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Date:   Sun, 15 May 2022 16:53:49 -0700
From:   Ira Weiny <ira.weiny@intel.com>
To:     "Fabio M. De Francesco" <fmdefrancesco@gmail.com>
Cc:     Evgeniy Dushistov <dushistov@mail.ru>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] fs/ufs: Replace kmap() with kmap_local_page()
Message-ID: <YoGSjZlucCKjSxVX@iweiny-desk3>
References: <20220509071207.16176-1-fmdefrancesco@gmail.com>
MIME-Version: 1.0
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Content-Disposition: inline
In-Reply-To: <20220509071207.16176-1-fmdefrancesco@gmail.com>
Precedence: bulk

On Mon, May 09, 2022 at 09:12:07AM +0200, Fabio M. De Francesco wrote:
> The use of kmap() is being deprecated in favor of kmap_local_page(). With
> kmap_local_page(), the mapping is thread-local, CPU-local and not globally
> visible.
> 
> The usage of kmap_local_page() in fs/ufs is thread-local, therefore replace
> kmap() / kunmap() calls with kmap_local_page() / kunmap_local().
> 
> kunmap_local() requires the mapping address, so return that address from
> ufs_get_page() to be used in ufs_put_page().
> 
> These changes are essentially ported from fs/ext2 and relie largely on
> commit 782b76d7abdf ("fs/ext2: Replace kmap() with kmap_local_page()").
> 
> Suggested-by: Ira Weiny <ira.weiny@intel.com>
> Signed-off-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>
> ---
> 
> v1 -> v2: Correct some style's issues reported by checkpatch.pl.
> 	  Remove "inline" compiler directive from fs/ufs/ufs.h,
> 	  Reported-by: kernel test robot <lkp@intel.com>
> 
>  fs/ufs/dir.c   | 116 +++++++++++++++++++++++++++++++------------------
>  fs/ufs/namei.c |  38 ++++++++--------
>  fs/ufs/ufs.h   |  12 +++--
>  3 files changed, 102 insertions(+), 64 deletions(-)
> 
> diff --git a/fs/ufs/dir.c b/fs/ufs/dir.c
> index b721d0bda5e5..39e81547ebb9 100644
> --- a/fs/ufs/dir.c
> +++ b/fs/ufs/dir.c
> @@ -61,9 +61,9 @@ static int ufs_commit_chunk(struct page *page, loff_t pos, unsigned len)
>  	return err;
>  }
>  
> -static inline void ufs_put_page(struct page *page)
> +inline void ufs_put_page(struct page *page, void *page_addr)
>  {
> -	kunmap(page);
> +	kunmap_local(page_addr);
>  	put_page(page);
>  }
>  
> @@ -72,11 +72,12 @@ ino_t ufs_inode_by_name(struct inode *dir, const struct qstr *qstr)
>  	ino_t res = 0;
>  	struct ufs_dir_entry *de;
>  	struct page *page;
> -	
> -	de = ufs_find_entry(dir, qstr, &page);
> +	void *page_addr;
> +
> +	de = ufs_find_entry(dir, qstr, &page, &page_addr);
>  	if (de) {
>  		res = fs32_to_cpu(dir->i_sb, de->d_ino);
> -		ufs_put_page(page);
> +		ufs_put_page(page, page_addr);
>  	}
>  	return res;
>  }
> @@ -84,11 +85,11 @@ ino_t ufs_inode_by_name(struct inode *dir, const struct qstr *qstr)
>  
>  /* Releases the page */
>  void ufs_set_link(struct inode *dir, struct ufs_dir_entry *de,
> -		  struct page *page, struct inode *inode,
> -		  bool update_times)
> +		  struct page *page, void *page_addr,
> +		  struct inode *inode, bool update_times)
>  {
>  	loff_t pos = page_offset(page) +
> -			(char *) de - (char *) page_address(page);
> +			(char *)de - (char *)page_addr;
>  	unsigned len = fs16_to_cpu(dir->i_sb, de->d_reclen);
>  	int err;
>  
