fs/proc/task_mmu.c: kill the suboptimal and confusing m->version logic

m_start() carefully documents, checks, and sets "m->version = -1" if
we are going to return NULL. The only problem is that we will be never
called again if m_start() returns NULL, so this is simply pointless
and misleading.

Otoh, ->show() methods m->version = 0 if vma == tail_vma and this is
just wrong, we want -1 in this case. And in fact we also want -1 if
->vm_next == NULL and ->tail_vma == NULL.

And it is not used consistently, the "scan vmas" loop in m_start()
should update last_addr too.

Finally, imo the whole "last_addr" logic in m_start() looks horrible.
find_vma(last_addr) is called unconditionally even if we are not going
to use the result. But the main problem is that this code participates
in tail_vma-or-NULL mess, and this looks simply unfixable.

Remove this optimization. We will add it back after some cleanups.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 30aa2dd3e6f54a1f9e34c3b87c75a368f43c5e4a..e182fc51ec2bfbe318e04524502124e409cf1d70 100644 (file)
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -141,20 +141,10 @@ static void vma_stop(struct proc_maps_private *priv)
 static void *m_start(struct seq_file *m, loff_t *pos)
 {
        struct proc_maps_private *priv = m->private;
-       unsigned long last_addr = m->version;
        struct mm_struct *mm;
        struct vm_area_struct *vma, *tail_vma = NULL;
        loff_t l = *pos;
 
-       /*
-        * We remember last_addr rather than next_addr to hit with
-        * vmacache most of the time. We have zero last_addr at
-        * the beginning and also after lseek. We will have -1 last_addr
-        * after the end of the vmas.
-        */
-       if (last_addr == -1UL)
-               return NULL;
-
        priv->task = get_pid_task(priv->pid, PIDTYPE_PID);
        if (!priv->task)
                return ERR_PTR(-ESRCH);
@@ -167,12 +157,6 @@ static void *m_start(struct seq_file *m, loff_t *pos)
        tail_vma = get_gate_vma(mm);
        priv->tail_vma = tail_vma;
        hold_task_mempolicy(priv);
-       /* Start with last addr hint */
-       vma = find_vma(mm, last_addr);
-       if (last_addr && vma) {
-               vma = vma->vm_next;
-               goto out;
-       }
 
        /*
         * Check the vma index is within the range and do
@@ -193,8 +177,6 @@ out:
        if (vma)
                return vma;
 
-       /* End of vmas has been reached */
-       m->version = (tail_vma != NULL)? 0: -1UL;
        if (tail_vma)
                return tail_vma;
 
@@ -366,14 +348,7 @@ done:
 
 static int show_map(struct seq_file *m, void *v, int is_pid)
 {
-       struct vm_area_struct *vma = v;
-       struct proc_maps_private *priv = m->private;
-
-       show_map_vma(m, vma, is_pid);
-
-       if (m->count < m->size)  /* vma is copied successfully */
-               m->version = (vma != priv->tail_vma)
-                       ? vma->vm_start : 0;
+       show_map_vma(m, v, is_pid);
        return 0;
 }
 
@@ -599,7 +574,6 @@ static void show_smap_vma_flags(struct seq_file *m, struct vm_area_struct *vma)
 
 static int show_smap(struct seq_file *m, void *v, int is_pid)
 {
-       struct proc_maps_private *priv = m->private;
        struct vm_area_struct *vma = v;
        struct mem_size_stats mss;
        struct mm_walk smaps_walk = {
@@ -652,10 +626,6 @@ static int show_smap(struct seq_file *m, void *v, int is_pid)
                                mss.nonlinear >> 10);
 
        show_smap_vma_flags(m, vma);
-
-       if (m->count < m->size)  /* vma is copied successfully */
-               m->version = (vma != priv->tail_vma)
-                       ? vma->vm_start : 0;
        return 0;
 }
 
@@ -1510,9 +1480,6 @@ static int show_numa_map(struct seq_file *m, void *v, int is_pid)
                        seq_printf(m, " N%d=%lu", nid, md->node[nid]);
 out:
        seq_putc(m, '\n');
-
-       if (m->count < m->size)
-               m->version = (vma != proc_priv->tail_vma) ? vma->vm_start : 0;
        return 0;
 }