gfs2: Add GL_NOPID flag for process-independent glock holders

Add a GL_NOPID flag to indicate that once a glock holder has been acquired, it
won't be associated with the current process anymore.  This is useful for iopen
and flock glocks which are associated with open files, as well as journal glock
holders and similar which are associated with the filesystem.

Once GL_NOPID is used for all applicable glocks (see the next patches),
processes will no longer be falsely reported as holding glocks which they are
not actually holding in the glocks dump file.  Unlike before, when a process is
reported as having "(ended)", this will indicate an actual bug.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>

diff --git a/fs/gfs2/glock.c b/fs/gfs2/glock.c
index 533ec772166d047b5b23bdd5c687fc86e37aa92e..f80fba5d1d4d92945eacdccfd99c7fda6e02bed9 100644 (file)
--- a/fs/gfs2/glock.c
+++ b/fs/gfs2/glock.c
@@ -1467,6 +1467,15 @@ void gfs2_print_dbg(struct seq_file *seq, const char *fmt, ...)
        va_end(args);
 }
 
+static inline bool pid_is_meaningful(const struct gfs2_holder *gh)
+{
+        if (!(gh->gh_flags & GL_NOPID))
+                return true;
+        if (gh->gh_state == LM_ST_UNLOCKED)
+                return true;
+        return false;
+}
+
 /**
  * add_to_queue - Add a holder to the wait queue (but look for recursion)
  * @gh: the holder structure to add
@@ -1503,10 +1512,17 @@ __acquires(&gl->gl_lockref.lock)
        }
 
        list_for_each_entry(gh2, &gl->gl_holders, gh_list) {
-               if (unlikely(gh2->gh_owner_pid == gh->gh_owner_pid &&
-                   (gh->gh_gl->gl_ops->go_type != LM_TYPE_FLOCK) &&
-                   !test_bit(HIF_MAY_DEMOTE, &gh2->gh_iflags)))
-                       goto trap_recursive;
+               if (likely(gh2->gh_owner_pid != gh->gh_owner_pid))
+                       continue;
+               if (gh->gh_gl->gl_ops->go_type == LM_TYPE_FLOCK)
+                       continue;
+               if (test_bit(HIF_MAY_DEMOTE, &gh2->gh_iflags))
+                       continue;
+               if (!pid_is_meaningful(gh2))
+                       continue;
+               goto trap_recursive;
+       }
+       list_for_each_entry(gh2, &gl->gl_holders, gh_list) {
                if (try_futile &&
                    !(gh2->gh_flags & (LM_FLAG_TRY | LM_FLAG_TRY_1CB))) {
 fail:
@@ -2321,19 +2337,24 @@ static const char *hflags2str(char *buf, u16 flags, unsigned long iflags)
 static void dump_holder(struct seq_file *seq, const struct gfs2_holder *gh,
                        const char *fs_id_buf)
 {
-       struct task_struct *gh_owner = NULL;
+       const char *comm = "(none)";
+       pid_t owner_pid = 0;
        char flags_buf[32];
 
        rcu_read_lock();
-       if (gh->gh_owner_pid)
+       if (pid_is_meaningful(gh)) {
+               struct task_struct *gh_owner;
+
+               comm = "(ended)";
+               owner_pid = pid_nr(gh->gh_owner_pid);
                gh_owner = pid_task(gh->gh_owner_pid, PIDTYPE_PID);
+               if (gh_owner)
+                       comm = gh_owner->comm;
+       }
        gfs2_print_dbg(seq, "%s H: s:%s f:%s e:%d p:%ld [%s] %pS\n",
                       fs_id_buf, state2str(gh->gh_state),
                       hflags2str(flags_buf, gh->gh_flags, gh->gh_iflags),
-                      gh->gh_error,
-                      gh->gh_owner_pid ? (long)pid_nr(gh->gh_owner_pid) : -1,
-                      gh_owner ? gh_owner->comm : "(ended)",
-                      (void *)gh->gh_ip);
+                      gh->gh_error, (long)owner_pid, comm, (void *)gh->gh_ip);
        rcu_read_unlock();
 }
 

diff --git a/fs/gfs2/glock.h b/fs/gfs2/glock.h
index c0ae9100a0bcf357599a41d67a421b760eb6f11a..e764ebeba54c4f73d3fcdd9875cec6397d075b3d 100644 (file)
--- a/fs/gfs2/glock.h
+++ b/fs/gfs2/glock.h
@@ -91,6 +91,7 @@ enum {
 #define GL_ASYNC               0x0040
 #define GL_EXACT               0x0080
 #define GL_SKIP                        0x0100
+#define GL_NOPID               0x0200
 #define GL_NOCACHE             0x0400
   
 /*