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 E3A19149E17 for ; Wed, 17 Dec 2025 18:45:00 +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=1765997102; cv=none; b=cLuUtktWWUNGgO/I+bbdzd1oTZaQ0HJG8RJucSW5vAW/3LIdF8NoI17kIu2/8tAFcXtnDvUN2GmhO189m7BkM+23t2+D8S5zhi0cJoliP8djhVzKRraoqKOS1bV7OIdR64yta6oGyPGOc40S0Gz7j7q8VQWi3/Vuy3xwvK9hKr0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1765997102; c=relaxed/simple; bh=1KVkw0pkCoOR9hwStc7EOid+IQ3Z9fplcVeAbvppwYY=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=eeaWRe2o41qP318+15Q80rbVGd0uX9MqxS8sDeWgMr+mRVfSDcWw1rsOK/l7narO11LXDXOAbGdwYTMBaXcdALmS5JfyPjDK2rbJzYcDZdMYQFTI96qBSqhTOAqjV5U5sSoMhmCHoWFDTPXlnv1zFmVfF4sjVRznTGA9HMBfyUE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=lBQKrwet; 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="lBQKrwet" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 288DFC4CEF5; Wed, 17 Dec 2025 18:45:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1765997100; bh=1KVkw0pkCoOR9hwStc7EOid+IQ3Z9fplcVeAbvppwYY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=lBQKrwetmEtSAj2wedhYEN1n0EOkaf8tHGy7E/MWJiFrohkG7dNKPCdt26JN5nMdw LhDfO7SBUCmT8hFZ2y7hM/qcR0ni1FXYPPLjmf7ew/rfIc9Xbg0oTo03+eka+/Ys5Q Rt1NzSF7wzD7roLO4l/VlcUZIPWbcscHaYJY3d9iVDKzE+rI2VcNBqAK1LgGtpRKgw VDLmTWicUH5hJ7zpUTPYIneLLPMWBNfqwfk4ysyd5E16QjtK94fs1zzjD8MTvteJKY ACw2Zlyx1iKjRMjihWpSMlI9MR2f9nUwgp9mlxv3bwPb5AOUVgh4wfr8bnAeW/h9S9 RdxhoiBVv+iDQ== 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 v6 2/4] bpf: arena: use kmalloc_nolock() in place of kvcalloc() Date: Wed, 17 Dec 2025 10:44:33 -0800 Message-ID: <20251217184438.3557859-3-puranjay@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20251217184438.3557859-1-puranjay@kernel.org> References: <20251217184438.3557859-1-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 | 80 ++++++++++++++++++++++++++++++---------------- 1 file changed, 53 insertions(+), 27 deletions(-) diff --git a/kernel/bpf/arena.c b/kernel/bpf/arena.c index 039f25fc074b..9409ca7ccc4e 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; @@ -493,8 +495,10 @@ 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 mapped = 0; + long remaining, mapped = 0; + long alloc_pages; long pgoff = 0; u32 uaddr32; int ret, i; @@ -511,17 +515,19 @@ 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); if (ret) - goto out_free_pages; + goto out_unlock_free_pages; ret = range_tree_clear(&arena->rt, pgoff, page_cnt); } else { ret = pgoff = range_tree_find(&arena->rt, page_cnt); @@ -529,37 +535,57 @@ static long arena_alloc_pages(struct bpf_arena *arena, long uaddr, long page_cnt ret = range_tree_clear(&arena->rt, pgoff, 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; + goto out_unlock_free_pages; + 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) { - mapped = data.i; - for (i = mapped; 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 *)); + + 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. + */ + data.i = 0; + 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 + mapped, page_cnt - mapped); + mutex_unlock(&arena->lock); if (mapped) arena_free_pages(arena, uaddr32, mapped); + goto out_free_pages; +out_unlock_free_pages: + mutex_unlock(&arena->lock); out_free_pages: - kvfree(pages); + kfree_nolock(pages); return 0; } -- 2.47.3