[PATCH v3] remove no longer use of pdflush interface

From: Wanpeng Li
Date: Wed Jun 06 2012 - 01:27:17 EST

From: Wanpeng Li <liwp@xxxxxxxxxxxxxxxxxx>

Since per-BDI flusher introduced to linux 2.6, pdflush mechanism is not
used any more. But the old interface of pdflush exported in /proc/sys/vm/
is still there. In order to take attention to back-compatibility issues,
printk warning information and return -ENOSYS to notice the users the
interface is removed.

Signed-off-by: Wanpeng Li <liwp@xxxxxxxxxxxxxxxxxx>

------------------

v3:

* rename proc_deprecated() to proc_obsolete()
* replace printk in proc_obsolete by prink_once and change warning information

v2:

* add printk warning
* add description in Documentation

v1:

* remove nr_pdflush_threads associated codes

------------------
---
.../ABI/obsolete/proc-sys-vm-nr_pdflush_threads | 5 +++++
Documentation/feature-removal-schedule.txt | 8 ++++++++
Documentation/sysctl/vm.txt | 11 -----------
fs/fs-writeback.c | 5 -----
include/linux/sysctl.h | 3 +++
include/linux/writeback.h | 5 -----
kernel/sysctl.c | 18 +++++++++++++-----
kernel/sysctl_binary.c | 2 +-
8 files changed, 30 insertions(+), 27 deletions(-)
create mode 100644 Documentation/ABI/obsolete/proc-sys-vm-nr_pdflush_threads

diff --git a/Documentation/ABI/obsolete/proc-sys-vm-nr_pdflush_threads b/Documentation/ABI/obsolete/proc-sys-vm-nr_pdflush_threads
new file mode 100644
index 0000000..edbe548
--- /dev/null
+++ b/Documentation/ABI/obsolete/proc-sys-vm-nr_pdflush_threads
@@ -0,0 +1,5 @@
+What: /proc/sys/vm/nr_pdflush_threads
+Date: June 2012
+Contact: Wanpeng Li <liwp@xxxxxxxxxxxxxxxxxx>
+Description: Since pdflush is replaced by per-BDI flusher, the interface of old pdflush
+ exported in /proc/sys/vm/ should be removed.
diff --git a/Documentation/feature-removal-schedule.txt b/Documentation/feature-removal-schedule.txt
index 56000b3..8e4a60c 100644
--- a/Documentation/feature-removal-schedule.txt
+++ b/Documentation/feature-removal-schedule.txt
@@ -13,6 +13,14 @@ Who: Jim Cromie <jim.cromie@xxxxxxxxx>, Jason Baron <jbaron@xxxxxxxxxx>

---------------------------

+What: /proc/sys/vm/nr_pdflush_threads
+When: 2012
+Why: Since pdflush is deprecated, the interface exported in /proc/sys/vm/
+ should be removed.
+Who: Wanpeng Li <liwp@xxxxxxxxxxxxxxxxxx>
+
+---------------------------
+
What: CONFIG_APM_CPU_IDLE, and its ability to call APM BIOS in idle
When: 2012
Why: This optional sub-feature of APM is of dubious reliability,
diff --git a/Documentation/sysctl/vm.txt b/Documentation/sysctl/vm.txt
index 96f0ee8..71c17d2 100644
--- a/Documentation/sysctl/vm.txt
+++ b/Documentation/sysctl/vm.txt
@@ -42,7 +42,6 @@ Currently, these files are in /proc/sys/vm:
- mmap_min_addr
- nr_hugepages
- nr_overcommit_hugepages
-- nr_pdflush_threads
- nr_trim_pages (only if CONFIG_MMU=n)
- numa_zonelist_order
- oom_dump_tasks
@@ -426,16 +425,6 @@ See Documentation/vm/hugetlbpage.txt

