslot)
    + xenvif_idx_release(queue, pending_idx,
    + XEN_NETIF_RSP_ERROR);
    }

    check_frags:
    @@ -1068,8 +1073,19 @@ check_frags:
    pending_idx,
    gop_map->handle);
    /* Had a previous error? Invalidate this fragment. */
    - if (unlikely(err))
    + if (unlikely(err)) {
    xenvif_idx_unmap(queue, pending_idx);
    + /* If the mapping of the first frag was OK, but
    + * the header's copy failed, and they are
    + * sharing a slot, send an error
    + */
    + if (i == 0 && sharedslot)
    + xenvif_idx_release(queue, pending_idx,
    + XEN_NETIF_RSP_ERROR);
    + else
    + xenvif_idx_release(queue, pending_idx,
    + XEN_NETIF_RSP_OKAY);
    + }
    continue;
    }

    @@ -1081,15 +1097,27 @@ check_frags:
    gop_map->status,
    pending_idx,
    gop_map->ref);
    +
    xenvif_idx_release(queue, pending_idx, XEN_NETIF_RSP_ERROR);

    /* Not the first error? Preceding frags already invalidated. */
    if (err)
    continue;
    - /* First error: invalidate preceding fragments. */
    +
    + /* First error: if the header haven't shared a slot with the
    + * first frag, release it as well.
    + */
    + if (!sharedslot)
    + xenvif_idx_release(queue,
    + XENVIF_TX_CB(skb)->pending_idx,
    + XEN_NETIF_RSP_OKAY);
    +
    + /* Invalidate preceding fragments of this skb. */
    for (j = 0; j < i; j++) {
    pending_idx = frag_get_pending_idx(&shinfo->frags[j]);
    xenvif_idx_unmap(queue, pending_idx);
    + xenvif_idx_release(queue, pending_idx,
    + XEN_NETIF_RSP_OKAY);
    }

    /* And if we found the error while checking the frag_list, unmap
    @@ -1099,6 +1127,8 @@ check_frags:
    for (j = 0; j < first_shinfo->nr_frags; j++) {
    pending_idx = frag_get_pending_idx(&first_shinfo->frags[j]);
    xenvif_idx_unmap(queue, pending_idx);
    + xenvif_idx_release(queue, pending_idx,
    + XEN_NETIF_RSP_OKAY);
    }
    }

    @@ -1830,8 +1860,6 @@ void xenvif_idx_unmap(struct xenvif_queue *queue, u16 pending_idx)
    tx_unmap_op.status);
    BUG();
    }
    -
    - xenvif_idx_release(queue, pending_idx, XEN_NETIF_RSP_OKAY);
    }

    static inline int rx_work_todo(struct xenvif_queue *queue)

    \
     
     \ /
      Last update: 2014-07-17 21:41    [W:2.262 / U:0.024 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site