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printk: consolidate kmsg_dump_get_buffer/syslog_print_all code

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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>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20210303101528.29901-7-john.ogness@linutronix.de
This commit is contained in:
John Ogness 2021-03-03 11:15:19 +01:00 committed by Petr Mladek
parent 726b509770
commit 4260e0e551
1 changed files with 50 additions and 37 deletions
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87
kernel/printk/printk.c
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@ -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