> @@ -100,18 +101,17 @@ void ufs_set_link(struct inode *dir, struct ufs_dir_entry *de,
>  	ufs_set_de_type(dir->i_sb, de, inode->i_mode);
>  
>  	err = ufs_commit_chunk(page, pos, len);
> -	ufs_put_page(page);
> +	ufs_put_page(page, page_addr);
>  	if (update_times)
>  		dir->i_mtime = dir->i_ctime = current_time(dir);
>  	mark_inode_dirty(dir);
>  }
>  
>  
> -static bool ufs_check_page(struct page *page)
> +static bool ufs_check_page(struct page *page, char *kaddr)
>  {
>  	struct inode *dir = page->mapping->host;
>  	struct super_block *sb = dir->i_sb;
> -	char *kaddr = page_address(page);
>  	unsigned offs, rec_len;
>  	unsigned limit = PAGE_SIZE;
>  	const unsigned chunk_mask = UFS_SB(sb)->s_uspi->s_dirblksize - 1;
> @@ -186,21 +186,28 @@ static bool ufs_check_page(struct page *page)
>  	return false;
>  }
>  
> -static struct page *ufs_get_page(struct inode *dir, unsigned long n)
> +/*
> + * Calls to ufs_get_page()/ufs_put_page() must be nested according to the
> + * rules documented in kmap_local_page()/kunmap_local().
> + *
> + * NOTE: ufs_find_entry() and ufs_dotdot() act as calls to ufs_get_page()
> + * and must be treated accordingly for nesting purposes.
> + */
> +static struct page *ufs_get_page(struct inode *dir, unsigned long n, void **page_addr)
>  {
>  	struct address_space *mapping = dir->i_mapping;
>  	struct page *page = read_mapping_page(mapping, n, NULL);
>  	if (!IS_ERR(page)) {
> -		kmap(page);
> +		*page_addr = kmap_local_page(page);
>  		if (unlikely(!PageChecked(page))) {
> -			if (PageError(page) || !ufs_check_page(page))
> +			if (PageError(page) || !ufs_check_page(page, *page_addr))
>  				goto fail;
>  		}
>  	}
>  	return page;
>  
>  fail:
> -	ufs_put_page(page);
> +	ufs_put_page(page, *page_addr);
>  	return ERR_PTR(-EIO);
>  }
>  
> @@ -226,15 +233,29 @@ ufs_next_entry(struct super_block *sb, struct ufs_dir_entry *p)
>  					fs16_to_cpu(sb, p->d_reclen));
>  }
>  
> -struct ufs_dir_entry *ufs_dotdot(struct inode *dir, struct page **p)
> +/*
> + * Return the '..' directory entry and the page in which the entry was found
> + * (as a parameter - p).
> + *
> + * On Success ufs_put_page() should be called on *p.
> + *
> + * NOTE: Calls to ufs_get_page()/ufs_put_page() must be nested according to
> + * the rules documented in kmap_local_page()/kunmap_local().
> + *
> + * ufs_find_entry() and ufs_dotdot() act as calls to ufs_get_page() and
> + * must be treated accordingly for nesting purposes.
> + */
> +struct ufs_dir_entry *ufs_dotdot(struct inode *dir, struct page **p, void **pa)
>  {
> -	struct page *page = ufs_get_page(dir, 0);
> +	void *page_addr;
> +	struct page *page = ufs_get_page(dir, 0, &page_addr);
>  	struct ufs_dir_entry *de = NULL;
>  
>  	if (!IS_ERR(page)) {
>  		de = ufs_next_entry(dir->i_sb,
> -				    (struct ufs_dir_entry *)page_address(page));
> +				    (struct ufs_dir_entry *)page_addr);
>  		*p = page;
> +		*pa = page_addr;
>  	}
>  	return de;
>  }
> @@ -246,9 +267,17 @@ struct ufs_dir_entry *ufs_dotdot(struct inode *dir, struct page **p)
>   * returns the page in which the entry was found, and the entry itself
>   * (as a parameter - res_dir). Page is returned mapped and unlocked.
>   * Entry is guaranteed to be valid.
> + *
> + * On Success ufs_put_page() should be called on *res_page.
