mm: prepare for removal of obsolete /proc/sys/vm/nr_pdflush_threads

Since per-BDI flusher threads were introduced in 2.6, the pdflush
mechanism is not used any more.  But the old interface exported through
/proc/sys/vm/nr_pdflush_threads still exists and is obviously useless.

For back-compatibility, printk warning information and return 2 to notify
the users that the interface is removed.

Signed-off-by: Wanpeng Li <liwp@linux.vnet.ibm.com>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 3 insertions, 5 deletions

diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 97186b99b0e4..6502d35a25ba 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -1101,11 +1101,9 @@ static struct ctl_table vm_table[] = {
                 .extra1         = &zero,
         },
         {
-                .procname       = "nr_pdflush_threads",
-                .data           = &nr_pdflush_threads,
-                .maxlen         = sizeof nr_pdflush_threads,
-                .mode           = 0444 /* read-only*/,
-                .proc_handler   = proc_dointvec,
+                .procname       = "nr_pdflush_threads",
+                .mode           = 0444 /* read-only */,
+                .proc_handler   = pdflush_proc_obsolete,
         },
         {
                 .procname       = "swappiness",