[Crash-utility] Negative NR_WRITEBACK counter

Hello Everyone, I am analysing a kernel crash dump (vmcore) captured from RHEL-5 kernel version (2.6.18-371.4.1.el5) and found that the value of "NR_WRITEBACK" counter is negative (-126). $ rpm -q crash crash-7.0.6-2.el6.x86_64 crash> sys | grep -e RELEASE -e MACHINE -e MEMORY RELEASE: 2.6.18-371.4.1.el5 MACHINE: x86_64 (3000 Mhz) MEMORY: 31.5 GB crash> kmem -z | grep -e ZONE -e NR_WRITEBACK NODE: 0 ZONE: 0 ADDR: ffff810000032000 NAME: "DMA" NR_WRITEBACK: 0 NODE: 0 ZONE: 1 ADDR: ffff810000032b00 NAME: "DMA32" NR_WRITEBACK: 0 NODE: 0 ZONE: 2 ADDR: ffff810000033600 NAME: "Normal" NR_WRITEBACK: -126 <<<< NODE: 0 ZONE: 3 ADDR: ffff810000034100 NAME: "HighMem" crash> kmem -V | grep -e NR_WRITEBACK NR_WRITEBACK: -126 <<<< crash> vm_stat vm_stat = $1 = {{ counter = 1106459 }, { counter = 2940354 }, { counter = 6341366 }, { counter = 301750 }, { counter = 245858 }, { counter = 438 }, { counter = -126 // NR_WRITEBACK <<<< }, { counter = 0 }, { counter = 0 }, { counter = 19687071384 }, { counter = 0 }, { counter = 0 }, { counter = 29247123 }, { counter = 19687071384 }, { counter = 0 }} As we're running a 64 bit kernel and the counters are signed long, so this is very unlikely to be a counter overflow. I need pointers and suggestions to determine the *cause* of negative counter from vmcore. Additional Information: $ git show ce866b34ae1b7f1ce60234cf65855886ac7e7d30 [..] diff --git a/drivers/base/node.c b/drivers/base/node.c index 6fed520..a7b3dcb 100644 --- a/drivers/base/node.c +++ b/drivers/base/node.c @@ -49,9 +49,6 @@ static ssize_t node_read_meminfo(struct sys_device * dev, char * buf) get_page_state_node(&ps, nid); __get_zone_counts(&active, &inactive, &free, NODE_DATA(nid)); - /* Check for negative values in these approximate counters */ - if ((long)ps.nr_writeback < 0) - ps.nr_writeback = 0; n = sprintf(buf, "\n" "Node %d MemTotal: %8lu kB\n" [..] Thank you ! -- BKS