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printk: refactor kmsg_dump_get_buffer() 

kmsg_dump_get_buffer() requires nearly the same logic as
syslog_print_all(), but uses different variable names and
does not make use of the ringbuffer loop macros. Modify
kmsg_dump_get_buffer() so that the implementation is as similar
to syslog_print_all() as possible.

A follow-up commit will move this common logic into a
separate helper function.

Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20210303101528.29901-6-john.ogness@linutronix.de
This commit is contained in:
John Ogness 2021-03-03 11:15:18 +01:00 committed by Petr Mladek
parent e831e400f7
commit 726b509770
2 changed files with 34 additions and 30 deletions
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2
include/linux/kmsg_dump.h
View File

@ -62,7 +62,7 @@ bool kmsg_dump_get_line(struct kmsg_dumper *dumper, bool syslog,
char *line, size_t size, size_t *len);
bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog,
char *buf, size_t size, size_t *len);
char *buf, size_t size, size_t *len_out);
void kmsg_dump_rewind_nolock(struct kmsg_dumper *dumper);

62
kernel/printk/printk.c
View File

@ -3410,7 +3410,7 @@ EXPORT_SYMBOL_GPL(kmsg_dump_get_line);
* @syslog: include the "<4>" prefixes
* @buf: buffer to copy the line to
* @size: maximum size of the buffer
* @len: length of line placed into buffer
* @len_out: length of line placed into buffer
*
* Start at the end of the kmsg buffer and fill the provided buffer
* with as many of the *youngest* kmsg records that fit into it.
@ -3424,7 +3424,7 @@ EXPORT_SYMBOL_GPL(kmsg_dump_get_line);
* read.
*/
bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog,
char *buf, size_t size, size_t *len)
char *buf, size_t size, size_t *len_out)
{
struct printk_info info;
unsigned int line_count;
@ -3432,12 +3432,10 @@ bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog,
unsigned long flags;
u64 seq;
u64 next_seq;
size_t l = 0;
size_t len = 0;
bool ret = false;
bool time = printk_time;
prb_rec_init_rd(&r, &info, buf, size);
if (!dumper->active || !buf || !size)
goto out;
@ -3455,48 +3453,54 @@ bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog,
goto out;
}
/* calculate length of entire buffer */
seq = dumper->cur_seq;
while (prb_read_valid_info(prb, seq, &info, &line_count)) {
if (r.info->seq >= dumper->next_seq)
/*
* Find first record that fits, including all following records,
* into the user-provided buffer for this dump.
*/
prb_for_each_info(dumper->cur_seq, prb, seq, &info, &line_count) {
if (info.seq >= dumper->next_seq)
break;
l += get_record_print_text_size(&info, line_count, syslog, time);
seq = r.info->seq + 1;
len += get_record_print_text_size(&info, line_count, syslog, time);
}
/* move first record forward until length fits into the buffer */
seq = dumper->cur_seq;
while (l >= size && prb_read_valid_info(prb, seq,
&info, &line_count)) {
if (r.info->seq >= dumper->next_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 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;
l -= get_record_print_text_size(&info, line_count, syslog, time);
seq = r.info->seq + 1;
len -= get_record_print_text_size(&info, line_count, syslog, time);
}
/* last message in next interation */
/*
* Next kmsg_dump_get_buffer() invocation will dump block of
* older records stored right before this one.
*/
next_seq = seq;
/* actually read text into the buffer now */
l = 0;
while (prb_read_valid(prb, seq, &r)) {
prb_rec_init_rd(&r, &info, buf, size);
len = 0;
prb_for_each_record(seq, prb, seq, &r) {
if (r.info->seq >= dumper->next_seq)
break;
l += record_print_text(&r, syslog, time);
len += record_print_text(&r, syslog, time);
/* adjust record to store to remaining buffer space */
prb_rec_init_rd(&r, &info, buf + l, size - l);
seq = r.info->seq + 1;
/* Adjust record to store to remaining buffer space. */
prb_rec_init_rd(&r, &info, buf + len, size - len);
}
dumper->next_seq = next_seq;
ret = true;
logbuf_unlock_irqrestore(flags);
out:
if (len)
*len = l;
if (len_out)
*len_out = len;
return ret;
}
EXPORT_SYMBOL_GPL(kmsg_dump_get_buffer);