mpol_to_str() may fail, and not fill the buffer (e.g. -EINVAL), so need
check about it, or buffer may not be zero based, and next seq_printf()
will cause issue.

Also print related warning when the buffer space is not enough.


Signed-off-by: Chen Gang <gang.c...@asianux.com>
---
 mm/shmem.c |   15 ++++++++++++++-
 1 files changed, 14 insertions(+), 1 deletions(-)

diff --git a/mm/shmem.c b/mm/shmem.c
index 75010ba..eb4eec8 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -886,11 +886,24 @@ redirty:
 static void shmem_show_mpol(struct seq_file *seq, struct mempolicy *mpol)
 {
        char buffer[64];
+       int ret;
 
        if (!mpol || mpol->mode == MPOL_DEFAULT)
                return;         /* show nothing */
 
-       mpol_to_str(buffer, sizeof(buffer), mpol);
+       ret = mpol_to_str(buffer, sizeof(buffer), mpol);
+       if (ret < 0)
+               switch (ret) {
+               case -ENOSPC:
+                       printk(KERN_WARNING
+                               "in %s: string is truncated in 
mpol_to_str().\n",
+                               __func__);
+               default:
+                       printk(KERN_ERR
+                               "in %s: call mpol_to_str() fail, errcode: %d. 
buffer: %p, size: %zu, pol: %p\n",
+                               __func__, ret, buffer, sizeof(buffer), mpol);
+                       return;
+               }
 
        seq_printf(seq, ",mpol=%s", buffer);
 }
-- 
1.7.7.6
--
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