From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.5 required=3.0 tests=BAYES_00, BUG6152_INVALID_DATE_TZ_ABSURD,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,INVALID_DATE_TZ_ABSURD, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C4889C43446 for ; Fri, 17 Jul 2020 23:49:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 954FA2074B for ; Fri, 17 Jul 2020 23:49:03 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="jqjm1ThX"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="hvttdDGo" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728779AbgGQXs7 (ORCPT ); Fri, 17 Jul 2020 19:48:59 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45832 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726851AbgGQXs5 (ORCPT ); Fri, 17 Jul 2020 19:48:57 -0400 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B4F96C0619D2 for ; Fri, 17 Jul 2020 16:48:56 -0700 (PDT) From: John Ogness DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1595029734; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=Av9fM2f8uH9etrUiMMqL96ohpvfyJ+3f/7Yr99QyEKg=; b=jqjm1ThXfR4b11Qw/EGA56phbZnhjJAEqpRU/6k/FQpLXOKuanWd9LqeCNjOQhOmzz0hAO Ju7PZZX0boDhi0NpxyvrqGE4lltW6JD5s86PdpGqw1Mf3ifTUr9qPdaB80SwU59QWhLaiq uY7GwnSB1W52J5vQpxZnuwnMUIUlE+QnvYb1UjGv2ZKBxZ5erBkWQxzJh+3fIvzwevHKCb anZWrfNILrWw0Msfix+rkTt1q2a4n7bJcgzpQQkHOsMDDURImsKwo0qCFy79VWG2VTdnMp xr3YRrhO8rDXiBRJW35XKaboDxonTa8uT2+lZ3+OWUx5cM6PZXTRxmJ6qHnjcQ== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1595029734; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=Av9fM2f8uH9etrUiMMqL96ohpvfyJ+3f/7Yr99QyEKg=; b=hvttdDGogkUAaovuyUbES7Csk8Qm14g4/9F0jp/CrWcJB7aYdd/1sXI4ng9sduWkToSUTq y0YXURXjUrNP5RAA== To: Petr Mladek Cc: Sergey Senozhatsky , Sergey Senozhatsky , Steven Rostedt , Linus Torvalds , Greg Kroah-Hartman , Peter Zijlstra , Thomas Gleixner , kexec@lists.infradead.org, linux-kernel@vger.kernel.org Subject: [PATCH 1/4] printk: ringbuffer: support dataless records Date: Sat, 18 Jul 2020 01:54:15 +0206 Message-Id: <20200717234818.8622-2-john.ogness@linutronix.de> In-Reply-To: <20200717234818.8622-1-john.ogness@linutronix.de> References: <20200717234818.8622-1-john.ogness@linutronix.de> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org In order to support storage of continuous lines, dataless records must be allowed. For example, these are generated with the legal calls: pr_info(""); pr_cont("\n"); Currently dataless records are denoted by INVALID_LPOS in order to recognize failed prb_reserve() calls. Change the code to use two different identifiers (FAILED_LPOS and NO_LPOS) to distinguish between failed prb_reserve() records and successful dataless records. Signed-off-by: John Ogness --- kernel/printk/printk_ringbuffer.c | 58 ++++++++++++++----------------- kernel/printk/printk_ringbuffer.h | 15 ++++---- 2 files changed, 35 insertions(+), 38 deletions(-) diff --git a/kernel/printk/printk_ringbuffer.c b/kernel/printk/printk_ringbuffer.c index 7355ca99e852..54b0a6324dbf 100644 --- a/kernel/printk/printk_ringbuffer.c +++ b/kernel/printk/printk_ringbuffer.c @@ -264,6 +264,9 @@ /* Determine how many times the data array has wrapped. */ #define DATA_WRAPS(data_ring, lpos) ((lpos) >> (data_ring)->size_bits) +/* Determine if a logical position refers to a data-less