Update compaction instrumentation to 3.16 kernel

[lttng-modules.git] / lttng-statedump-impl.c

diff --git a/lttng-statedump-impl.c b/lttng-statedump-impl.c
index d0e641a97ca70452508ccf618ebf9c594b67cb5b..17b02faf2be564385ff3c2bd5b7a210ef77988d8 100644 (file)
--- a/lttng-statedump-impl.c
+++ b/lttng-statedump-impl.c
@@ -79,7 +79,7 @@ struct lttng_fd_ctx {
        char *page;
        struct lttng_session *session;
        struct task_struct *p;
-       struct fdtable *fdt;
+       struct files_struct *files;
 };
 
 /*
@@ -213,19 +213,42 @@ int lttng_enumerate_network_ip_interface(struct lttng_session *session)
 }
 #endif /* CONFIG_INET */
 
+#ifdef FD_ISSET        /* For old kernels lacking close_on_exec() */
+static inline bool lttng_close_on_exec(int fd, const struct fdtable *fdt)
+{
+       return FD_ISSET(fd, fdt->close_on_exec);
+}
+#else
+static inline bool lttng_close_on_exec(int fd, const struct fdtable *fdt)
+{
+       return close_on_exec(fd, fdt);
+}
+#endif
+
 static
 int lttng_dump_one_fd(const void *p, struct file *file, unsigned int fd)
 {
        const struct lttng_fd_ctx *ctx = p;
        const char *s = d_path(&file->f_path, ctx->page, PAGE_SIZE);
        unsigned int flags = file->f_flags;
+       struct fdtable *fdt;
 
        /*
         * We don't expose kernel internal flags, only userspace-visible
         * flags.
         */
        flags &= ~FMODE_NONOTIFY;
-       if (test_bit(fd, ctx->fdt->close_on_exec))
+       fdt = files_fdtable(ctx->files);
+       /*
+        * We need to check here again whether fd is within the fdt
+        * max_fds range, because we might be seeing a different
+        * files_fdtable() than iterate_fd(), assuming only RCU is
+        * protecting the read. In reality, iterate_fd() holds
+        * file_lock, which should ensure the fdt does not change while
+        * the lock is taken, but we are not aware whether this is
+        * guaranteed or not, so play safe.
+        */
+       if (fd < fdt->max_fds && lttng_close_on_exec(fd, fdt))
                flags |= O_CLOEXEC;
        if (IS_ERR(s)) {
                struct dentry *dentry = file->f_path.dentry;
@@ -248,10 +271,15 @@ void lttng_enumerate_task_fd(struct lttng_session *session,
                struct task_struct *p, char *tmp)
 {
        struct lttng_fd_ctx ctx = { .page = tmp, .session = session, .p = p };
+       struct files_struct *files;
 
        task_lock(p);
-       ctx.fdt = files_fdtable(p->files);
-       lttng_iterate_fd(p->files, 0, lttng_dump_one_fd, &ctx);
+       files = p->files;
+       if (!files)
+               goto end;
+       ctx.files = files;
+       lttng_iterate_fd(files, 0, lttng_dump_one_fd, &ctx);
+end:
        task_unlock(p);
 }