Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932213AbaGUMcP (ORCPT ); Mon, 21 Jul 2014 08:32:15 -0400 Received: from mail-ig0-f173.google.com ([209.85.213.173]:41819 "EHLO mail-ig0-f173.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932127AbaGUMcN (ORCPT ); Mon, 21 Jul 2014 08:32:13 -0400 Message-ID: <53CD0852.2030706@linaro.org> Date: Mon, 21 Jul 2014 07:32:18 -0500 From: Alex Elder User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.6.0 MIME-Version: 1.0 To: =?ISO-8859-1?Q?Petr_Ml=E1dek?= CC: akpm@linux-foundation.org, kay@vrfy.org, bp@suse.de, john.stultz@linaro.org, jack@suse.cz, linux-kernel@vger.kernel.org Subject: Re: [PATCH v4 6/7] printk: insert newline for truncated records References: <1405718885-11227-1-git-send-email-elder@linaro.org> <1405718885-11227-7-git-send-email-elder@linaro.org> <20140721115706.GC20751@pathway.suse.cz> In-Reply-To: <20140721115706.GC20751@pathway.suse.cz> X-Enigmail-Version: 1.5.2 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 07/21/2014 06:57 AM, Petr Ml?dek wrote: > On Fri 2014-07-18 16:28:04, Alex Elder wrote: >> If a log record has LOG_PREFIX set, its predecessor record should be >> terminated if it was marked LOG_CONT. >> >> In devkmsg_read(), this condition was being ignored, which would >> lead to such records showing up combined when reading /dev/kmsg. >> Fix this oversight. >> >> We should similarly insert a newline in msg_print_text() in this >> case, to avoid formatted records getting merged. >> >> Suggested-by: Petr Ml?dek >> Signed-off-by: Alex Elder >> --- >> kernel/printk/printk.c | 18 +++++++++++++++--- >> 1 file changed, 15 insertions(+), 3 deletions(-) >> >> diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c >> index e9f0632..a5ad81c 100644 >> --- a/kernel/printk/printk.c >> +++ b/kernel/printk/printk.c >> @@ -575,6 +575,7 @@ static ssize_t devkmsg_read(struct file *file, char __user *buf, >> char cont; >> size_t len; >> ssize_t ret; >> + bool insert_newline; >> >> if (!user) >> return -EBADF; >> @@ -626,7 +627,10 @@ static ssize_t devkmsg_read(struct file *file, char __user *buf, >> else >> cont = '-'; >> >> - len = sprintf(user->buf, "%u,%llu,%llu,%c;", >> + /* Insert a newline if the previous line was not terminated properly */ >> + insert_newline = (user->prev & LOG_CONT) && (msg->flags & LOG_PREFIX); >> + len = sprintf(user->buf, "%s%u,%llu,%llu,%c;", >> + insert_newline ? "\n" : "", >> (msg->facility << 3) | msg->level, >> user->seq, ts_usec, cont); >> user->prev = msg->flags; >> @@ -999,10 +1003,12 @@ static size_t msg_print_text(const struct printk_log *msg, enum log_flags prev, >> { >> const char *text = log_text(msg); >> size_t text_size = msg->text_len; >> + size_t len = 0; >> + bool insert_newline; >> bool prefix = true; >> bool newline = true; >> - size_t len = 0; >> >> + insert_newline = (prev & LOG_CONT) && (msg->flags & LOG_PREFIX); >> if ((prev & LOG_CONT) && !(msg->flags & LOG_PREFIX)) >> prefix = false; >> >> @@ -1023,9 +1029,13 @@ static size_t msg_print_text(const struct printk_log *msg, enum log_flags prev, >> >> if (buf) { >> if (print_prefix(msg, syslog, NULL) + >> - text_len + 1 >= size - len) >> + text_len + 2 >= size - len) > > It counts the '\n' even when it is not used. > I think that it is even wrong that it calculates prefix when it is not used. That's true, and I have yet another un-posted patch that addresses this problem (well the second one). I am not going to fix this problem in this patch, but the fix is coming. Now that you're looking at the code I'm touching, you're seeing the same things I did... I think I'll start posting that series later today or tomorrow. I just hate to get too far ahead of myself. >> break; >> >> + if (insert_newline) { >> + insert_newline = false; >> + buf[len++] = '\n'; >> + } >> if (prefix) >> len += print_prefix(msg, syslog, buf + len); >> memcpy(buf + len, text, text_len); >> @@ -1034,6 +1044,8 @@ static size_t msg_print_text(const struct printk_log *msg, enum log_flags prev, >> buf[len++] = '\n'; >> } else { >> /* SYSLOG_ACTION_* buffer size only calculation */ >> + if (insert_newline) >> + len++; > > You forgot "insert_newline = false" here. Yes you're right. It's good that you're reviewing this. (The patches I have not yet posted affect this area of code, and should eliminate this block...) >> if (prefix) >> len += print_prefix(msg, syslog, NULL); >> len += text_len; > > It is just matter of personal style but I would suggest to do this > before the do-while cycle: > > /* Force newline if the previous text was not properly finished */ > if ((prev & LOG_CONT) && (msg->flags & LOG_PREFIX) && (len < size)) { > if (buf) > buf[len++] = '\n'; > else > len++; > } > > IMHO, it is more clear. The do-while cycle already is complex enough. I agree with this. It's a one-time thing and doesn't belong in the loop. When you suggested inserting the newline I think I didn't think it through completely. I will do this. > BTW: This is relared to the first patch. I would either patch all > three locations in one patch or better split it into three patches. I am keeping the first patch separate from this one. I think the first is related (in that we improve readability by inserting some newlines) but it's really addressing a different problem. Meanwhile, this patch is addressing essentially the same problem in two spots, so I'd like to keep these together rather than splitting it in two. I will move this patch earlier in the series, however, making it follow patch 1. I may be misunderstanding what you mean though. Is what I propose OK with you? Thank you. -Alex > > Best Regards, > Petr > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/