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eth: fbnic: remove the debugging trick of super high page bias

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Alex added page bias of LONG_MAX, which is admittedly quite
a clever way of catching overflows of the pp ref count.
The page pool code was "optimized" to leave the ref at 1
for freed pages so it can't catch basic bugs by itself any more.
(Something we should probably address under DEBUG_NET...)

Unfortunately for fbnic since commit f7dc3248dc ("skbuff: Optimization
of SKB coalescing for page pool") core _may_ actually take two extra
pp refcounts, if one of them is returned before driver gives up the bias
the ret < 0 check in page_pool_unref_netmem() will trigger.

While at it add a FBNIC_ to the name of the driver constant.

Fixes: 0cb4c0a137 ("eth: fbnic: Implement Rx queue alloc/start/stop/free")
Link: https://patch.msgid.link/20250801170754.2439577-1-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Jakub Kicinski 2025-08-01 10:07:54 -07:00
parent e88fbc30dd
commit e407fceeaf
2 changed files with 4 additions and 6 deletions
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4
drivers/net/ethernet/meta/fbnic/fbnic_txrx.c
View File

@ -661,8 +661,8 @@ static void fbnic_page_pool_init(struct fbnic_ring *ring, unsigned int idx,
{
struct fbnic_rx_buf *rx_buf = &ring->rx_buf[idx];
page_pool_fragment_page(page, PAGECNT_BIAS_MAX);
rx_buf->pagecnt_bias = PAGECNT_BIAS_MAX;
page_pool_fragment_page(page, FBNIC_PAGECNT_BIAS_MAX);
rx_buf->pagecnt_bias = FBNIC_PAGECNT_BIAS_MAX;
rx_buf->page = page;
}

6
drivers/net/ethernet/meta/fbnic/fbnic_txrx.h
View File

@ -91,10 +91,8 @@ struct fbnic_queue_stats {
struct u64_stats_sync syncp;
};
/* Pagecnt bias is long max to reserve the last bit to catch overflow
* cases where if we overcharge the bias it will flip over to be negative.
*/
#define PAGECNT_BIAS_MAX LONG_MAX
#define FBNIC_PAGECNT_BIAS_MAX PAGE_SIZE
struct fbnic_rx_buf {
struct page *page;
long pagecnt_bias;