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Subject[PATCH] Problem with smaps in 2.6.13-rc4-mm1
Date
On Saturday 06 August 2005 09:15, Torsten Foertsch wrote:
> when trying out smaps I have encountered the following problem:
> > cat /proc/$P/smaps | diff - /proc/$P/smaps
>
> 239,241c239,241
> < bfbaf000-bfbc4000 rw-p bfbaf000 00:00 0 [stack]
> < Size: 84 kB
> < Rss: 24 kB
> ---
>
> > b7fc4000-b7fc6000 rwxp 00015000 08:02 12558 /lib/ld-2.3.4.so
> > Size: 8 kB
> > Rss: 8 kB
>
> 245c245
> < Private_Dirty: 24 kB
> ---
>
> > Private_Dirty: 8 kB

The problem occures because show_smap calls first show_map and then prints its
additional information to the seq_file. show_map checks if all it has to
print fits into the buffer and if yes marks the current vma as written. While
that is correct for show_map it is not for show_smap. Here the vma should be
marked as written only after the additional information is also written.

The attached patch cures the problem. It moves the functionality of the
show_map function to a new function show_map_internal that is called with an
additional struct mem_size_stats* argument. Then show_map calls
show_map_internal with NULL as struct mem_size_stats* whereas show_smap calls
it with a real pointer. Now the final

if (m->count < m->size) /* vma is copied successfully */
m->version = (vma != get_gate_vma(task))? vma->vm_start: 0;

is done only if the whole entry fits into the buffer.

Torsten
--- linux-2.6.13-rc4-mm1/fs/proc/task_mmu.c~ 2005-08-03 12:48:35.000000000 +0200
+++ linux-2.6.13-rc4-mm1/fs/proc/task_mmu.c 2005-08-06 18:43:11.160005664 +0200
@@ -92,7 +92,16 @@
seq_printf(m, "%*c", len, ' ');
}

-static int show_map(struct seq_file *m, void *v)
+struct mem_size_stats
+{
+ unsigned long resident;
+ unsigned long shared_clean;
+ unsigned long shared_dirty;
+ unsigned long private_clean;
+ unsigned long private_dirty;
+};
+
+static int show_map_internal(struct seq_file *m, void *v, struct mem_size_stats *mss)
{
struct task_struct *task = m->private;
struct vm_area_struct *vma = v;
@@ -146,19 +155,31 @@
}
}
seq_putc(m, '\n');
+
+ if (mss)
+ seq_printf(m,
+ "Size: %8lu kB\n"
+ "Rss: %8lu kB\n"
+ "Shared_Clean: %8lu kB\n"
+ "Shared_Dirty: %8lu kB\n"
+ "Private_Clean: %8lu kB\n"
+ "Private_Dirty: %8lu kB\n",
+ (vma->vm_end - vma->vm_start) >> 10,
+ mss->resident >> 10,
+ mss->shared_clean >> 10,
+ mss->shared_dirty >> 10,
+ mss->private_clean >> 10,
+ mss->private_dirty >> 10);
+
if (m->count < m->size) /* vma is copied successfully */
m->version = (vma != get_gate_vma(task))? vma->vm_start: 0;
return 0;
}

-struct mem_size_stats
+static int show_map(struct seq_file *m, void *v)
{
- unsigned long resident;
- unsigned long shared_clean;
- unsigned long shared_dirty;
- unsigned long private_clean;
- unsigned long private_dirty;
-};
+ return show_map_internal(m, v, 0);
+}

static void smaps_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
unsigned long addr, unsigned long end,
@@ -248,33 +269,17 @@
{
struct vm_area_struct *vma = v;
struct mm_struct *mm = vma->vm_mm;
- unsigned long vma_len = (vma->vm_end - vma->vm_start);
struct mem_size_stats mss;

memset(&mss, 0, sizeof mss);

- show_map(m, v);
-
if (mm) {
spin_lock(&mm->page_table_lock);
smaps_pgd_range(vma, vma->vm_start, vma->vm_end, &mss);
spin_unlock(&mm->page_table_lock);
}

- seq_printf(m,
- "Size: %8lu kB\n"
- "Rss: %8lu kB\n"
- "Shared_Clean: %8lu kB\n"
- "Shared_Dirty: %8lu kB\n"
- "Private_Clean: %8lu kB\n"
- "Private_Dirty: %8lu kB\n",
- vma_len >> 10,
- mss.resident >> 10,
- mss.shared_clean >> 10,
- mss.shared_dirty >> 10,
- mss.private_clean >> 10,
- mss.private_dirty >> 10);
- return 0;
+ return show_map_internal(m, v, &mss);
}

static void *m_start(struct seq_file *m, loff_t *pos)
@@ -288,7 +293,7 @@
/*
* We remember last_addr rather than next_addr to hit with
* mmap_cache most of the time. We have zero last_addr at
- * the begining and also after lseek. We will have -1 last_addr
+ * the beginning and also after lseek. We will have -1 last_addr
* after the end of the vmas.
*/
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