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Re: [PATCH 4/4] mtd: nand: nandsim: convert to memalloc_noreclaim_*()

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On Wed 05-04-17 09:47:00, Vlastimil Babka wrote:
> Nandsim has own functions set_memalloc() and clear_memalloc() for robust
> setting and clearing of PF_MEMALLOC. Replace them by the new generic helpers.
> No functional change.

This one smells like an abuser. Why the hell should read/write path
touch memory reserves at all!

> 
> Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
> Cc: Boris Brezillon <boris.brezillon@free-electrons.com>
> Cc: Richard Weinberger <richard@nod.at>
> ---
>  drivers/mtd/nand/nandsim.c | 29 +++++++++--------------------
>  1 file changed, 9 insertions(+), 20 deletions(-)
> 
> diff --git a/drivers/mtd/nand/nandsim.c b/drivers/mtd/nand/nandsim.c
> index cef818f535ed..03a0d057bf2f 100644
> --- a/drivers/mtd/nand/nandsim.c
> +++ b/drivers/mtd/nand/nandsim.c
> @@ -40,6 +40,7 @@
>  #include <linux/list.h>
>  #include <linux/random.h>
>  #include <linux/sched.h>
> +#include <linux/sched/mm.h>
>  #include <linux/fs.h>
>  #include <linux/pagemap.h>
>  #include <linux/seq_file.h>
> @@ -1368,31 +1369,18 @@ static int get_pages(struct nandsim *ns, struct file *file, size_t count, loff_t
>  	return 0;
>  }
>  
> -static int set_memalloc(void)
> -{
> -	if (current->flags & PF_MEMALLOC)
> -		return 0;
> -	current->flags |= PF_MEMALLOC;
> -	return 1;
> -}
> -
> -static void clear_memalloc(int memalloc)
> -{
> -	if (memalloc)
> -		current->flags &= ~PF_MEMALLOC;
> -}
> -
>  static ssize_t read_file(struct nandsim *ns, struct file *file, void *buf, size_t count, loff_t pos)
>  {
>  	ssize_t tx;
> -	int err, memalloc;
> +	int err;
> +	unsigned int noreclaim_flag;
>  
>  	err = get_pages(ns, file, count, pos);
>  	if (err)
>  		return err;
> -	memalloc = set_memalloc();
> +	noreclaim_flag = memalloc_noreclaim_save();
>  	tx = kernel_read(file, pos, buf, count);
> -	clear_memalloc(memalloc);
> +	memalloc_noreclaim_restore(noreclaim_flag);
>  	put_pages(ns);
>  	return tx;
>  }
> @@ -1400,14 +1388,15 @@ static ssize_t read_file(struct nandsim *ns, struct file *file, void *buf, size_
>  static ssize_t write_file(struct nandsim *ns, struct file *file, void *buf, size_t count, loff_t pos)
>  {
>  	ssize_t tx;
> -	int err, memalloc;
> +	int err;
> +	unsigned int noreclaim_flag;
>  
>  	err = get_pages(ns, file, count, pos);
>  	if (err)
>  		return err;
> -	memalloc = set_memalloc();
> +	noreclaim_flag = memalloc_noreclaim_save();
>  	tx = kernel_write(file, buf, count, pos);
> -	clear_memalloc(memalloc);
> +	memalloc_noreclaim_restore(noreclaim_flag);
>  	put_pages(ns);
>  	return tx;
>  }
> -- 
> 2.12.2

-- 
Michal Hocko
SUSE Labs

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[PATCH 0/4] more robust PF_MEMALLOC handling Vlastimil Babka <vbabka@suse.cz> - 2017-04-05 09:50 +0200
  [PATCH 3/4] treewide: convert PF_MEMALLOC manipulations to new helpers Vlastimil Babka <vbabka@suse.cz> - 2017-04-05 09:50 +0200
    Re: [PATCH 3/4] treewide: convert PF_MEMALLOC manipulations to new  helpers Michal Hocko <mhocko@kernel.org> - 2017-04-05 13:40 +0200
      Re: [Nbd] [PATCH 3/4] treewide: convert PF_MEMALLOC manipulations to  new helpers Wouter Verhelst <w@uter.be> - 2017-04-06 09:00 +0200
        Re: [Nbd] [PATCH 3/4] treewide: convert PF_MEMALLOC manipulations to  new helpers Mel Gorman <mgorman@techsingularity.net> - 2017-04-06 13:30 +0200
  [PATCH 1/4] mm: prevent potential recursive reclaim due to clearing PF_MEMALLOC Vlastimil Babka <vbabka@suse.cz> - 2017-04-05 09:50 +0200
    Re: [PATCH 1/4] mm: prevent potential recursive reclaim due to  clearing PF_MEMALLOC Michal Hocko <mhocko@kernel.org> - 2017-04-05 13:30 +0200
    Re: [PATCH 1/4] mm: prevent potential recursive reclaim due to clearing PF_MEMALLOC "Hillf Danton" <hillf.zj@alibaba-inc.com> - 2017-04-07 09:40 +0200
    Re: [PATCH 1/4] mm: prevent potential recursive reclaim due to  clearing PF_MEMALLOC Vlastimil Babka <vbabka@suse.cz> - 2017-04-07 11:30 +0200
  [PATCH 4/4] mtd: nand: nandsim: convert to memalloc_noreclaim_*() Vlastimil Babka <vbabka@suse.cz> - 2017-04-05 09:50 +0200
    Re: [PATCH 4/4] mtd: nand: nandsim: convert to memalloc_noreclaim_*() Vlastimil Babka <vbabka@suse.cz> - 2017-04-05 13:40 +0200
      Re: [PATCH 4/4] mtd: nand: nandsim: convert to memalloc_noreclaim_*() Michal Hocko <mhocko@kernel.org> - 2017-04-05 14:20 +0200
      Re: [PATCH 4/4] mtd: nand: nandsim: convert to memalloc_noreclaim_*() Adrian Hunter <adrian.hunter@intel.com> - 2017-04-06 08:50 +0200
        Re: [PATCH 4/4] mtd: nand: nandsim: convert to memalloc_noreclaim_*() Michal Hocko <mhocko@kernel.org> - 2017-04-06 09:30 +0200
    Re: [PATCH 4/4] mtd: nand: nandsim: convert to memalloc_noreclaim_*() Michal Hocko <mhocko@kernel.org> - 2017-04-05 13:40 +0200
      Re: [PATCH 4/4] mtd: nand: nandsim: convert to memalloc_noreclaim_*() Richard Weinberger <richard@nod.at> - 2017-04-05 13:40 +0200

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