==============================================================

-nr_pdflush_threads
-
-The current number of pdflush threads. This value is read-only.
-The value changes according to the number of dirty pages in the system.
-
-When necessary, additional pdflush threads are created, one per second, up to
-nr_pdflush_threads_max.
-
-==============================================================
-
nr_trim_pages

This is available only on NOMMU kernels.
diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 8d2fb8c..f2d0109 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -52,11 +52,6 @@ struct wb_writeback_work {
struct completion *done; /* set if the caller waits */
};

-/*
- * We don't actually have pdflush, but this one is exported though /proc...
- */
-int nr_pdflush_threads;
-
/**
* writeback_in_progress - determine whether there is writeback in progress
* @bdi: the device's backing_dev_info structure.
diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h
index c34b4c8..5fa7bfa 100644
--- a/include/linux/sysctl.h
+++ b/include/linux/sysctl.h
@@ -964,6 +964,9 @@ extern int proc_doulongvec_ms_jiffies_minmax(struct ctl_table *table, int,
void __user *, size_t *, loff_t *);
extern int proc_do_large_bitmap(struct ctl_table *, int,
void __user *, size_t *, loff_t *);
+extern int proc_obsolete(struct ctl_table *, int,
+ void __user *, size_t *, loff_t *);
+

/*
* Register a set of sysctl names by calling register_sysctl_table
diff --git a/include/linux/writeback.h b/include/linux/writeback.h
index 6d0a0fc..c66fe33 100644
--- a/include/linux/writeback.h
+++ b/include/linux/writeback.h
@@ -189,9 +189,4 @@ void tag_pages_for_writeback(struct address_space *mapping,

void account_page_redirty(struct page *page);

-/* pdflush.c */
-extern int nr_pdflush_threads; /* Global so it can be exported to sysctl
- read-only. */
-
-
#endif /* WRITEBACK_H */
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 4ab1187..8d95a54 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -1095,11 +1095,9 @@ 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 = proc_obsolete,
},
{
.procname = "swappiness",
@@ -2505,6 +2503,15 @@ int proc_doulongvec_ms_jiffies_minmax(struct ctl_table *table, int write,

#endif /* CONFIG_PROC_SYSCTL */

+/* notice associated proc obsoleted */
+int proc_obsolete(struct ctl_table *table, int write,
+ void __user *buffer, size_t *lenp, loff_t *ppos)
+{
+ printk_once(KERN_WARNING "%s exported in /proc is scheduled for removal\n",
+ table->procname);
+ return -ENOSYS;
+}
+
/*
* No sense putting this after each symbol definition, twice,
* exception granted :-)
@@ -2517,3 +2524,4 @@ EXPORT_SYMBOL(proc_dointvec_ms_jiffies);
EXPORT_SYMBOL(proc_dostring);
EXPORT_SYMBOL(proc_doulongvec_minmax);
EXPORT_SYMBOL(proc_doulongvec_ms_jiffies_minmax);
+EXPORT_SYMBOL(proc_obsolete);
diff --git a/kernel/sysctl_binary.c b/kernel/sysctl_binary.c
index a650694..65bdcf1 100644
--- a/kernel/sysctl_binary.c
+++ b/kernel/sysctl_binary.c
@@ -147,7 +147,7 @@ static const struct bin_table bin_vm_table[] = {
{ CTL_INT, VM_DIRTY_RATIO, "dirty_ratio" },
/* VM_DIRTY_WB_CS "dirty_writeback_centisecs" no longer used */
/* VM_DIRTY_EXPIRE_CS "dirty_expire_centisecs" no longer used */
- { CTL_INT, VM_NR_PDFLUSH_THREADS, "nr_pdflush_threads" },
+ /* VM_NR_PDFLUSH_THREADS "nr_pdflush_threads" no longer used */
{ CTL_INT, VM_OVERCOMMIT_RATIO, "overcommit_ratio" },
/* VM_PAGEBUF unused */
/* VM_HUGETLB_PAGES "nr_hugepages" no longer used */
--
1.7.9.5

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