printk_ringbuffer: Fix space_used() when blk_lpos->next overflows

Since commit 67e1b0052f6b ("printk_ringbuffer: don't needlessly wrap data
blocks around") blk_lpos is treated as not wrapped when blk_lpos->next
overflows to the start of data_ring. We use the indices of blk_lpos->next
and blk_lpos->start to calculate the size of the data_block. This computes
zero minus a small positive value, resulting in underflow and an
unexpectedly large value. Simply using the original lpos with wrap-counts
solves the problem.

Fixes: 67e1b0052f6b ("printk_ringbuffer: don't needlessly wrap data blocks around")
Signed-off-by: Wang Wensheng <wsw9603@163.com>
Reviewed-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Link: https://patch.msgid.link/20261004075755.363989-1-wsw9603@163.com
Signed-off-by: Petr Mladek <pmladek@suse.com>

0 files changed, 0 insertions, 0 deletions