Messages in this thread Patch in this message | | | From | John Ogness <> | Subject | [PATCH printk-rework 03/12] printk: consolidate kmsg_dump_get_buffer/syslog_print_all code | Date | Tue, 26 Jan 2021 22:21:42 +0106 |
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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> --- kernel/printk/printk.c | 71 ++++++++++++++++++++++++------------------ 1 file changed, 41 insertions(+), 30 deletions(-)
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index 1929aa372e7f..ec2174882b8e 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -1421,6 +1421,41 @@ 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. + */ +static u64 find_first_fitting_seq(u64 start_seq, u64 max_seq, size_t size, + struct printk_info *info, bool syslog, bool time) +{ + 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); + } + + /* + * 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. + */ + if (seq < max_seq) + max_seq = seq; + 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; @@ -1492,7 +1527,6 @@ 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; char *text; int len = 0; @@ -1509,15 +1543,7 @@ 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); - - /* move first record forward until length fits into the buffer */ - prb_for_each_info(clear_seq, prb, seq, &info, &line_count) { - if (len <= size) - break; - len -= get_record_print_text_size(&info, line_count, true, time); - } + seq = find_first_fitting_seq(clear_seq, -1, size, &info, true, time); prb_rec_init_rd(&r, &info, text, LOG_LINE_MAX + PREFIX_MAX); @@ -3410,7 +3436,6 @@ 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; @@ -3436,26 +3461,12 @@ 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, &info, syslog, time); /* Keep track of the last message for the next iteration. */ next_seq = seq; -- 2.20.1
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