On Mon 2018-06-25 23:44:07, Sergey Senozhatsky wrote: > On (06/25/18 10:37), Steven Rostedt wrote: > > > > Is IMHO rather ugly. > > Either way works for me. So I'll leave it to you and Petr to decide :) > > > And the original patch has one more advantage. If buf and clear are > > both NULL/zero, we don't take any locks. > > But we never use syslog_print_all(buf = NULL, clear = false). It's either > NULL/true [move forward clear idx, do not copy to user], or !NULL/use defined > value [copy to user, move or don't move clear idx forward]
Yup, I suggest the following version as a compromise. It has the code duplication but I agree that it is negligible. Otherwise, it looks cleaner. >From be6e161b3d75830e710c3ada56f5eeb615fae002 Mon Sep 17 00:00:00 2001 From: Namit Gupta <[email protected]> Date: Wed, 20 Jun 2018 19:26:19 +0530 Subject: [PATCH] printk: remove unnecessary kmalloc() from syslog during clear When the request is only for clearing logs, there is no need for allocation/deallocation. Only the indexes need to be reset and returned. This patch implements this simple case separately. And syslog_print_all() is always called with a valid buf and could use a more sane indentation. Link: http://lkml.kernel.org/r/20180620135951epcas5p3bd2a8f25ec689ca333bce861b527dba2~54wykct0_3155531555epcas5...@epcas5p3.samsung.com Cc: [email protected] Cc: [email protected] Cc: [email protected] Signed-off-by: Namit Gupta <[email protected]> Signed-off-by: Himanshu Maithani <[email protected]> Reviewed-by: Steven Rostedt (VMware) <[email protected]> Reviewed-by: Sergey Senozhatsky <[email protected]> Signed-off-by: Petr Mladek <[email protected]> --- kernel/printk/printk.c | 111 ++++++++++++++++++++++++++----------------------- 1 file changed, 58 insertions(+), 53 deletions(-) diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index 247808333ba4..588f23c9c14f 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -1352,71 +1352,68 @@ static int syslog_print_all(char __user *buf, int size, bool clear) { char *text; int len = 0; + u64 next_seq; + u64 seq; + u32 idx; text = kmalloc(LOG_LINE_MAX + PREFIX_MAX, GFP_KERNEL); if (!text) return -ENOMEM; logbuf_lock_irq(); - if (buf) { - u64 next_seq; - u64 seq; - u32 idx; + /* + * Find first record that fits, including all following records, + * into the user-provided buffer for this dump. + */ + seq = clear_seq; + idx = clear_idx; + while (seq < log_next_seq) { + struct printk_log *msg = log_from_idx(idx); - /* - * Find first record that fits, including all following records, - * into the user-provided buffer for this dump. - */ - seq = clear_seq; - idx = clear_idx; - while (seq < log_next_seq) { - struct printk_log *msg = log_from_idx(idx); - - len += msg_print_text(msg, true, NULL, 0); - idx = log_next(idx); - seq++; - } + len += msg_print_text(msg, true, NULL, 0); + idx = log_next(idx); + seq++; + } - /* move first record forward until length fits into the buffer */ - seq = clear_seq; - idx = clear_idx; - while (len > size && seq < log_next_seq) { - struct printk_log *msg = log_from_idx(idx); + /* move first record forward until length fits into the buffer */ + seq = clear_seq; + idx = clear_idx; + while (len > size && seq < log_next_seq) { + struct printk_log *msg = log_from_idx(idx); - len -= msg_print_text(msg, true, NULL, 0); - idx = log_next(idx); - seq++; - } + len -= msg_print_text(msg, true, NULL, 0); + idx = log_next(idx); + seq++; + } - /* last message fitting into this dump */ - next_seq = log_next_seq; + /* last message fitting into this dump */ + next_seq = log_next_seq; - len = 0; - while (len >= 0 && seq < next_seq) { - struct printk_log *msg = log_from_idx(idx); - int textlen; + len = 0; + while (len >= 0 && seq < next_seq) { + struct printk_log *msg = log_from_idx(idx); + int textlen; - textlen = msg_print_text(msg, true, text, - LOG_LINE_MAX + PREFIX_MAX); - if (textlen < 0) { - len = textlen; - break; - } - idx = log_next(idx); - seq++; + textlen = msg_print_text(msg, true, text, + LOG_LINE_MAX + PREFIX_MAX); + if (textlen < 0) { + len = textlen; + break; + } + idx = log_next(idx); + seq++; - logbuf_unlock_irq(); - if (copy_to_user(buf + len, text, textlen)) - len = -EFAULT; - else - len += textlen; - logbuf_lock_irq(); - - if (seq < log_first_seq) { - /* messages are gone, move to next one */ - seq = log_first_seq; - idx = log_first_idx; - } + logbuf_unlock_irq(); + if (copy_to_user(buf + len, text, textlen)) + len = -EFAULT; + else + len += textlen; + logbuf_lock_irq(); + + if (seq < log_first_seq) { + /* messages are gone, move to next one */ + seq = log_first_seq; + idx = log_first_idx; } } @@ -1430,6 +1427,14 @@ static int syslog_print_all(char __user *buf, int size, bool clear) return len; } +static void syslog_clear(void) +{ + logbuf_lock_irq(); + clear_seq = log_next_seq; + clear_idx = log_next_idx; + logbuf_unlock_irq(); +} + int do_syslog(int type, char __user *buf, int len, int source) { bool clear = false; @@ -1474,7 +1479,7 @@ int do_syslog(int type, char __user *buf, int len, int source) break; /* Clear ring buffer */ case SYSLOG_ACTION_CLEAR: - syslog_print_all(NULL, 0, true); + syslog_clear(); break; /* Disable logging to console */ case SYSLOG_ACTION_CONSOLE_OFF: -- 2.13.7