> + *
> + * NOTE: Calls to ufs_get_page()/ufs_put_page() must be nested according to
> + * the rules documented in kmap_local_page()/kunmap_local().
> + *
> + * ufs_find_entry() and ufs_dotdot() act as calls to ufs_get_page() and
> + * must be treated accordingly for nesting purposes.
>   */
>  struct ufs_dir_entry *ufs_find_entry(struct inode *dir, const struct qstr *qstr,
> -				     struct page **res_page)
> +				     struct page **res_page, void **res_page_addr)
>  {
>  	struct super_block *sb = dir->i_sb;
>  	const unsigned char *name = qstr->name;
> @@ -259,6 +288,7 @@ struct ufs_dir_entry *ufs_find_entry(struct inode *dir, const struct qstr *qstr,
>  	struct page *page = NULL;
>  	struct ufs_inode_info *ui = UFS_I(dir);
>  	struct ufs_dir_entry *de;
> +	void *page_addr;
>  
>  	UFSD("ENTER, dir_ino %lu, name %s, namlen %u\n", dir->i_ino, name, namelen);
>  
> @@ -267,6 +297,7 @@ struct ufs_dir_entry *ufs_find_entry(struct inode *dir, const struct qstr *qstr,
>  
>  	/* OFFSET_CACHE */
>  	*res_page = NULL;
> +	*res_page_addr = NULL;
>  
>  	start = ui->i_dir_start_lookup;
>  
> @@ -275,9 +306,10 @@ struct ufs_dir_entry *ufs_find_entry(struct inode *dir, const struct qstr *qstr,
>  	n = start;
>  	do {
>  		char *kaddr;
> -		page = ufs_get_page(dir, n);
> +
> +		page = ufs_get_page(dir, n, &page_addr);
>  		if (!IS_ERR(page)) {
> -			kaddr = page_address(page);
> +			kaddr = page_addr;
>  			de = (struct ufs_dir_entry *) kaddr;
>  			kaddr += ufs_last_byte(dir, n) - reclen;
>  			while ((char *) de <= kaddr) {
> @@ -285,7 +317,7 @@ struct ufs_dir_entry *ufs_find_entry(struct inode *dir, const struct qstr *qstr,
>  					goto found;
>  				de = ufs_next_entry(sb, de);
>  			}
> -			ufs_put_page(page);
> +			ufs_put_page(page, page_addr);
>  		}
>  		if (++n >= npages)
>  			n = 0;
> @@ -295,6 +327,7 @@ struct ufs_dir_entry *ufs_find_entry(struct inode *dir, const struct qstr *qstr,
>  
>  found:
>  	*res_page = page;
> +	*res_page_addr = page_addr;
>  	ui->i_dir_start_lookup = n;
>  	return de;
>  }
> @@ -312,6 +345,7 @@ int ufs_add_link(struct dentry *dentry, struct inode *inode)
>  	const unsigned int chunk_size = UFS_SB(sb)->s_uspi->s_dirblksize;
>  	unsigned short rec_len, name_len;
>  	struct page *page = NULL;
> +	void *page_addr = NULL;
>  	struct ufs_dir_entry *de;
>  	unsigned long npages = dir_pages(dir);
>  	unsigned long n;
> @@ -329,12 +363,12 @@ int ufs_add_link(struct dentry *dentry, struct inode *inode)
>  	for (n = 0; n <= npages; n++) {
>  		char *dir_end;
>  
> -		page = ufs_get_page(dir, n);
> +		page = ufs_get_page(dir, n, &page_addr);
>  		err = PTR_ERR(page);
>  		if (IS_ERR(page))
>  			goto out;
>  		lock_page(page);
> -		kaddr = page_address(page);
> +		kaddr = page_addr;
>  		dir_end = kaddr + ufs_last_byte(dir, n);
>  		de = (struct ufs_dir_entry *)kaddr;
>  		kaddr += PAGE_SIZE - reclen;
> @@ -365,14 +399,14 @@ int ufs_add_link(struct dentry *dentry, struct inode *inode)
