Commit 3965c9ae authored by Wanpeng Li's avatar Wanpeng Li Committed by Linus Torvalds

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: default avatarWanpeng Li <liwp@linux.vnet.ibm.com>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent deaf386e
What: /proc/sys/vm/nr_pdflush_threads
Date: June 2012
Contact: Wanpeng Li <liwp@linux.vnet.ibm.com>
Description: Since pdflush is replaced by per-BDI flusher, the interface of old pdflush
exported in /proc/sys/vm/ should be removed.
......@@ -13,6 +13,14 @@ Who: Jim Cromie <jim.cromie@gmail.com>, Jason Baron <jbaron@redhat.com>
---------------------------
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@linux.vnet.ibm.com>
---------------------------
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,
......
......@@ -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.
......
......@@ -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.
......
......@@ -17,6 +17,7 @@
#include <linux/timer.h>
#include <linux/writeback.h>
#include <linux/atomic.h>
#include <linux/sysctl.h>
struct page;
struct device;
......@@ -304,6 +305,8 @@ void clear_bdi_congested(struct backing_dev_info *bdi, int sync);
void set_bdi_congested(struct backing_dev_info *bdi, int sync);
long congestion_wait(int sync, long timeout);
long wait_iff_congested(struct zone *zone, int sync, long timeout);
int pdflush_proc_obsolete(struct ctl_table *table, int write,
void __user *buffer, size_t *lenp, loff_t *ppos);
static inline bool bdi_cap_writeback_dirty(struct backing_dev_info *bdi)
{
......
......@@ -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 */
......@@ -1102,10 +1102,8 @@ static struct ctl_table vm_table[] = {
},
{
.procname = "nr_pdflush_threads",
.data = &nr_pdflush_threads,
.maxlen = sizeof nr_pdflush_threads,
.mode = 0444 /* read-only*/,
.proc_handler = proc_dointvec,
.mode = 0444 /* read-only */,
.proc_handler = pdflush_proc_obsolete,
},
{
.procname = "swappiness",
......
......@@ -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 */
......
......@@ -886,3 +886,23 @@ long wait_iff_congested(struct zone *zone, int sync, long timeout)
return ret;
}
EXPORT_SYMBOL(wait_iff_congested);
int pdflush_proc_obsolete(struct ctl_table *table, int write,
void __user *buffer, size_t *lenp, loff_t *ppos)
{
char kbuf[] = "0\n";
if (*ppos) {
*lenp = 0;
return 0;
}
if (copy_to_user(buffer, kbuf, sizeof(kbuf)))
return -EFAULT;
printk_once(KERN_WARNING "%s exported in /proc is scheduled for removal\n",
table->procname);
*lenp = 2;
*ppos += *lenp;
return 2;
}
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