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authorKonstantin Khlebnikov <koct9i@gmail.com>2014-06-04 16:05:30 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2014-06-04 16:53:51 -0700
commit1d46598b7903cd5ec83c49adbd741f43bb0ffcdc (patch)
tree162df1711beca7f301a0c1d8b1967dde7012e72c
parentd27050641e9bc056446deb0814e7ba1aa7911f5a (diff)
tools/vm/page-types.c: catch sigbus if raced with truncate
Recently added page-cache dumping is known to be a little bit racy. But after race with truncate it just dies due to unhandled SIGBUS when it tries to poke pages beyond the new end of file. This patch adds handler for SIGBUS which skips the rest of the file. Signed-off-by: Konstantin Khlebnikov <koct9i@gmail.com> Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--tools/vm/page-types.c35
1 files changed, 32 insertions, 3 deletions
diff --git a/tools/vm/page-types.c b/tools/vm/page-types.c
index 05654f5e48d5..c4d6d2e20e0d 100644
--- a/tools/vm/page-types.c
+++ b/tools/vm/page-types.c
@@ -32,6 +32,8 @@
#include <assert.h>
#include <ftw.h>
#include <time.h>
+#include <setjmp.h>
+#include <signal.h>
#include <sys/types.h>
#include <sys/errno.h>
#include <sys/fcntl.h>
@@ -824,21 +826,38 @@ static void show_file(const char *name, const struct stat *st)
atime, now - st->st_atime);
}
+static sigjmp_buf sigbus_jmp;
+
+static void * volatile sigbus_addr;
+
+static void sigbus_handler(int sig, siginfo_t *info, void *ucontex)
+{
+ (void)sig;
+ (void)ucontex;
+ sigbus_addr = info ? info->si_addr : NULL;
+ siglongjmp(sigbus_jmp, 1);
+}
+
+static struct sigaction sigbus_action = {
+ .sa_sigaction = sigbus_handler,
+ .sa_flags = SA_SIGINFO,
+};
+
static void walk_file(const char *name, const struct stat *st)
{
uint8_t vec[PAGEMAP_BATCH];
uint64_t buf[PAGEMAP_BATCH], flags;
unsigned long nr_pages, pfn, i;
+ off_t off, end = st->st_size;
int fd;
- off_t off;
ssize_t len;
void *ptr;
int first = 1;
fd = checked_open(name, O_RDONLY|O_NOATIME|O_NOFOLLOW);
- for (off = 0; off < st->st_size; off += len) {
- nr_pages = (st->st_size - off + page_size - 1) / page_size;
+ for (off = 0; off < end; off += len) {
+ nr_pages = (end - off + page_size - 1) / page_size;
if (nr_pages > PAGEMAP_BATCH)
nr_pages = PAGEMAP_BATCH;
len = nr_pages * page_size;
@@ -855,11 +874,19 @@ static void walk_file(const char *name, const struct stat *st)
if (madvise(ptr, len, MADV_RANDOM))
fatal("madvice failed: %s", name);
+ if (sigsetjmp(sigbus_jmp, 1)) {
+ end = off + sigbus_addr ? sigbus_addr - ptr : 0;
+ fprintf(stderr, "got sigbus at offset %lld: %s\n",
+ (long long)end, name);
+ goto got_sigbus;
+ }
+
/* populate ptes */
for (i = 0; i < nr_pages ; i++) {
if (vec[i] & 1)
(void)*(volatile int *)(ptr + i * page_size);
}
+got_sigbus:
/* turn off harvesting reference bits */
if (madvise(ptr, len, MADV_SEQUENTIAL))
@@ -910,6 +937,7 @@ static void walk_page_cache(void)
kpageflags_fd = checked_open(PROC_KPAGEFLAGS, O_RDONLY);
pagemap_fd = checked_open("/proc/self/pagemap", O_RDONLY);
+ sigaction(SIGBUS, &sigbus_action, NULL);
if (stat(opt_file, &st))
fatal("stat failed: %s\n", opt_file);
@@ -925,6 +953,7 @@ static void walk_page_cache(void)
close(kpageflags_fd);
close(pagemap_fd);
+ signal(SIGBUS, SIG_DFL);
}
static void parse_file(const char *name)