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Date:   Thu, 12 Nov 2020 10:34:54 +0100
From:   Jan Kara <jack@...e.cz>
To:     ira.weiny@...el.com
Cc:     Jan Kara <jack@...e.com>, linux-ext4@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] fs/ext2: Use ext2_put_page

On Wed 11-11-20 12:55:30, ira.weiny@...el.com wrote:
> From: Ira Weiny <ira.weiny@...el.com>
> 
> There are 3 places in namei.c where the equivalent of ext2_put_page() is
> open coded on a page which was returned from the ext2_get_page() call
> [through the use of ext2_find_entry() and ext2_dotdot()].
> 
> Move ext2_get_page() and ext2_put_page() to ext2.h in order to help
> clarify the use of the get/put and then use ext2_put_page() in namei.c
> 
> Also add a comment regarding the proper way to release the page returned
> from ext2_find_entry() and ext2_dotdot().
> 
> Signed-off-by: Ira Weiny <ira.weiny@...el.com>

Thanks. Good cleanup. I've added it to my tree.

								Honza

> 
> ---
> 
> This was originally part of the kmap_thread() series here:
> 
> https://lore.kernel.org/lkml/20201009195033.3208459-37-ira.weiny@intel.com/
> 
> But this is really a valid clean up regardless of the
> kmap_thread[local]() changes.
> ---
>  fs/ext2/dir.c   | 33 ++++++++-------------------------
>  fs/ext2/ext2.h  | 27 +++++++++++++++++++++++++++
>  fs/ext2/namei.c | 15 +++++----------
>  3 files changed, 40 insertions(+), 35 deletions(-)
> 
> diff --git a/fs/ext2/dir.c b/fs/ext2/dir.c
> index 70355ab6740e..8acd77a66ff4 100644
> --- a/fs/ext2/dir.c
> +++ b/fs/ext2/dir.c
> @@ -66,12 +66,6 @@ static inline unsigned ext2_chunk_size(struct inode *inode)
>  	return inode->i_sb->s_blocksize;
>  }
>  
> -static inline void ext2_put_page(struct page *page)
> -{
> -	kunmap(page);
> -	put_page(page);
> -}
> -
>  /*
>   * Return the offset into page `page_nr' of the last valid
>   * byte in that page, plus one.
> @@ -196,25 +190,6 @@ static bool ext2_check_page(struct page *page, int quiet)
>  	return false;
>  }
>  
> -static struct page * ext2_get_page(struct inode *dir, unsigned long n,
> -				   int quiet)
> -{
> -	struct address_space *mapping = dir->i_mapping;
> -	struct page *page = read_mapping_page(mapping, n, NULL);
> -	if (!IS_ERR(page)) {
> -		kmap(page);
> -		if (unlikely(!PageChecked(page))) {
> -			if (PageError(page) || !ext2_check_page(page, quiet))
> -				goto fail;
> -		}
> -	}
> -	return page;
> -
> -fail:
> -	ext2_put_page(page);
> -	return ERR_PTR(-EIO);
> -}
> -
>  /*
>   * NOTE! unlike strncmp, ext2_match returns 1 for success, 0 for failure.
>   *
> @@ -336,6 +311,8 @@ ext2_readdir(struct file *file, struct dir_context *ctx)
>   * returns the page in which the entry was found (as a parameter - res_page),
>   * and the entry itself. Page is returned mapped and unlocked.
>   * Entry is guaranteed to be valid.
> + *
> + * On Success ext2_put_page() should be called on *res_page.
>   */
>  struct ext2_dir_entry_2 *ext2_find_entry (struct inode *dir,
>  			const struct qstr *child, struct page **res_page)
> @@ -401,6 +378,12 @@ struct ext2_dir_entry_2 *ext2_find_entry (struct inode *dir,
>  	return de;
>  }
>  
> +/**
> + * Return the '..' directory entry and the page in which the entry was found
> + * (as a parameter - p).
> + *
> + * On Success ext2_put_page() should be called on *p.
> + */
>  struct ext2_dir_entry_2 * ext2_dotdot (struct inode *dir, struct page **p)
>  {
>  	struct page *page = ext2_get_page(dir, 0, 0);
> diff --git a/fs/ext2/ext2.h b/fs/ext2/ext2.h
> index 5136b7289e8d..b4403f96858b 100644
> --- a/fs/ext2/ext2.h
> +++ b/fs/ext2/ext2.h
> @@ -16,6 +16,8 @@
>  #include <linux/blockgroup_lock.h>
>  #include <linux/percpu_counter.h>
>  #include <linux/rbtree.h>
> +#include <linux/mm.h>
> +#include <linux/highmem.h>
>  
>  /* XXX Here for now... not interested in restructing headers JUST now */
>  
> @@ -745,6 +747,31 @@ extern int ext2_delete_entry (struct ext2_dir_entry_2 *, struct page *);
>  extern int ext2_empty_dir (struct inode *);
>  extern struct ext2_dir_entry_2 * ext2_dotdot (struct inode *, struct page **);
>  extern void ext2_set_link(struct inode *, struct ext2_dir_entry_2 *, struct page *, struct inode *, int);
> +static inline void ext2_put_page(struct page *page)
> +{
> +	kunmap(page);
> +	put_page(page);
> +}
> +
> +static inline struct page * ext2_get_page(struct inode *dir, unsigned long n,
> +				   int quiet)
> +{
> +	struct address_space *mapping = dir->i_mapping;
> +	struct page *page = read_mapping_page(mapping, n, NULL);
> +	if (!IS_ERR(page)) {
> +		kmap(page);
> +		if (unlikely(!PageChecked(page))) {
> +			if (PageError(page) || !ext2_check_page(page, quiet))
> +				goto fail;
> +		}
> +	}
> +	return page;
> +
> +fail:
> +	ext2_put_page(page);
> +	return ERR_PTR(-EIO);
> +}
> +
>  
>  /* ialloc.c */
>  extern struct inode * ext2_new_inode (struct inode *, umode_t, const struct qstr *);
> diff --git a/fs/ext2/namei.c b/fs/ext2/namei.c
> index 5bf2c145643b..ea980f1e2e99 100644
> --- a/fs/ext2/namei.c
> +++ b/fs/ext2/namei.c
> @@ -389,23 +389,18 @@ static int ext2_rename (struct inode * old_dir, struct dentry * old_dentry,
>  	if (dir_de) {
>  		if (old_dir != new_dir)
>  			ext2_set_link(old_inode, dir_de, dir_page, new_dir, 0);
> -		else {
> -			kunmap(dir_page);
> -			put_page(dir_page);
> -		}
> +		else
> +			ext2_put_page(dir_page);
>  		inode_dec_link_count(old_dir);
>  	}
>  	return 0;
>  
>  
>  out_dir:
> -	if (dir_de) {
> -		kunmap(dir_page);
> -		put_page(dir_page);
> -	}
> +	if (dir_de)
> +		ext2_put_page(dir_page);
>  out_old:
> -	kunmap(old_page);
> -	put_page(old_page);
> +	ext2_put_page(old_page);
>  out:
>  	return err;
>  }
> -- 
> 2.28.0.rc0.12.gb6a658bd00c9
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR

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