The patch titled
hugetlb: fix race when reading proc meminfo
has been added to the -mm tree. Its filename is
hugetlb-fix-race-when-reading-proc-meminfo.patch
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The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
------------------------------------------------------
Subject: hugetlb: fix race when reading proc meminfo
From: Eric Paris <eparis@xxxxxxxxxx>
minor nit that hugetlb_report_{,node_}meminfo() does not lock the reading
of nr_huge_pages, free_huge_pages, and friends so this is not an atomic
set of information put into the buffer. If /proc/meminfo is read while
the number of hugetlb pages is in flux it is possible to get incorrect
output such as:
HugePages_Total: 7
HugePages_Free: 8
HugePages_Rsvd: 0
Hugepagesize: 4096 kB
(test available at https://bugzilla.redhat.com/attachment.cgi?id=309864)
With the patch we beat on a number of boxes for hours with the above test
and saw no inconsistencies in the meminfo output.
Signed-off-by: Eric Paris <eparis@xxxxxxxxxx>
Cc: Andy Whitcroft <apw@xxxxxxxxxxxx>
Cc: Mel Gorman <mel@xxxxxxxxx>
Cc: Adam Litke <agl@xxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxxx>
Cc: William Lee Irwin III <wli@xxxxxxxxxxxxxx>
Cc: Hugh Dickins <hugh@xxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/hugetlb.c | 14 ++++++++++++--
1 file changed, 12 insertions(+), 2 deletions(-)
diff -puN mm/hugetlb.c~hugetlb-fix-race-when-reading-proc-meminfo mm/hugetlb.c
--- a/mm/hugetlb.c~hugetlb-fix-race-when-reading-proc-meminfo
+++ a/mm/hugetlb.c
@@ -1455,7 +1455,10 @@ int hugetlb_overcommit_handler(struct ct
int hugetlb_report_meminfo(char *buf)
{
struct hstate *h = &default_hstate;
- return sprintf(buf,
+ int ret;
+
+ spin_lock(&hugetlb_lock);
+ ret = sprintf(buf,
"HugePages_Total: %5lu\n"
"HugePages_Free: %5lu\n"
"HugePages_Rsvd: %5lu\n"
@@ -1466,18 +1469,25 @@ int hugetlb_report_meminfo(char *buf)
h->resv_huge_pages,
h->surplus_huge_pages,
1UL << (huge_page_order(h) + PAGE_SHIFT - 10));
+ spin_unlock(&hugetlb_lock);
+ return ret;
}
int hugetlb_report_node_meminfo(int nid, char *buf)
{
struct hstate *h = &default_hstate;
- return sprintf(buf,
+ int ret;
+
+ spin_lock(&hugetlb_lock);
+ ret = sprintf(buf,
"Node %d HugePages_Total: %5u\n"
"Node %d HugePages_Free: %5u\n"
"Node %d HugePages_Surp: %5u\n",
nid, h->nr_huge_pages_node[nid],
nid, h->free_huge_pages_node[nid],
nid, h->surplus_huge_pages_node[nid]);
+ spin_unlock(&hugetlb_lock);
+ return ret;
}
/* Return the number pages of memory we physically have, in PAGE_SIZE units. */
_
Patches currently in -mm which might be from eparis@xxxxxxxxxx are
kernel-auditc-nlh-nlmsg_type-is-gotten-more-than-once.patch
hugetlb-fix-race-when-reading-proc-meminfo.patch
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