[Dazuko-devel] Patch 4/5

[Lino Sanfilippo]

This patch fixes a missing cleanup in cases where an error occurs
after an event has already been assigned to a group.
Before an event has not been put back to the "todo" list properly
(the list_del() for the working list was missing) and also was not
put back in cases of error in dazukofs_group_read().

There is still something missing:
If a filedescriptor has already been opened for an event, it has to
be closed before it is put back to the "working list".
I will send a fix for this issue with another patch.


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diff -Nurp dazukofs-3.1.3-patch3/event.c dazukofs-3.1.3-patch4/event.c
--- dazukofs-3.1.3-patch3/event.c       2010-07-06 17:28:05.000000000 +0200
+++ dazukofs-3.1.3-patch4/event.c       2010-07-08 18:10:41.000000000 +0200
@@ -28,50 +28,17 @@
 #include <linux/pid.h>
 #include <linux/slab.h>
 
+#include "event.h"
 #include "dev.h"
 #include "dazukofs_fs.h"
 
 struct dazukofs_proc {
-       struct list_head list;
+       struct list_head list; 
        struct pid *proc_id;
        int within_list;
 };
 
-struct dazukofs_event {
-       unsigned long event_id;
-       struct dentry *dentry;
-       struct vfsmount *mnt;
-       struct pid *proc_id;
-       wait_queue_head_t queue;
-
-       /* protects: deny, deprecated, assigned */
-       struct mutex assigned_mutex;
-
-       int deny;
-       int deprecated;
-       int assigned;
-};
 
-struct dazukofs_event_container {
-       struct list_head list;
-       struct dazukofs_event *event;
-       struct file *file;
-       int fd;
-};
-
-struct dazukofs_group {
-       struct list_head list;
-       char *name;
-       size_t name_length;
-       unsigned long group_id;
-       struct dazukofs_event_container todo_list;
-       wait_queue_head_t queue;
-       struct dazukofs_event_container working_list;
-       atomic_t use_count;
-       int tracking;
-       int track_count;
-       int deprecated;
-};
 
 static struct dazukofs_group group_list;
 static int group_count;
@@ -899,6 +866,15 @@ out:
        return ret;
 }
 
+
+void set_event_pending(struct dazukofs_group *grp,
+                       struct dazukofs_event_container *ec)
+{
+       mutex_lock(&work_mutex);
+       list_add(&ec->list, &grp->working_list.list);
+       mutex_unlock(&work_mutex);
+}
+
 /**
  * unclaim_event - return an event to the todo list
  * @grp: group to which the event is assigned
@@ -907,7 +883,7 @@ out:
  * Description: This function puts the given event container on the todo
  * list and wake the group.
  */
-static void unclaim_event(struct dazukofs_group *grp,
+void unclaim_event(struct dazukofs_group *grp,
                          struct dazukofs_event_container *ec)
 {
        /* put the event on the todo list */
@@ -938,7 +914,6 @@ static struct dazukofs_event_container *
                ec = list_first_entry(&grp->todo_list.list,
                                      struct dazukofs_event_container, list);
                list_del(&ec->list);
-               list_add(&ec->list, &grp->working_list.list);
        }
        mutex_unlock(&work_mutex);
 
@@ -1034,7 +1009,6 @@ static int is_event_available(struct daz
        return ret;
 }
 
-/**
  * dazukofs_get_event - get an event to process
  * @group_id: id of the group we belong to
  * @event_id: to be filled in with the new event id
@@ -1047,8 +1021,8 @@ static int is_event_available(struct daz
  *
  * Returns 0 on success.
  */
-int dazukofs_get_event(unsigned long group_id, unsigned long *event_id,
-                      int *fd, pid_t *pid)
+int dazukofs_get_event(unsigned long group_id, struct dazukofs_group **pgrp,
+                       struct dazukofs_event_container **pec) 
 {
        struct dazukofs_group *grp = NULL;
        struct dazukofs_event_container *ec;
@@ -1067,10 +1041,8 @@ int dazukofs_get_event(unsigned long gro
        }
        mutex_unlock(&work_mutex);
 
-       if (!found) {
-               ret = -EFAULT;
-               goto out;
-       }
+       if (!found) 
+               return -EINVAL;
 
