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

From: Eric W. Biederman
Date: Tue Jun 05 2012 - 13:43:36 EST

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In reply to: Wanpeng Li: "[PATCH] remove no longer use of pdflush interface"
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Wanpeng Li <liwp.linux@xxxxxxxxx> writes:

> From: Wanpeng Li <liwp@xxxxxxxxxxxxxxxxxx>
>
> ------------------
>
> Change in v2:
>
> * add printk warning
> * add description in Documentation

Do we have old distributions or other users commonly using
nr_pdflush_threads?

Otherwise we should just remove the tunable as it is a big complicated
no-op.

If someone is using it we need to do the entire rate limited warning
thing. You should at least use printk_ratelimit to keep someone from
dosing the system by writing to the file too fast.

Eric

> ------------------
>
> 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 */
--
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Next message: Luck, Tony: "RE: [PATCH 0/6] x86/cpu hotplug: Wake up offline CPU via mwait ornmi"
Previous message: Andrea Arcangeli: "Re: [PATCH 04/35] autonuma: define _PAGE_NUMA_PTE and _PAGE_NUMA_PMD"
In reply to: Wanpeng Li: "[PATCH] remove no longer use of pdflush interface"
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