linux-ext4 - Re: [RFC PATCH v3 7/8] ext4: remove bdev_try_to_free

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Message-ID: <20210607155023.GC29326@quack2.suse.cz>
Date:   Mon, 7 Jun 2021 17:50:23 +0200
From:   Jan Kara <jack@...e.cz>
To:     Zhang Yi <yi.zhang@...wei.com>
Cc:     linux-ext4@...r.kernel.org, tytso@....edu,
        adilger.kernel@...ger.ca, jack@...e.cz, yukuai3@...wei.com
Subject: Re: [RFC PATCH v3 7/8] ext4: remove bdev_try_to_free_page() callback

On Thu 27-05-21 21:56:40, Zhang Yi wrote:
> After we introduce a jbd2 shrinker to release checkpointed buffer's
> journal head, we could free buffer without bdev_try_to_free_page()
> under memory pressure. So this patch remove the whole
> bdev_try_to_free_page() callback directly. It also remove many
> use-after-free issues relate to it together.
> 
> Signed-off-by: Zhang Yi <yi.zhang@...wei.com>

Looks good. Feel free to add:

Reviewed-by: Jan Kara <jack@...e.cz>

								Honza

> ---
>  fs/ext4/super.c | 21 ---------------------
>  1 file changed, 21 deletions(-)
> 
> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> index bf6d0085e1b7..b778236d06e6 100644
> --- a/fs/ext4/super.c
> +++ b/fs/ext4/super.c
> @@ -1442,26 +1442,6 @@ static int ext4_nfs_commit_metadata(struct inode *inode)
>  	return ext4_write_inode(inode, &wbc);
>  }
>  
> -/*
> - * Try to release metadata pages (indirect blocks, directories) which are
> - * mapped via the block device.  Since these pages could have journal heads
> - * which would prevent try_to_free_buffers() from freeing them, we must use
> - * jbd2 layer's try_to_free_buffers() function to release them.
> - */
> -static int bdev_try_to_free_page(struct super_block *sb, struct page *page,
> -				 gfp_t wait)
> -{
> -	journal_t *journal = EXT4_SB(sb)->s_journal;
> -
> -	WARN_ON(PageChecked(page));
> -	if (!page_has_buffers(page))
> -		return 0;
> -	if (journal)
> -		return jbd2_journal_try_to_free_buffers(journal, page);
> -
> -	return try_to_free_buffers(page);
> -}
> -
>  #ifdef CONFIG_FS_ENCRYPTION
>  static int ext4_get_context(struct inode *inode, void *ctx, size_t len)
>  {
> @@ -1656,7 +1636,6 @@ static const struct super_operations ext4_sops = {
>  	.quota_write	= ext4_quota_write,
>  	.get_dquots	= ext4_get_dquots,
>  #endif
> -	.bdev_try_to_free_page = bdev_try_to_free_page,
>  };
>  
>  static const struct export_operations ext4_export_ops = {
> -- 
> 2.25.4
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR