linux-kernel - Re: [f2fs-dev] [PATCH v2] f2fs: don't use GFP

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Message-ID: <20180410013545.GA45603@jaegeuk-macbookpro.roam.corp.google.com>
Date:   Mon, 9 Apr 2018 18:35:45 -0700
From:   Jaegeuk Kim <jaegeuk@...nel.org>
To:     linux-kernel@...r.kernel.org,
        linux-f2fs-devel@...ts.sourceforge.net
Subject: Re: [f2fs-dev] [PATCH v2] f2fs: don't use GFP_ZERO for page caches

On 04/09, Jaegeuk Kim wrote:
> Change log from v1:
>  - don't memset for recovered page
> 
> Related to https://lkml.org/lkml/2018/4/8/661
> 
> Sometimes, we need to write meta data to new allocated block address,
> then we will allocate a zeroed page in inner inode's address space, and
> fill partial data in it, and leave other place with zero value which means
> some fields are initial status.
> 
> There are two inner inodes (meta inode and node inode) setting __GFP_ZERO,
> I have just checked them, for both of them, we can avoid using __GFP_ZERO,
> and do initialization by ourselves to avoid unneeded/redundant zeroing
> from mm.

Okay, it seems we're missing some more places to reset the memory, since
I'm still getting a panic. :(

Thanks,

> 
> Cc: <stable@...r.kernel.org>
> Signed-off-by: Chao Yu <yuchao0@...wei.com>
> Signed-off-by: Jaegeuk Kim <jaegeuk@...nel.org>
> ---
>  fs/f2fs/inode.c | 4 ++--
>  fs/f2fs/node.c  | 3 ++-
>  2 files changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/f2fs/inode.c b/fs/f2fs/inode.c
> index 417c9dcd0269..87535bf63421 100644
> --- a/fs/f2fs/inode.c
> +++ b/fs/f2fs/inode.c
> @@ -320,10 +320,10 @@ struct inode *f2fs_iget(struct super_block *sb, unsigned long ino)
>  make_now:
>  	if (ino == F2FS_NODE_INO(sbi)) {
>  		inode->i_mapping->a_ops = &f2fs_node_aops;
> -		mapping_set_gfp_mask(inode->i_mapping, GFP_F2FS_ZERO);
> +		mapping_set_gfp_mask(inode->i_mapping, GFP_NOFS);
>  	} else if (ino == F2FS_META_INO(sbi)) {
>  		inode->i_mapping->a_ops = &f2fs_meta_aops;
> -		mapping_set_gfp_mask(inode->i_mapping, GFP_F2FS_ZERO);
> +		mapping_set_gfp_mask(inode->i_mapping, GFP_NOFS);
>  	} else if (S_ISREG(inode->i_mode)) {
>  		inode->i_op = &f2fs_file_inode_operations;
>  		inode->i_fop = &f2fs_file_operations;
> diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
> index 9a99243054ba..5a4469093e43 100644
> --- a/fs/f2fs/node.c
> +++ b/fs/f2fs/node.c
> @@ -1096,7 +1096,8 @@ struct page *new_node_page(struct dnode_of_data *dn, unsigned int ofs)
>  	set_node_addr(sbi, &new_ni, NEW_ADDR, false);
>  
>  	f2fs_wait_on_page_writeback(page, NODE, true);
> -	fill_node_footer(page, dn->nid, dn->inode->i_ino, ofs, true);
> +	memset(F2FS_NODE(page), 0, PAGE_SIZE);
> +	fill_node_footer(page, dn->nid, dn->inode->i_ino, ofs, false);
>  	set_cold_node(page, S_ISDIR(dn->inode->i_mode));
>  	if (!PageUptodate(page))
>  		SetPageUptodate(page);
> -- 
> 2.15.0.531.g2ccb3012c9-goog
> 
> 
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