5 files changed, 48 insertions, 106 deletions

diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt
index fde9fd06fa98..eaebf27539f5 100644
--- a/Documentation/filesystems/proc.txt
+++ b/Documentation/filesystems/proc.txt
@@ -356,7 +356,7 @@ address           perms offset  dev   inode      pathname
 a7cb1000-a7cb2000 ---p 00000000 00:00 0
 a7cb2000-a7eb2000 rw-p 00000000 00:00 0
 a7eb2000-a7eb3000 ---p 00000000 00:00 0
-a7eb3000-a7ed5000 rw-p 00000000 00:00 0          [stack:1001]
+a7eb3000-a7ed5000 rw-p 00000000 00:00 0
 a7ed5000-a8008000 r-xp 00000000 03:00 4222       /lib/libc.so.6
 a8008000-a800a000 r--p 00133000 03:00 4222       /lib/libc.so.6
 a800a000-a800b000 rw-p 00135000 03:00 4222       /lib/libc.so.6
@@ -388,7 +388,6 @@ is not associated with a file:
 
  [heap]                   = the heap of the program
  [stack]                  = the stack of the main process
- [stack:1001]             = the stack of the thread with tid 1001
  [vdso]                   = the "virtual dynamic shared object",
                             the kernel system call handler
 
@@ -396,10 +395,8 @@ is not associated with a file:
 
 The /proc/PID/task/TID/maps is a view of the virtual memory from the viewpoint
 of the individual tasks of a process. In this file you will see a mapping marked
-as [stack] if that task sees it as a stack. This is a key difference from the
-content of /proc/PID/maps, where you will see all mappings that are being used
-as stack by all of those tasks. Hence, for the example above, the task-level
-map, i.e. /proc/PID/task/TID/maps for thread 1001 will look like this:
+as [stack] if that task sees it as a stack. Hence, for the example above, the
+task-level map, i.e. /proc/PID/task/TID/maps for thread 1001 will look like this:
 
 08048000-08049000 r-xp 00000000 03:00 8312       /opt/test
 08049000-0804a000 rw-p 00001000 03:00 8312       /opt/test
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 4a0c31f904a6..fa95ab2d3674 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -259,23 +259,29 @@ static int do_maps_open(struct inode *inode, struct file *file,
                                 sizeof(struct proc_maps_private));
 }
 
-static pid_t pid_of_stack(struct proc_maps_private *priv,
-                                struct vm_area_struct *vma, bool is_pid)
+/*
+ * Indicate if the VMA is a stack for the given task; for
+ * /proc/PID/maps that is the stack of the main task.
+ */
+static int is_stack(struct proc_maps_private *priv,
+                    struct vm_area_struct *vma, int is_pid)
 {
-        struct inode *inode = priv->inode;
-        struct task_struct *task;
-        pid_t ret = 0;
+        int stack = 0;
+
+        if (is_pid) {
+                stack = vma->vm_start <= vma->vm_mm->start_stack &&
+                        vma->vm_end >= vma->vm_mm->start_stack;
+        } else {
+                struct inode *inode = priv->inode;
+                struct task_struct *task;
 
-        rcu_read_lock();
-        task = pid_task(proc_pid(inode), PIDTYPE_PID);
-        if (task) {
-                task = task_of_stack(task, vma, is_pid);
+                rcu_read_lock();
+                task = pid_task(proc_pid(inode), PIDTYPE_PID);
                 if (task)
-                        ret = task_pid_nr_ns(task, inode->i_sb->s_fs_info);
+                        stack = vma_is_stack_for_task(vma, task);
+                rcu_read_unlock();
         }
-        rcu_read_unlock();
-
-        return ret;
+        return stack;
 }
 
 static void
@@ -335,8 +341,6 @@ show_map_vma(struct seq_file *m, struct vm_area_struct *vma, int is_pid)
 
         name = arch_vma_name(vma);
         if (!name) {
-                pid_t tid;
-
                 if (!mm) {
                         name = "[vdso]";
                         goto done;
@@ -348,21 +352,8 @@ show_map_vma(struct seq_file *m, struct vm_area_struct *vma, int is_pid)
                         goto done;
                 }
 
-                tid = pid_of_stack(priv, vma, is_pid);
-                if (tid != 0) {
-                        /*
-                         * Thread stack in /proc/PID/task/TID/maps or
-                         * the main process stack.
-                         */
-                        if (!is_pid || (vma->vm_start <= mm->start_stack &&
-                            vma->vm_end >= mm->start_stack)) {
-                                name = "[stack]";
-                        } else {
-                                /* Thread stack in /proc/PID/maps */
-                                seq_pad(m, ' ');
-                                seq_printf(m, "[stack:%d]", tid);
-                        }
-                }
+                if (is_stack(priv, vma, is_pid))
+                        name = "[stack]";
         }
 
