Gitweb: http://git.fedorahosted.org/git/?p=lvm2.git;a=commitdiff;h=cf37c04347c6b6209... Commit: cf37c04347c6b6209420764da43127a96445af0e Parent: 542b03ee007d50cd8aa6dbd582b79369a38919b0 Author: Petr Rockai prockai@redhat.com AuthorDate: Tue Sep 30 10:56:59 2014 +0200 Committer: Petr Rockai prockai@redhat.com CommitterDate: Tue Nov 18 03:17:27 2014 +0100
memlock: Make malloc reserve more robust against glibc tricks.
--- lib/mm/memlock.c | 48 ++++++++++++++++++++++++++++++++++++++++++++---- 1 files changed, 44 insertions(+), 4 deletions(-)
diff --git a/lib/mm/memlock.c b/lib/mm/memlock.c index 547fb46..e771075 100644 --- a/lib/mm/memlock.c +++ b/lib/mm/memlock.c @@ -25,6 +25,7 @@ #include <sys/mman.h> #include <sys/time.h> #include <sys/resource.h> +#include <malloc.h>
#ifndef DEVMAPPER_SUPPORT
@@ -133,9 +134,11 @@ static void _touch_memory(void *mem, size_t size) static void _allocate_memory(void) { #ifndef VALGRIND_POOL - /* With Valgrind don't waste time in with preallocating memory */ void *stack_mem, *temp_malloc_mem; struct rlimit limit; + int i, area = 0, missing = _size_malloc_tmp, max_areas = 32, hblks; + char *areas[max_areas]; +
/* Check if we could preallocate requested stack */ if ((getrlimit (RLIMIT_STACK, &limit) == 0) && @@ -144,13 +147,50 @@ static void _allocate_memory(void) _touch_memory(stack_mem, _size_stack); /* FIXME else warn user setting got ignored */
- if ((temp_malloc_mem = malloc(_size_malloc_tmp))) - _touch_memory(temp_malloc_mem, _size_malloc_tmp); + /* + * When a brk() fails due to fragmented address space (which sometimes + * happens when we try to grab 8M or so), glibc will make a new + * arena. In this arena, the rules for using “direct” mmap are relaxed, + * circumventing the MAX_MMAPs and MMAP_THRESHOLD settings. We can, + * however, detect when this happens with mallinfo() and try to co-opt + * malloc into using MMAP as a MORECORE substitute instead of returning + * MMAP'd memory directly. Since MMAP-as-MORECORE does not munmap the + * memory on free(), this is good enough for our purposes. + */ + while (missing > 0) { + struct mallinfo inf = mallinfo(); + hblks = inf.hblks; + + if ((areas[area] = malloc(_size_malloc_tmp))) + _touch_memory(areas[area], _size_malloc_tmp); + + inf = mallinfo(); + + if (hblks < inf.hblks) { + /* malloc cheated and used mmap, even though we told it + not to; we try with twice as many areas, each half + the size, to circumvent the faulty logic in glibc */ + free(areas[area]); + _size_malloc_tmp /= 2; + } else { + ++ area; + missing -= _size_malloc_tmp; + } + + if (area == max_areas && missing > 0) { + /* Too bad. Warn the user and proceed, as things are + * most likely going to work out anyway. */ + log_warn("WARNING: Failed to reserve memory, %d bytes missing.", missing); + break; + } + }
if ((_malloc_mem = malloc(_size_malloc))) _touch_memory(_malloc_mem, _size_malloc);
- free(temp_malloc_mem); + /* free up the reserves so subsequent malloc's can use that memory */ + for (i = 0; i < area; ++i) + free(areas[i]); #endif }
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