Re: [PATCH v2] remove no longer use of pdflush interface

[Wanpeng Li]

On Tue, Jun 05, 2012 at 10:45:20PM +0800, Gavin Shan wrote:

Hi Gavin,

>
>- Why not just remove the proc entry since we needn't it anymore?

Some user applications maybe still use this interface, so we should take
attention to back-compatibility issues.

>- If we really want to keep the entry and just output warning message, we *only*
>  can see the message out of system console. It's reasonable to put the message
>  into the buffer directly so that any users from system console/telnet/ssh can
>  see the warning message?

Maybe this is a good idea.

>
>>From: Wanpeng Li <liwp@xxxxxxxxxxxxxxxxxx>
>>
>>------------------
>>
>>Change in v2:
>>
>>* add printk warning
>>* add description in Documentation
>>
>>------------------
>>
>>Signed-off-by: Wanpeng Li <liwp@xxxxxxxxxxxxxxxxxx>
>>---
>> .../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 e4b5775..7eea1ee 100644
>>--- a/Documentation/feature-removal-schedule.txt
>>+++ b/Documentation/feature-removal-schedule.txt
>>@@ -6,6 +6,14 @@ be removed from this file.
>>
>> ---------------------------
>>
>>+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 539f36c..30ddb8a 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..f25be74 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_deprecated(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 a2b84f5..13b5df7 100644
>>--- a/include/linux/writeback.h
>>+++ b/include/linux/writeback.h
>>@@ -193,9 +193,4 @@ 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..1ab53cb 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_deprecated,
>> 	},
>> 	{
>> 		.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 deprecated */
>>+int proc_deprecated(struct ctl_table *table, int write,
>>+		    void __user *buffer, size_t *lenp, loff_t *ppos)
>>+{
>>+	printk(KERN_WARNING "%s exported in /proc is deprecated\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_deprecated);
>>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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