From: John Ogness <john.ogness@linutronix.de>
To: Petr Mladek <pmladek@suse.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
Steven Rostedt <rostedt@goodmis.org>,
Thomas Gleixner <tglx@linutronix.de>,
linux-kernel@vger.kernel.org
Subject: [PATCH next v3 06/15] printk: consolidate kmsg_dump_get_buffer/syslog_print_all code
Date: Thu, 25 Feb 2021 21:24:29 +0100 [thread overview]
Message-ID: <20210225202438.28985-7-john.ogness@linutronix.de> (raw)
In-Reply-To: <20210225202438.28985-1-john.ogness@linutronix.de>
The logic for finding records to fit into a buffer is the same for
kmsg_dump_get_buffer() and syslog_print_all(). Introduce a helper
function find_first_fitting_seq() to handle this logic.
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
---
kernel/printk/printk.c | 87 ++++++++++++++++++++++++------------------
1 file changed, 50 insertions(+), 37 deletions(-)
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index ed678d84dc51..9a5f9ccc46ea 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -1421,6 +1421,50 @@ static size_t get_record_print_text_size(struct printk_info *info,
return ((prefix_len * line_count) + info->text_len + 1);
}
+/*
+ * Beginning with @start_seq, find the first record where it and all following
+ * records up to (but not including) @max_seq fit into @size.
+ *
+ * @max_seq is simply an upper bound and does not need to exist. If the caller
+ * does not require an upper bound, -1 can be used for @max_seq.
+ */
+static u64 find_first_fitting_seq(u64 start_seq, u64 max_seq, size_t size,
+ bool syslog, bool time)
+{
+ struct printk_info info;
+ unsigned int line_count;
+ size_t len = 0;
+ u64 seq;
+
+ /* Determine the size of the records up to @max_seq. */
+ prb_for_each_info(start_seq, prb, seq, &info, &line_count) {
+ if (info.seq >= max_seq)
+ break;
+ len += get_record_print_text_size(&info, line_count, syslog, time);
+ }
+
+ /*
+ * Adjust the upper bound for the next loop to avoid subtracting
+ * lengths that were never added.
+ */
+ if (seq < max_seq)
+ max_seq = seq;
+
+ /*
+ * Move first record forward until length fits into the buffer. Ignore
+ * newest messages that were not counted in the above cycle. Messages
+ * might appear and get lost in the meantime. This is a best effort
+ * that prevents an infinite loop that could occur with a retry.
+ */
+ prb_for_each_info(start_seq, prb, seq, &info, &line_count) {
+ if (len <= size || info.seq >= max_seq)
+ break;
+ len -= get_record_print_text_size(&info, line_count, syslog, time);
+ }
+
+ return seq;
+}
+
static int syslog_print(char __user *buf, int size)
{
struct printk_info info;
@@ -1492,9 +1536,7 @@ static int syslog_print(char __user *buf, int size)
static int syslog_print_all(char __user *buf, int size, bool clear)
{
struct printk_info info;
- unsigned int line_count;
struct printk_record r;
- u64 max_seq;
char *text;
int len = 0;
u64 seq;
@@ -1510,21 +1552,7 @@ static int syslog_print_all(char __user *buf, int size, bool clear)
* Find first record that fits, including all following records,
* into the user-provided buffer for this dump.
*/
- prb_for_each_info(clear_seq, prb, seq, &info, &line_count)
- len += get_record_print_text_size(&info, line_count, true, time);
-
- /*
- * Set an upper bound for the next loop to avoid subtracting lengths
- * that were never added.
- */
- max_seq = seq;
-
- /* move first record forward until length fits into the buffer */
- prb_for_each_info(clear_seq, prb, seq, &info, &line_count) {
- if (len <= size || info.seq >= max_seq)
- break;
- len -= get_record_print_text_size(&info, line_count, true, time);
- }
+ seq = find_first_fitting_seq(clear_seq, -1, size, true, time);
prb_rec_init_rd(&r, &info, text, LOG_LINE_MAX + PREFIX_MAX);
@@ -3427,7 +3455,6 @@ bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog,
char *buf, size_t size, size_t *len_out)
{
struct printk_info info;
- unsigned int line_count;
struct printk_record r;
unsigned long flags;
u64 seq;
@@ -3455,26 +3482,12 @@ bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog,
/*
* Find first record that fits, including all following records,
- * into the user-provided buffer for this dump.
