Re: [Nbd] [PATCH 4/4] mtd: nand: nandsim: convert to memalloc_noreclaim_*()
- To: Vlastimil Babka <vbabka@...1290...>
- Cc: nbd-general@lists.sourceforge.net, Boris Brezillon <boris.brezillon@...1551...>, Richard Weinberger <richard@...2889...>, linux-scsi@...25..., netdev@...25..., linux-kernel@...25..., linux-block@...25..., linux-mm@...1312..., Johannes Weiner <hannes@...1554...>, Andrew Morton <akpm@...133...>, open-iscsi@...2887..., Mel Gorman <mgorman@...2888...>
- Subject: Re: [Nbd] [PATCH 4/4] mtd: nand: nandsim: convert to memalloc_noreclaim_*()
- From: Michal Hocko <mhocko@...1285...>
- Date: Wed, 5 Apr 2017 13:31:57 +0200
- Message-id: <20170405113157.GM6035@...2894...>
- In-reply-to: <20170405074700.29871-5-vbabka@...1290...>
- References: <20170405074700.29871-1-vbabka@...1290...> <20170405074700.29871-5-vbabka@...1290...>
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@...1290...>
> Cc: Boris Brezillon <boris.brezillon@...1551...>
> Cc: Richard Weinberger <richard@...2889...>
> ---
> 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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