From 8644772637deb121f7ac2df690cbf83fa63d3b70 Mon Sep 17 00:00:00 2001 From: Alexander Duyck Date: Fri, 15 Feb 2019 14:44:12 -0800 Subject: [PATCH 1/2] mm: Use fixed constant in page_frag_alloc instead of size + 1 This patch replaces the size + 1 value introduced with the recent fix for 1 byte allocs with a constant value. The idea here is to reduce code overhead as the previous logic would have to read size into a register, then increment it, and write it back to whatever field was being used. By using a constant we can avoid those memory reads and arithmetic operations in favor of just encoding the maximum value into the operation itself. Fixes: 2c2ade81741c ("mm: page_alloc: fix ref bias in page_frag_alloc() for 1-byte allocs") Signed-off-by: Alexander Duyck Signed-off-by: David S. Miller --- mm/page_alloc.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 46285d28e43b..7f79b78bc829 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -4675,11 +4675,11 @@ refill: /* Even if we own the page, we do not use atomic_set(). * This would break get_page_unless_zero() users. */ - page_ref_add(page, size); + page_ref_add(page, PAGE_FRAG_CACHE_MAX_SIZE); /* reset page count bias and offset to start of new frag */ nc->pfmemalloc = page_is_pfmemalloc(page); - nc->pagecnt_bias = size + 1; + nc->pagecnt_bias = PAGE_FRAG_CACHE_MAX_SIZE + 1; nc->offset = size; } @@ -4695,10 +4695,10 @@ refill: size = nc->size; #endif /* OK, page count is 0, we can safely set it */ - set_page_count(page, size + 1); + set_page_count(page, PAGE_FRAG_CACHE_MAX_SIZE + 1); /* reset page count bias and offset to start of new frag */ - nc->pagecnt_bias = size + 1; + nc->pagecnt_bias = PAGE_FRAG_CACHE_MAX_SIZE + 1; offset = size - fragsz; } From 3bed3cc4156eedf652b4df72bdb35d4f1a2a739d Mon Sep 17 00:00:00 2001 From: Alexander Duyck Date: Fri, 15 Feb 2019 14:44:18 -0800 Subject: [PATCH 2/2] net: Do not allocate page fragments that are not skb aligned This patch addresses the fact that there are drivers, specifically tun, that will call into the network page fragment allocators with buffer sizes that are not cache aligned. Doing this could result in data alignment and DMA performance issues as these fragment pools are also shared with the skb allocator and any other devices that will use napi_alloc_frags or netdev_alloc_frags. Fixes: ffde7328a36d ("net: Split netdev_alloc_frag into __alloc_page_frag and add __napi_alloc_frag") Reported-by: Jann Horn Signed-off-by: Alexander Duyck Signed-off-by: David S. Miller --- net/core/skbuff.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/net/core/skbuff.c b/net/core/skbuff.c index 26d848484912..2415d9cb9b89 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -356,6 +356,8 @@ static void *__netdev_alloc_frag(unsigned int fragsz, gfp_t gfp_mask) */ void *netdev_alloc_frag(unsigned int fragsz) { + fragsz = SKB_DATA_ALIGN(fragsz); + return __netdev_alloc_frag(fragsz, GFP_ATOMIC); } EXPORT_SYMBOL(netdev_alloc_frag); @@ -369,6 +371,8 @@ static void *__napi_alloc_frag(unsigned int fragsz, gfp_t gfp_mask) void *napi_alloc_frag(unsigned int fragsz) { + fragsz = SKB_DATA_ALIGN(fragsz); + return __napi_alloc_frag(fragsz, GFP_ATOMIC); } EXPORT_SYMBOL(napi_alloc_frag);