blktrace: break mlock in case of is_done.

In 38-rc2, there is a bug in mlock which will return
error in mlock of blktrace(I have sent the corresponding
patch to the lkml). So when we try to break the blktrace
by "ctrl+c", mlock will loop forever and in the end, I
have to use "kill -9" to kill it and then run "blktrace -k"
to stop the tracer. I don't think it is good.

How to reproduce it is simple:
Use a 38-rc kernel, and run
blktrace /dev/sdx
then use "ctrl+c", it doesn't exit.

So this patch adds the check for tp->is_done. In
case of is_done is set, break mlock so that we don't
deadloop in the mlock. In case of the real mlock error,
I will let it to retry 10 times and it should succeed
after 10 tries in case of tp->is_done. If tp isn't set
or tp->is_done isn't set, it works like the original
design.

Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Tao Ma <boyu.mt@taobao.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

diff --git a/blktrace.c b/blktrace.c
index 4cccb7c635f720c89bd3b13696c1e339af31b1bf..a2bffa2d11e39337ca9873da4f3bb2467ae3ac76 100644 (file)
--- a/blktrace.c
+++ b/blktrace.c
@@ -721,18 +721,24 @@ static void *my_mmap(void *addr, size_t length, int prot, int flags, int fd,
        return new;
 }
 
-static int my_mlock(const void *addr, size_t len)
+static int my_mlock(struct tracer *tp,
+                   const void *addr, size_t len)
 {
-       int ret;
+       int ret, retry = 0;
 
        do {
                ret = mlock(addr, len);
+               if ((retry >= 10) && tp && tp->is_done)
+                       break;
+               retry++;
        } while (ret < 0 && handle_mem_failure(len));
 
        return ret;
 }
 
-static int setup_mmap(int fd, unsigned int maxlen, struct mmap_info *mip)
+static int setup_mmap(int fd, unsigned int maxlen,
+                     struct mmap_info *mip,
+                     struct tracer *tp)
 {
        if (mip->fs_off + maxlen > mip->fs_buf_len) {
                unsigned long nr = max(16, mip->buf_nr);
@@ -759,7 +765,10 @@ static int setup_mmap(int fd, unsigned int maxlen, struct mmap_info *mip)
                        perror("setup_mmap: mmap");
                        return 1;
                }
-               my_mlock(mip->fs_buf, mip->fs_buf_len);
+               if (my_mlock(tp, mip->fs_buf, mip->fs_buf_len) < 0) {
+                       perror("setup_mlock: mlock");
+                       return 1;
+               }
        }
 
        return 0;
@@ -1683,7 +1692,7 @@ static int handle_pfds_file(struct tracer *tp, int nevs, int force_read)
                if (pfd->revents & POLLIN || force_read) {
                        mip = &iop->mmap_info;
 
-                       ret = setup_mmap(iop->ofd, buf_size, mip);
+                       ret = setup_mmap(iop->ofd, buf_size, mip, tp);
                        if (ret < 0) {
                                pfd->events = 0;
                                break;
@@ -2381,7 +2390,7 @@ static void net_client_read_data(struct cl_conn *nc, struct devpath *dpp,
        struct io_info *iop = &dpp->ios[bnh->cpu];
        struct mmap_info *mip = &iop->mmap_info;
 
-       if (setup_mmap(iop->ofd, bnh->len, &iop->mmap_info)) {
+       if (setup_mmap(iop->ofd, bnh->len, &iop->mmap_info, NULL)) {
                fprintf(stderr, "ncd(%s:%d): mmap failed\n",
                        nc->ch->hostname, nc->fd);
                exit(1);