>  			de = (struct ufs_dir_entry *) ((char *) de + rec_len);
>  		}
>  		unlock_page(page);
> -		ufs_put_page(page);
> +		ufs_put_page(page, page_addr);
>  	}
>  	BUG();
>  	return -EINVAL;
>  
>  got_it:
>  	pos = page_offset(page) +
> -			(char*)de - (char*)page_address(page);
> +			(char *)de - (char *)page_addr;
>  	err = ufs_prepare_chunk(page, pos, rec_len);
>  	if (err)
>  		goto out_unlock;
> @@ -396,7 +430,7 @@ int ufs_add_link(struct dentry *dentry, struct inode *inode)
>  	mark_inode_dirty(dir);
>  	/* OFFSET_CACHE */
>  out_put:
> -	ufs_put_page(page);
> +	ufs_put_page(page, page_addr);
>  out:
>  	return err;
>  out_unlock:
> @@ -441,7 +475,7 @@ ufs_readdir(struct file *file, struct dir_context *ctx)
>  		char *kaddr, *limit;
>  		struct ufs_dir_entry *de;
>  
> -		struct page *page = ufs_get_page(inode, n);
> +		struct page *page = ufs_get_page(inode, n, (void **)&kaddr);
>  
>  		if (IS_ERR(page)) {
>  			ufs_error(sb, __func__,
> @@ -450,7 +484,6 @@ ufs_readdir(struct file *file, struct dir_context *ctx)
>  			ctx->pos += PAGE_SIZE - offset;
>  			return -EIO;
>  		}
> -		kaddr = page_address(page);
>  		if (unlikely(need_revalidate)) {
>  			if (offset) {
>  				offset = ufs_validate_entry(sb, kaddr, offset, chunk_mask);
> @@ -476,13 +509,13 @@ ufs_readdir(struct file *file, struct dir_context *ctx)
>  					       ufs_get_de_namlen(sb, de),
>  					       fs32_to_cpu(sb, de->d_ino),
>  					       d_type)) {
> -					ufs_put_page(page);
> +					ufs_put_page(page, kaddr);
>  					return 0;
>  				}
>  			}
>  			ctx->pos += fs16_to_cpu(sb, de->d_reclen);
>  		}
> -		ufs_put_page(page);
> +		ufs_put_page(page, kaddr);
>  	}
>  	return 0;
>  }
> @@ -493,10 +526,9 @@ ufs_readdir(struct file *file, struct dir_context *ctx)
>   * previous entry.
>   */
>  int ufs_delete_entry(struct inode *inode, struct ufs_dir_entry *dir,
> -		     struct page * page)
> +		     struct page *page, char *kaddr)
>  {
>  	struct super_block *sb = inode->i_sb;
> -	char *kaddr = page_address(page);
>  	unsigned from = ((char*)dir - kaddr) & ~(UFS_SB(sb)->s_uspi->s_dirblksize - 1);
>  	unsigned to = ((char*)dir - kaddr) + fs16_to_cpu(sb, dir->d_reclen);
>  	loff_t pos;
> @@ -522,7 +554,7 @@ int ufs_delete_entry(struct inode *inode, struct ufs_dir_entry *dir,
>  		de = ufs_next_entry(sb, de);
>  	}
>  	if (pde)
> -		from = (char*)pde - (char*)page_address(page);
> +		from = (char *)pde - kaddr;
>  
>  	pos = page_offset(page) + from;
>  	lock_page(page);
> @@ -535,7 +567,7 @@ int ufs_delete_entry(struct inode *inode, struct ufs_dir_entry *dir,
>  	inode->i_ctime = inode->i_mtime = current_time(inode);
>  	mark_inode_dirty(inode);
>  out:
> -	ufs_put_page(page);
> +	ufs_put_page(page, kaddr);
>  	UFSD("EXIT\n");
>  	return err;
>  }
> @@ -559,8 +591,7 @@ int ufs_make_empty(struct inode * inode, struct inode *dir)
>  		goto fail;
>  	}
>  
> -	kmap(page);
> -	base = (char*)page_address(page);
> +	base = kmap_local_page(page);
>  	memset(base, 0, PAGE_SIZE);
>  