+ * into the user-provided buffer for this dump. Pass in size-1
+ * because this function (by way of record_print_text()) will
+ * not write more than size-1 bytes of text into @buf.
*/
-
- prb_for_each_info(dumper->cur_seq, prb, seq, &info, &line_count) {
- if (info.seq >= dumper->next_seq)
- break;
- len += get_record_print_text_size(&info, line_count, syslog, time);
- }
-
- /*
- * Move first record forward until length fits into the buffer. Ignore
- * newest messages that were not counted in the above cycle. Messages
- * might appear and get lost in the meantime. This is the best effort
- * that prevents an infinite loop.
- */
- prb_for_each_info(dumper->cur_seq, prb, seq, &info, &line_count) {
- if (len < size || info.seq >= dumper->next_seq)
- break;
- len -= get_record_print_text_size(&info, line_count, syslog, time);
- }
+ seq = find_first_fitting_seq(dumper->cur_seq, dumper->next_seq,
+ size - 1, syslog, time);
/*
* Next kmsg_dump_get_buffer() invocation will dump block of
--
2.20.1
next prev parent reply other threads:[~2021-02-25 20:30 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-25 20:24 [PATCH next v3 00/15] printk: remove logbuf_lock John Ogness
2021-02-25 20:24 ` [PATCH next v3 01/15] um: synchronize kmsg_dumper John Ogness
2021-03-01 16:16 ` Petr Mladek
2021-03-01 16:57 ` Petr Mladek
2021-03-02 8:06 ` John Ogness
2021-03-02 10:12 ` Petr Mladek
2021-02-25 20:24 ` [PATCH next v3 02/15] mtd: mtdoops: " John Ogness
2021-03-01 12:13 ` Petr Mladek
2021-03-02 10:45 ` John Ogness
2021-03-02 12:48 ` Petr Mladek
2021-02-25 20:24 ` [PATCH next v3 03/15] printk: limit second loop of syslog_print_all John Ogness
2021-02-25 20:24 ` [PATCH next v3 04/15] printk: kmsg_dump: remove unused fields John Ogness
2021-02-25 20:24 ` [PATCH next v3 05/15] printk: refactor kmsg_dump_get_buffer() John Ogness
2021-02-25 20:24 ` John Ogness [this message]
2021-02-25 20:24 ` [PATCH next v3 07/15] printk: introduce CONSOLE_LOG_MAX for improved multi-line support John Ogness
2021-03-02 13:54 ` Geert Uytterhoeven
2021-03-02 13:58 ` Geert Uytterhoeven
2021-03-02 14:34 ` John Ogness
2021-02-25 20:24 ` [PATCH next v3 08/15] printk: use seqcount_latch for clear_seq John Ogness
2021-02-25 20:24 ` [PATCH next v3 09/15] printk: use atomic64_t for devkmsg_user.seq John Ogness
2021-02-25 20:24 ` [PATCH next v3 10/15] printk: add syslog_lock John Ogness
2021-03-01 17:07 ` Petr Mladek
2021-02-25 20:24 ` [PATCH next v3 11/15] printk: kmsg_dumper: remove @active field John Ogness
2021-03-01 17:09 ` Petr Mladek
2021-02-25 20:24 ` [PATCH next v3 12/15] printk: introduce a kmsg_dump iterator John Ogness
2021-02-25 21:59 ` Kees Cook
2021-02-26 7:59 ` John Ogness
2021-03-01 18:07 ` Petr Mladek
2021-03-02 13:20 ` John Ogness
2021-03-02 13:55 ` Petr Mladek
2021-02-25 20:24 ` [PATCH next v3 13/15] printk: remove logbuf_lock John Ogness
2021-03-02 12:15 ` Petr Mladek
2021-02-25 20:24 ` [PATCH next v3 14/15] printk: kmsg_dump: remove _nolock() variants John Ogness
2021-02-25 20:24 ` [PATCH next v3 15/15] printk: console: remove unnecessary safe buffer usage John Ogness
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