From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D5122BE49 for ; Fri, 14 Nov 2025 11:17:20 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763119040; cv=none; b=nRXf4RJcCc04NXcX7sBxyJOUcDBqA0B01kNnmN5FzLSCHTAcG+5Zd12EExC2cllN1pPRL0DeyzOqPN6Ff7cX6EEace1x2us+qNl/J5p9TMHC56xqtIroiyyI98yNAIrhTpAhq8SKKYfcsLeRdbpRx31b8bux/Os8PhqKvAyH3b4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763119040; c=relaxed/simple; bh=xkINaQL7eF96dscoLugPyzbmfWscrdmgdO7KVx5Chkg=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=mZCS3jI8F/PZwoVSFecTNte4hzcSvAb2nwI71G7iwOLmy+/5gRLNkuNrJCOtGaqUWmS+l8+kEYmnxowBYG9PqitZzXhYKvgoha/dalUPDrf16sDI3mBAzOjXQbIh8lrDz7+CCkM9McpUHNd3LKJ/StbJOqzxnklE2mKDIsK5xtA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=KdVAhrFy; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="KdVAhrFy" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 26091C16AAE; Fri, 14 Nov 2025 11:17:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1763119040; bh=xkINaQL7eF96dscoLugPyzbmfWscrdmgdO7KVx5Chkg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=KdVAhrFyz5JCZrIdBr6mtuswzBmZi0KHfTyrt6N7+M8UWg0oVp6NaGC66355pqwf/ hqQffIn0Psz+/ByWJAn3OxVfkjHBdHX6rfxo1y8v4PVJzNB+R/YvEO6Hjd/WhBQR/k 51JnHJ6+ZYW0Nw6JpLf7kT/1yphE7PldD9CwW367QFPhpg51hAWCMBYqYFafMPvIIn eK9Cd7YVHAgK1q5aEeaVEHrUqyUaQ/UYAh1D4WAnolOZ5VDD/atJZWWOKzHxTohnaj +qEAwXEu5Lp8N3FnqCcvf03N44E9Qf57wo2/Gd1nBMsetX2Pafcw433sCbuQWIQsG1 Tmyj93dvat1JA== From: Puranjay Mohan To: bpf@vger.kernel.org Cc: Puranjay Mohan , Puranjay Mohan , Alexei Starovoitov , Andrii Nakryiko , Daniel Borkmann , Martin KaFai Lau , Eduard Zingerman , Kumar Kartikeya Dwivedi , kernel-team@meta.com Subject: [PATCH bpf-next v2 2/4] bpf: arena: use kmalloc_nolock() in place of kvcalloc() Date: Fri, 14 Nov 2025 11:16:57 +0000 Message-ID: <20251114111700.43292-3-puranjay@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20251114111700.43292-1-puranjay@kernel.org> References: <20251114111700.43292-1-puranjay@kernel.org> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit To make arena_alloc_pages() safe to be called from any context, replace kvcalloc() with kmalloc_nolock() so as it doesn't sleep or take any locks. kmalloc_nolock() returns NULL for allocations larger than KMALLOC_MAX_CACHE_SIZE, which is (PAGE_SIZE * 2) = 8KB on systems with 4KB pages. So, round down the allocation done by kmalloc_nolock to 1024 * 8 and reuse the array in a loop. Signed-off-by: Puranjay Mohan --- kernel/bpf/arena.c | 76 +++++++++++++++++++++++++++++++--------------- 1 file changed, 52 insertions(+), 24 deletions(-) diff --git a/kernel/bpf/arena.c b/kernel/bpf/arena.c index 48b8ffba3c88..7fa6e40ab3fc 100644 --- a/kernel/bpf/arena.c +++ b/kernel/bpf/arena.c @@ -43,6 +43,8 @@ #define GUARD_SZ round_up(1ull << sizeof_field(struct bpf_insn, off) * 8, PAGE_SIZE << 1) #define KERN_VM_SZ (SZ_4G + GUARD_SZ) +static void arena_free_pages(struct bpf_arena *arena, long uaddr, long page_cnt); + struct bpf_arena { struct bpf_map map; u64 user_vm_start; @@ -491,7 +493,10 @@ static long arena_alloc_pages(struct bpf_arena *arena, long uaddr, long page_cnt /* user_vm_end/start are fixed before bpf prog runs */ long page_cnt_max = (arena->user_vm_end - arena->user_vm_start) >> PAGE_SHIFT; u64 