>  	de = (struct ufs_dir_entry *) base;
> @@ -577,7 +608,7 @@ int ufs_make_empty(struct inode * inode, struct inode *dir)
>  	de->d_reclen = cpu_to_fs16(sb, chunk_size - UFS_DIR_REC_LEN(1));
>  	ufs_set_de_namlen(sb, de, 2);
>  	strcpy (de->d_name, "..");
> -	kunmap(page);
> +	kunmap_local(base);
>  
>  	err = ufs_commit_chunk(page, 0, chunk_size);
>  fail:
> @@ -592,17 +623,18 @@ int ufs_empty_dir(struct inode * inode)
>  {
>  	struct super_block *sb = inode->i_sb;
>  	struct page *page = NULL;
> +	void *page_addr;
>  	unsigned long i, npages = dir_pages(inode);
>  
>  	for (i = 0; i < npages; i++) {
>  		char *kaddr;
>  		struct ufs_dir_entry *de;
> -		page = ufs_get_page(inode, i);
>  
> +		page = ufs_get_page(inode, i, &page_addr);
>  		if (IS_ERR(page))
>  			continue;
>  
> -		kaddr = page_address(page);
> +		kaddr = page_addr;
>  		de = (struct ufs_dir_entry *)kaddr;
>  		kaddr += ufs_last_byte(inode, i) - UFS_DIR_REC_LEN(1);
>  
> @@ -629,12 +661,12 @@ int ufs_empty_dir(struct inode * inode)
>  			}
>  			de = ufs_next_entry(sb, de);
>  		}
> -		ufs_put_page(page);
> +		ufs_put_page(page, page_addr);
>  	}
>  	return 1;
>  
>  not_empty:
> -	ufs_put_page(page);
> +	ufs_put_page(page, page_addr);
>  	return 0;
>  }
>  
> diff --git a/fs/ufs/namei.c b/fs/ufs/namei.c
> index 29d5a0e0c8f0..bc7060d10dd2 100644
> --- a/fs/ufs/namei.c
> +++ b/fs/ufs/namei.c
> @@ -210,13 +210,14 @@ static int ufs_unlink(struct inode *dir, struct dentry *dentry)
>  	struct inode * inode = d_inode(dentry);
>  	struct ufs_dir_entry *de;
>  	struct page *page;
> +	void *page_addr;
>  	int err = -ENOENT;
>  
> -	de = ufs_find_entry(dir, &dentry->d_name, &page);
> +	de = ufs_find_entry(dir, &dentry->d_name, &page, &page_addr);
>  	if (!de)
>  		goto out;
>  
> -	err = ufs_delete_entry(dir, de, page);
> +	err = ufs_delete_entry(dir, de, page, page_addr);
>  	if (err)
>  		goto out;
>  
> @@ -250,27 +251,31 @@ static int ufs_rename(struct user_namespace *mnt_userns, struct inode *old_dir,
>  	struct inode *old_inode = d_inode(old_dentry);
>  	struct inode *new_inode = d_inode(new_dentry);
>  	struct page *dir_page = NULL;
> +	void *dir_page_addr;
>  	struct ufs_dir_entry * dir_de = NULL;
>  	struct page *old_page;
> +	void *old_page_addr;
>  	struct ufs_dir_entry *old_de;
>  	int err = -ENOENT;
>  
>  	if (flags & ~RENAME_NOREPLACE)
>  		return -EINVAL;
>  
> -	old_de = ufs_find_entry(old_dir, &old_dentry->d_name, &old_page);
> +	old_de = ufs_find_entry(old_dir, &old_dentry->d_name, &old_page,
> +				&old_page_addr);
>  	if (!old_de)
>  		goto out;
>  
>  	if (S_ISDIR(old_inode->i_mode)) {
>  		err = -EIO;
> -		dir_de = ufs_dotdot(old_inode, &dir_page);
> +		dir_de = ufs_dotdot(old_inode, &dir_page, &dir_page_addr);
>  		if (!dir_de)
>  			goto out_old;
>  	}
>  
>  	if (new_inode) {
>  		struct page *new_page;
> +		void *page_addr;

Nit:

It might be good to make this new_page_addr to keep it straight with the other
pages mapped in this function.

