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Date: Wed, 6 Jun 2012 10:35:07 +0300
From: Boaz Harrosh <bharrosh@...asas.com>
To: Wanpeng Li <liwp.linux@...il.com>
CC: Andrew Morton <akpm@...ux-foundation.org>,
Fengguang Wu <fengguang.wu@...el.com>,
Rob Landley <rob@...dley.net>,
Alexander Viro <viro@...iv.linux.org.uk>,
"Eric W.Biederman" <ebiederm@...ssion.com>,
Lucas De Marchi <lucas.demarchi@...fusion.mobi>,
"David S. Miller" <davem@...emloft.net>, Jan Kara <jack@...e.cz>,
Mel Gorman <mgorman@...e.de>,
Minchan Kim <minchan.kim@...il.com>,
James Morris <james.l.morris@...cle.com>,
Ingo Molnar <mingo@...e.hu>,
Michel Lespinasse <walken@...gle.com>,
<linux-doc@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
<linux-fsdevel@...r.kernel.org>,
Gavin Shan <shangw@...ux.vnet.ibm.com>,
Wanpeng Li <liwp@...ux.vnet.ibm.com>
Subject: Re: [PATCH v3] remove no longer use of pdflush interface
On 06/06/2012 08:26 AM, Wanpeng Li wrote:
> From: Wanpeng Li <liwp@...ux.vnet.ibm.com>
>
> 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@...ux.vnet.ibm.com>
>
> ------------------
>
> 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@...ux.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.
> 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@...il.com>, Jason Baron <jbaron@...hat.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@...ux.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,
> 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);
What Andrew meant is that if you use printk_once here than it means you will
no longer be able to also use this generic functions for other obsolete
entries. Since only the very first one will print.
Boaz
> + 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 */
--
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