linux-ext4 - Re: [PATCH V2] fs/ext2: Use ext2_put

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Date:   Fri, 13 Nov 2020 11:23:51 +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 V2] fs/ext2: Use ext2_put_page

On Thu 12-11-20 09:42:44, 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_put_page() to ext2.h and use it 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>
> 
> ---
> Changes from V1:
> 	Reported-by: kernel test robot <lkp@...el.com>
> 	move ext2_get_page() back to dir.c; my testing must have had the
> 	wrong .config because I did not see the compile error
> 	yesterday...

Drat, and I forgot a compilation test as well :-| My bad. Thanks for the
fix anyway!
	
								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   | 14 ++++++++------
>  fs/ext2/ext2.h  |  7 +++++++
>  fs/ext2/namei.c | 15 +++++----------
>  3 files changed, 20 insertions(+), 16 deletions(-)
> 
> diff --git a/fs/ext2/dir.c b/fs/ext2/dir.c
> index 70355ab6740e..14aa45316ad2 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.
> @@ -336,6 +330,8 @@ 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 +397,12 @@ 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..2a4175fbaf5e 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 +747,11 @@ 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);
> +}
>  
>  /* 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