Regardless:

Reviewed-by: Ira Weiny <ira.weiny@intel.com>

>  		struct ufs_dir_entry *new_de;
>  
>  		err = -ENOTEMPTY;
> @@ -278,10 +283,11 @@ static int ufs_rename(struct user_namespace *mnt_userns, struct inode *old_dir,
>  			goto out_dir;
>  
>  		err = -ENOENT;
> -		new_de = ufs_find_entry(new_dir, &new_dentry->d_name, &new_page);
> +		new_de = ufs_find_entry(new_dir, &new_dentry->d_name, &new_page,
> +					&page_addr);
>  		if (!new_de)
>  			goto out_dir;
> -		ufs_set_link(new_dir, new_de, new_page, old_inode, 1);
> +		ufs_set_link(new_dir, new_de, new_page, page_addr, old_inode, 1);
>  		new_inode->i_ctime = current_time(new_inode);
>  		if (dir_de)
>  			drop_nlink(new_inode);
> @@ -300,29 +306,25 @@ static int ufs_rename(struct user_namespace *mnt_userns, struct inode *old_dir,
>  	 */
>  	old_inode->i_ctime = current_time(old_inode);
>  
> -	ufs_delete_entry(old_dir, old_de, old_page);
> +	ufs_delete_entry(old_dir, old_de, old_page, old_page_addr);
>  	mark_inode_dirty(old_inode);
>  
>  	if (dir_de) {
>  		if (old_dir != new_dir)
> -			ufs_set_link(old_inode, dir_de, dir_page, new_dir, 0);
> -		else {
> -			kunmap(dir_page);
> -			put_page(dir_page);
> -		}
> +			ufs_set_link(old_inode, dir_de, dir_page,
> +				     dir_page_addr, new_dir, 0);
> +		else
> +			ufs_put_page(dir_page, dir_page_addr);
>  		inode_dec_link_count(old_dir);
>  	}
>  	return 0;
>  
>  
>  out_dir:
> -	if (dir_de) {
> -		kunmap(dir_page);
> -		put_page(dir_page);
> -	}
> +	if (dir_de)
> +		ufs_put_page(dir_page, dir_page_addr);
>  out_old:
> -	kunmap(old_page);
> -	put_page(old_page);
> +	ufs_put_page(old_page, old_page_addr);
>  out:
>  	return err;
>  }
> diff --git a/fs/ufs/ufs.h b/fs/ufs/ufs.h
> index 550f7c5a3636..20d224c163ab 100644
> --- a/fs/ufs/ufs.h
> +++ b/fs/ufs/ufs.h
> @@ -102,12 +102,16 @@ extern const struct inode_operations ufs_dir_inode_operations;
>  extern int ufs_add_link (struct dentry *, struct inode *);
>  extern ino_t ufs_inode_by_name(struct inode *, const struct qstr *);
>  extern int ufs_make_empty(struct inode *, struct inode *);
> -extern struct ufs_dir_entry *ufs_find_entry(struct inode *, const struct qstr *, struct page **);
> -extern int ufs_delete_entry(struct inode *, struct ufs_dir_entry *, struct page *);
> +extern struct ufs_dir_entry *ufs_find_entry(struct inode *dir, const struct qstr *qstr,
> +					    struct page **res_page, void **res_page_addr);
> +extern int ufs_delete_entry(struct inode *inode, struct ufs_dir_entry *dir,
> +			    struct page *page, char *kaddr);
>  extern int ufs_empty_dir (struct inode *);
> -extern struct ufs_dir_entry *ufs_dotdot(struct inode *, struct page **);
> +extern struct ufs_dir_entry *ufs_dotdot(struct inode *dir, struct page **p, void **pa);
>  extern void ufs_set_link(struct inode *dir, struct ufs_dir_entry *de,
> -			 struct page *page, struct inode *inode, bool update_times);
> +			 struct page *page, void *page_addr,
> +			 struct inode *inode, bool update_times);
> +extern void ufs_put_page(struct page *page, void *page_addr);
>  
>  /* file.c */
>  extern const struct inode_operations ufs_file_inode_operations;
> -- 
> 2.34.1
>