RE: [f2fs-dev] [PATCH 2/3] f2fs crypto: use bounce pages from mempool first

[Chao Yu <chao2.yu@samsung.com>]

Hi Jaegeuk,

> -----Original Message-----
> From: Jaegeuk Kim [mailto:jaegeuk@kernel.org]
> Sent: Friday, May 22, 2015 8:40 AM
> To: linux-kernel@vger.kernel.org; linux-fsdevel@vger.kernel.org;
> linux-f2fs-devel@lists.sourceforge.net
> Cc: Jaegeuk Kim
> Subject: [f2fs-dev] [PATCH 2/3] f2fs crypto: use bounce pages from mempool first
> 
> If a lot of write streams are triggered, alloc_page and __free_page are
> costly called, resulting in high memory pressure.
> 
> In order to avoid that, let's reuse mempool pages for writeback pages.
> 
> Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
> ---
>  fs/f2fs/crypto.c | 16 ++++------------
>  1 file changed, 4 insertions(+), 12 deletions(-)
> 
> diff --git a/fs/f2fs/crypto.c b/fs/f2fs/crypto.c
> index 2c7819a..2ceee68 100644
> --- a/fs/f2fs/crypto.c
> +++ b/fs/f2fs/crypto.c
> @@ -408,20 +408,12 @@ struct page *f2fs_encrypt(struct inode *inode,
>  		return (struct page *)ctx;
> 
>  	/* The encryption operation will require a bounce page. */
> -	ciphertext_page = alloc_page(GFP_NOFS);
> +	ciphertext_page = mempool_alloc(f2fs_bounce_page_pool, GFP_NOFS);
>  	if (!ciphertext_page) {
> -		/*
> -		 * This is a potential bottleneck, but at least we'll have
> -		 * forward progress.
> -		 */
> -		ciphertext_page = mempool_alloc(f2fs_bounce_page_pool,
> -							GFP_NOFS);
> -		if (WARN_ON_ONCE(!ciphertext_page))
> -			ciphertext_page = mempool_alloc(f2fs_bounce_page_pool,
> -						GFP_NOFS | __GFP_WAIT);
> -		ctx->flags &= ~F2FS_BOUNCE_PAGE_REQUIRES_FREE_ENCRYPT_FL;
> -	} else {
> +		ciphertext_page = alloc_page(GFP_NOFS);

Using alloc_page(GFP_NOFS | __GFP_WAIT) to avoid failure?

Thanks,

>  		ctx->flags |= F2FS_BOUNCE_PAGE_REQUIRES_FREE_ENCRYPT_FL;
> +	} else {
> +		ctx->flags &= ~F2FS_BOUNCE_PAGE_REQUIRES_FREE_ENCRYPT_FL;
>  	}
>  	ctx->flags |= F2FS_WRITE_PATH_FL;
>  	ctx->w.bounce_page = ciphertext_page;
> --
> 2.1.1
> 
> 
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