        while (1) {
                ret = wait_event_freezable(grp->queue,
@@ -1087,14 +1059,9 @@ int dazukofs_get_event(unsigned long gro
                ec = claim_event(grp);
                if (ec) {
                        ret = open_file(ec);
-                       if (ret == 0) {
-                               *event_id = ec->event->event_id;
-                               *fd = ec->fd;
-
-                               /* set to 0 if not within namespace */
-                               *pid = pid_vnr(ec->event->proc_id);
+                       if (ret == 0) 
                                break;
-                       } else {
+                       else {
                                unclaim_event(grp, ec);
                                if (ret == -ENFILE) {
                                        /* The registered process may not open
@@ -1103,8 +1070,16 @@ int dazukofs_get_event(unsigned long gro
                                }
                        }
                }
+               /* we did not get the event */
+               atomic_dec(&grp->use_count);
        }
-       atomic_dec(&grp->use_count);
-out:
-       return ret;
+
+       if (ret) {
+               atomic_dec(&grp->use_count);
+               return ret;
+       }
+
+       *pgrp = grp;
+       *pec = ec;
+       return 0;
 }
diff -Nurp dazukofs-3.1.3-patch3/event.h dazukofs-3.1.3-patch4/event.h
--- dazukofs-3.1.3-patch3/event.h       2010-07-06 17:28:05.000000000 +0200
+++ dazukofs-3.1.3-patch4/event.h       2010-07-08 16:39:46.000000000 +0200
@@ -21,11 +21,56 @@
 #ifndef __EVENT_H
 #define __EVENT_H
 
+#include <linux/list.h>
+#include <linux/wait.h>
+
+
+struct dazukofs_event {
+       unsigned long event_id;
+       struct dentry *dentry;
+       struct vfsmount *mnt;
+       struct pid *proc_id;
+       wait_queue_head_t queue;
+
+       /* protects: deny, deprecated, assigned */
+       struct mutex assigned_mutex;
+
+       int deny;
+       int deprecated;
+       int assigned;
+};
+
+struct dazukofs_event_container {
+       struct list_head list;
+       struct dazukofs_event *event;
+       struct file *file;
+       int fd;
+};
+
+struct dazukofs_group {
+       struct list_head list;
+       char *name;
+       size_t name_length;
+       unsigned long group_id;
+       struct dazukofs_event_container todo_list;
+       wait_queue_head_t queue;
+       struct dazukofs_event_container working_list;
+       atomic_t use_count;
+       int tracking;
+       int track_count;
+       int deprecated;
+};
+
 extern int dazukofs_init_events(void);
 extern void dazukofs_destroy_events(void);
 
-extern int dazukofs_get_event(unsigned long group_id,
-                             unsigned long *event_id, int *fd, pid_t *pid);
+extern void set_event_pending(struct dazukofs_group *grp,
+                       struct dazukofs_event_container *ec);
+extern void unclaim_event(struct dazukofs_group *grp, 
+                          struct dazukofs_event_container *ec);
+extern int dazukofs_get_event(unsigned long group_id, 
+                              struct dazukofs_group **pgrp, 
+                             struct dazukofs_event_container **pec); 
 extern int dazukofs_return_event(unsigned long group_id,
                                 unsigned long event_id, int deny);
 
diff -Nurp dazukofs-3.1.3-patch3/group_dev.c dazukofs-3.1.3-patch4/group_dev.c
--- dazukofs-3.1.3-patch3/group_dev.c   2010-07-06 17:40:52.000000000 +0200
+++ dazukofs-3.1.3-patch4/group_dev.c   2010-07-08 15:30:19.000000000 +0200
@@ -58,33 +58,41 @@ static ssize_t dazukofs_group_read(int g
 {
 #define DAZUKOFS_MIN_READ_BUFFER 43
        char tmp[DAZUKOFS_MIN_READ_BUFFER];
-       ssize_t tmp_used;
-       pid_t pid;
-       int fd;
-       int err;
-       unsigned long event_id;
+       struct dazukofs_event_container *ec;
+       struct dazukofs_group *grp;
+       ssize_t rv;
 
 
        if (length < DAZUKOFS_MIN_READ_BUFFER)
                return -EINVAL;
 
-       err = dazukofs_get_event(group_id, &event_id, &fd, &pid);
-       if (err) {
+       rv = dazukofs_get_event(group_id, &grp, &ec);
+       if (rv) {
                /* convert some errors to acceptable read(2) errno values */
-               if (err == -ENFILE)
-                       return -EIO;
-               return err;
+               if (rv == -ENFILE)
+                       rv = -EIO;
+               return rv;
        }
 
-       tmp_used = snprintf(tmp, sizeof(tmp)-1, "id=%lu\nfd=%d\npid=%d\n",
-                           event_id, fd, pid);
-       if (tmp_used >= sizeof(tmp))
-               return -EINVAL;
+       rv = snprintf(tmp, sizeof(tmp)-1, "id=%lu\nfd=%d\npid=%d\n",
+                           ec->event->event_id, ec->fd, 
+                           pid_vnr(ec->event->proc_id));
+       if (rv >= sizeof(tmp)) {
+               unclaim_event(grp, ec);
+               rv = -EINVAL;
+               goto err;
+       }
 
-       if (copy_to_user(buffer, tmp, tmp_used))
-               return -EFAULT;
+       if (copy_to_user(buffer, tmp, rv)) {
+               unclaim_event(grp, ec);
+               rv = -EFAULT;
+               goto err;
+       }
+       set_event_pending(grp, ec);
 
-       return tmp_used;
+err:
+       atomic_dec(&grp->use_count);
+       return rv;
 }
 
 static ssize_t dazukofs_group_write(int group_id, struct file *file,