Commit 4260e0e5 authored by John Ogness's avatar John Ogness Committed by Petr Mladek
Browse files

printk: consolidate kmsg_dump_get_buffer/syslog_print_all code 



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: default avatarJohn Ogness <john.ogness@linutronix.de>
Reviewed-by: default avatarPetr Mladek <pmladek@suse.com>
Signed-off-by: default avatarPetr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20210303101528.29901-7-john.ogness@linutronix.de
parent 726b5097

kernel/printk/printk.c

+50 −37
Original line number Diff line number Diff line
@@ -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