kern_vm_start = bpf_arena_get_kern_vm_start(arena); + struct apply_range_data data; struct page **pages = NULL; + long remaining, mapped = 0; + long alloc_pages; long pgoff = 0; u32 uaddr32; int ret, i; @@ -508,12 +513,16 @@ static long arena_alloc_pages(struct bpf_arena *arena, long uaddr, long page_cnt return 0; } - /* zeroing is needed, since alloc_pages_bulk() only fills in non-zero entries */ - pages = kvcalloc(page_cnt, sizeof(struct page *), GFP_KERNEL); + /* + * Cap allocation size to KMALLOC_MAX_CACHE_SIZE so kmalloc_nolock() can succeed. + */ + alloc_pages = min(page_cnt, KMALLOC_MAX_CACHE_SIZE / sizeof(struct page *)); + pages = kmalloc_nolock(alloc_pages * sizeof(struct page *), 0, NUMA_NO_NODE); if (!pages) return 0; + data.pages = pages; - guard(mutex)(&arena->lock); + mutex_lock(&arena->lock); if (uaddr) { ret = is_range_tree_set(&arena->rt, pgoff, page_cnt); @@ -528,32 +537,51 @@ static long arena_alloc_pages(struct bpf_arena *arena, long uaddr, long page_cnt if (ret) goto out_free_pages; - struct apply_range_data data = { .pages = pages, .i = 0 }; - ret = bpf_map_alloc_pages(&arena->map, node_id, page_cnt, pages); - if (ret) - goto out; - + remaining = page_cnt; uaddr32 = (u32)(arena->user_vm_start + pgoff * PAGE_SIZE); - /* Earlier checks made sure that uaddr32 + page_cnt * PAGE_SIZE - 1 - * will not overflow 32-bit. Lower 32-bit need to represent - * contiguous user address range. - * Map these pages at kern_vm_start base. - * kern_vm_start + uaddr32 + page_cnt * PAGE_SIZE - 1 can overflow - * lower 32-bit and it's ok. - */ - ret = apply_to_page_range(&init_mm, kern_vm_start + uaddr32, - page_cnt << PAGE_SHIFT, apply_range_set_cb, &data); - if (ret) { - for (i = 0; i < page_cnt; i++) - __free_page(pages[i]); - goto out; + + while(remaining) { + long this_batch = min(remaining, alloc_pages); + /* zeroing is needed, since alloc_pages_bulk() only fills in non-zero entries */ + memset(pages, 0, this_batch * sizeof(struct page *)); + data.i = 0; + + ret = bpf_map_alloc_pages(&arena->map, node_id, this_batch, pages); + if (ret) + goto out; + + /* Earlier checks made sure that uaddr32 + page_cnt * PAGE_SIZE - 1 + * will not overflow 32-bit. Lower 32-bit need to represent + * contiguous user address range. + * Map these pages at kern_vm_start base. + * kern_vm_start + uaddr32 + page_cnt * PAGE_SIZE - 1 can overflow + * lower 32-bit and it's ok. + */ + ret = apply_to_page_range(&init_mm, + kern_vm_start + uaddr32 + (mapped << PAGE_SHIFT), + this_batch << PAGE_SHIFT, apply_range_set_cb, &data); + if (ret) { + /* data.i pages were mapped, account them and free the remaining */ + mapped += data.i; + for (i = data.i; i < this_batch; i++) + __free_page(pages[i]); + goto out; + } + + mapped += this_batch; + remaining -= this_batch; } - kvfree(pages); + mutex_unlock(&arena->lock); + kfree_nolock(pages); return clear_lo32(arena->user_vm_start) + uaddr32; out: - range_tree_set(&arena->rt, pgoff, page_cnt); + range_tree_set(&arena->rt, pgoff + mapped, page_cnt - mapped); + mutex_unlock(&arena->lock); + if (mapped) + arena_free_pages(arena, clear_lo32(arena->user_vm_start) + uaddr32, mapped); out_free_pages: - kvfree(pages); + mutex_unlock(&arena->lock); + kfree_nolock(pages); return 0; } -- 2.47.1