block. */ +#define LPOS_DATALESS(lpos) ((lpos) & 1UL) + /* Get the logical position at index 0 of the current wrap. */ #define DATA_THIS_WRAP_START_LPOS(data_ring, lpos) \ ((lpos) & ~DATA_SIZE_MASK(data_ring)) @@ -320,21 +323,13 @@ static unsigned int to_blk_size(unsigned int size) * block does not exceed the maximum possible size that could fit within the * ringbuffer. This function provides that basic size check so that the * assumption is safe. - * - * Writers are also not allowed to write 0-sized (data-less) records. Such - * records are used only internally by the ringbuffer. */ static bool data_check_size(struct prb_data_ring *data_ring, unsigned int size) { struct prb_data_block *db = NULL; - /* - * Writers are not allowed to write data-less records. Such records - * are used only internally by the ringbuffer to denote records where - * their data failed to allocate or have been lost. - */ if (size == 0) - return false; + return true; /* * Ensure the alignment padded size could possibly fit in the data @@ -568,8 +563,8 @@ static bool data_push_tail(struct printk_ringbuffer *rb, unsigned long tail_lpos; unsigned long next_lpos; - /* If @lpos is not valid, there is nothing to do. */ - if (lpos == INVALID_LPOS) + /* If @lpos is from a data-less block, there is nothing to do. */ + if (LPOS_DATALESS(lpos)) return true; /* @@ -962,8 +957,8 @@ static char *data_alloc(struct printk_ringbuffer *rb, if (size == 0) { /* Specify a data-less block. */ - blk_lpos->begin = INVALID_LPOS; - blk_lpos->next = INVALID_LPOS; + blk_lpos->begin = NO_LPOS; + blk_lpos->next = NO_LPOS; return NULL; } @@ -976,8 +971,8 @@ static char *data_alloc(struct printk_ringbuffer *rb, if (!data_push_tail(rb, data_ring, next_lpos - DATA_SIZE(data_ring))) { /* Failed to allocate, specify a data-less block. */ - blk_lpos->begin = INVALID_LPOS; - blk_lpos->next = INVALID_LPOS; + blk_lpos->begin = FAILED_LPOS; + blk_lpos->next = FAILED_LPOS; return NULL; } @@ -1025,6 +1020,10 @@ static char *data_alloc(struct printk_ringbuffer *rb, static unsigned int space_used(struct prb_data_ring *data_ring, struct prb_data_blk_lpos *blk_lpos) { + /* Data-less blocks take no space. */ + if (LPOS_DATALESS(blk_lpos->begin)) + return 0; + if (DATA_WRAPS(data_ring, blk_lpos->begin) == DATA_WRAPS(data_ring, blk_lpos->next)) { /* Data block does not wrap. */ return (DATA_INDEX(data_ring, blk_lpos->next) - @@ -1080,11 +1079,8 @@ bool prb_reserve(struct prb_reserved_entry *e, struct printk_ringbuffer *rb, if (!data_check_size(&rb->text_data_ring, r->text_buf_size)) goto fail; - /* Records are allowed to not have dictionaries. */ - if (r->dict_buf_size) { - if (!data_check_size(&rb->dict_data_ring, r->dict_buf_size)) - goto fail; - } + if (!data_check_size(&rb->dict_data_ring, r->dict_buf_size)) + goto fail; /* * Descriptors in the reserved state act as blockers to all further @@ -1212,10 +1208,8 @@ static char *get_data(struct prb_data_ring *data_ring, struct prb_data_block *db; /* Data-less data block description. */ - if (blk_lpos->begin == INVALID_LPOS && - blk_lpos->next == INVALID_LPOS) { + if (LPOS_DATALESS(blk_lpos->begin) && LPOS_DATALESS(blk_lpos->next)) return NULL; - } /* Regular data block: @begin less than @next and in same wrap. */ if (DATA_WRAPS(data_ring, blk_lpos->begin) == DATA_WRAPS(data_ring, blk_lpos->next) && @@ -1355,11 +1349,11 @@ static int desc_read_committed_seq(struct prb_desc_ring *desc_ring, /* * A descriptor in the reusable state may no longer have its data - * available; report it as a data-less record. Or the record may - * actually be a data-less record. + * available; report it as existing but with lost data. Or the record + * may actually be a record with lost data. */ if (d_state == desc_reusable || - (blk_lpos->begin == INVALID_LPOS && blk_lpos->next == INVALID_LPOS)) { + (blk_lpos->begin == FAILED_LPOS && blk_lpos->next == FAILED_LPOS)) { return -ENOENT; } @@ -1402,7 +1396,9 @@ static int prb_read(struct printk_ringbuffer *rb, u64 seq, /* Copy text data. If it fails, this is a data-less record. */ if (!copy_data(&rb->text_data_ring, &desc.text_blk_lpos, desc.info.text_len, r->text_buf, r->text_buf_size, line_count)) { - return -ENOENT; + /* Report an error if there should have been data. */ + if (desc.info.text_len != 0) + return -ENOENT; } /* @@ -1659,10 +1655,10 @@ void prb_init(struct printk_ringbuffer *rb, descs[_DESCS_COUNT(descbits) - 1].info.seq = 0; atomic_long_set(&(descs[_DESCS_COUNT(descbits) - 1].state_var), DESC0_SV(descbits)); - descs[_DESCS_COUNT(descbits) - 1].text_blk_lpos.begin = INVALID_LPOS; - descs[_DESCS_COUNT(descbits) - 1].text_blk_lpos.next = INVALID_LPOS; - descs[_DESCS_COUNT(descbits) - 1].dict_blk_lpos.begin = INVALID_LPOS; - descs[_DESCS_COUNT(descbits) - 1].dict_blk_lpos.next = INVALID_LPOS; + descs[_DESCS_COUNT(descbits) - 1].text_blk_lpos.begin = FAILED_LPOS; + descs[_DESCS_COUNT(descbits) - 1].text_blk_lpos.next = FAILED_LPOS; + descs[_DESCS_COUNT(descbits) - 1].dict_blk_lpos.begin = FAILED_LPOS; + descs[_DESCS_COUNT(descbits) - 1].dict_blk_lpos.next = FAILED_LPOS; } /** diff --git a/kernel/printk/printk_ringbuffer.h b/kernel/printk/printk_ringbuffer.h index 3e46a7423c13..e6302da041f9 100644 --- a/kernel/printk/printk_ringbuffer.h +++ b/kernel/printk/printk_ringbuffer.h @@ -120,12 +120,13 @@ struct prb_reserved_entry { #define DESC_FLAGS_MASK (DESC_COMMITTED_MASK | DESC_REUSE_MASK) #define DESC_ID_MASK (~DESC_FLAGS_MASK) #define DESC_ID(sv) ((sv) & DESC_ID_MASK) -#define INVALID_LPOS 1 +#define FAILED_LPOS 0x1 +#define NO_LPOS 0x3 -#define INVALID_BLK_LPOS \ +#define FAILED_BLK_LPOS \ { \ - .begin = INVALID_LPOS, \ - .next = INVALID_LPOS, \ + .begin = FAILED_LPOS, \ + .next = FAILED_LPOS, \ } /* @@ -147,7 +148,7 @@ struct prb_reserved_entry { * * To satisfy Req1, the tail initially points to a descriptor that is * minimally initialized (having no data block, i.e. data-less with the - * data block's lpos @begin and @next values set to INVALID_LPOS). + * data block's lpos @begin and @next values set to FAILED_LPOS). * * To satisfy Req2, the initial tail descriptor is initialized to the * reusable state. Readers recognize reusable descriptors as existing @@ -242,8 +243,8 @@ static struct prb_desc _##name##_descs[_DESCS_COUNT(descbits)] = { \ /* reusable */ \ .state_var = ATOMIC_INIT(DESC0_SV(descbits)), \ /* no associated data block */ \ - .text_blk_lpos = INVALID_BLK_LPOS, \ - .dict_blk_lpos = INVALID_BLK_LPOS, \ + .text_blk_lpos = FAILED_BLK_LPOS, \ + .dict_blk_lpos = FAILED_BLK_LPOS, \ }, \ }; \ static struct printk_ringbuffer name = { \ -- 2.20.1