 done:
@@ -1618,19 +1609,8 @@ static int show_numa_map(struct seq_file *m, void *v, int is_pid)
                 seq_file_path(m, file, "\n\t= ");
         } else if (vma->vm_start <= mm->brk && vma->vm_end >= mm->start_brk) {
                 seq_puts(m, " heap");
-        } else {
-                pid_t tid = pid_of_stack(proc_priv, vma, is_pid);
-                if (tid != 0) {
-                        /*
-                         * Thread stack in /proc/PID/task/TID/maps or
-                         * the main process stack.
-                         */
-                        if (!is_pid || (vma->vm_start <= mm->start_stack &&
-                            vma->vm_end >= mm->start_stack))
-                                seq_puts(m, " stack");
-                        else
-                                seq_printf(m, " stack:%d", tid);
-                }
+        } else if (is_stack(proc_priv, vma, is_pid)) {
+                seq_puts(m, " stack");
         }
 
         if (is_vm_hugetlb_page(vma))
diff --git a/fs/proc/task_nommu.c b/fs/proc/task_nommu.c
index e0d64c92e4f6..faacb0c0d857 100644
--- a/fs/proc/task_nommu.c
+++ b/fs/proc/task_nommu.c
@@ -123,23 +123,26 @@ unsigned long task_statm(struct mm_struct *mm,
         return size;
 }
 
-static pid_t pid_of_stack(struct proc_maps_private *priv,
-                                struct vm_area_struct *vma, bool is_pid)
+static int is_stack(struct proc_maps_private *priv,
+                    struct vm_area_struct *vma, int is_pid)
 {
-        struct inode *inode = priv->inode;
-        struct task_struct *task;
-        pid_t ret = 0;
-
-        rcu_read_lock();
-        task = pid_task(proc_pid(inode), PIDTYPE_PID);
-        if (task) {
-                task = task_of_stack(task, vma, is_pid);
+        struct mm_struct *mm = vma->vm_mm;
+        int stack = 0;
+
+        if (is_pid) {
+                stack = vma->vm_start <= mm->start_stack &&
+                        vma->vm_end >= mm->start_stack;
+        } else {
+                struct inode *inode = priv->inode;
+                struct task_struct *task;
+
+                rcu_read_lock();
+                task = pid_task(proc_pid(inode), PIDTYPE_PID);
                 if (task)
-                        ret = task_pid_nr_ns(task, inode->i_sb->s_fs_info);
+                        stack = vma_is_stack_for_task(vma, task);
+                rcu_read_unlock();
         }
-        rcu_read_unlock();
-
-        return ret;
+        return stack;
 }
 
 /*
@@ -181,21 +184,9 @@ static int nommu_vma_show(struct seq_file *m, struct vm_area_struct *vma,
         if (file) {
                 seq_pad(m, ' ');
                 seq_file_path(m, file, "");
-        } else if (mm) {
-                pid_t tid = pid_of_stack(priv, vma, is_pid);
-
-                if (tid != 0) {
-                        seq_pad(m, ' ');
-                        /*
-                         * Thread stack in /proc/PID/task/TID/maps or
-                         * the main process stack.
-                         */
-                        if (!is_pid || (vma->vm_start <= mm->start_stack &&
-                            vma->vm_end >= mm->start_stack))
-                                seq_printf(m, "[stack]");
-                        else
-                                seq_printf(m, "[stack:%d]", tid);
-                }
+        } else if (mm && is_stack(priv, vma, is_pid)) {
+                seq_pad(m, ' ');
+                seq_printf(m, "[stack]");
         }
 
         seq_putc(m, '\n');
diff --git a/include/linux/mm.h b/include/linux/mm.h
index f1cd22f2df1a..0b50d7848e3a 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1341,8 +1341,7 @@ static inline int stack_guard_page_end(struct vm_area_struct *vma,
                 !vma_growsup(vma->vm_next, addr);
 }
 
-extern struct task_struct *task_of_stack(struct task_struct *task,
-                                struct vm_area_struct *vma, bool in_group);
+int vma_is_stack_for_task(struct vm_area_struct *vma, struct task_struct *t);
 
 extern unsigned long move_page_tables(struct vm_area_struct *vma,
                 unsigned long old_addr, struct vm_area_struct *new_vma,
diff --git a/mm/util.c b/mm/util.c
index c108a6542d05..4fb14ca5a419 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -230,36 +230,11 @@ void __vma_link_list(struct mm_struct *mm, struct vm_area_struct *vma,
 }
 
 /* Check if the vma is being used as a stack by this task */
-static int vm_is_stack_for_task(struct task_struct *t,
-                                struct vm_area_struct *vma)
+int vma_is_stack_for_task(struct vm_area_struct *vma, struct task_struct *t)
 {
         return (vma->vm_start <= KSTK_ESP(t) && vma->vm_end >= KSTK_ESP(t));
 }
 
-/*
- * Check if the vma is being used as a stack.
- * If is_group is non-zero, check in the entire thread group or else
- * just check in the current task. Returns the task_struct of the task
- * that the vma is stack for. Must be called under rcu_read_lock().
- */
-struct task_struct *task_of_stack(struct task_struct *task,
-                                struct vm_area_struct *vma, bool in_group)
-{
-        if (vm_is_stack_for_task(task, vma))
-                return task;
-
-        if (in_group) {
-                struct task_struct *t;
-
-                for_each_thread(task, t) {
-                        if (vm_is_stack_for_task(t, vma))
-                                return t;
-                }
-        }
-
-        return NULL;
-}
-
 #if defined(CONFIG_MMU) && !defined(HAVE_ARCH_PICK_MMAP_LAYOUT)
 void arch_pick_mmap_layout(struct mm_struct *mm)
 {