Commit 782b76d7 authored by Ira Weiny's avatar Ira Weiny Committed by Jan Kara
Browse files

fs/ext2: Replace kmap() with kmap_local_page() 

The k[un]map() calls in ext2_[get|put]_page() are localized to a single
thread.  kmap_local_page() is more efficient.

Replace the kmap/kunmap calls with kmap_local_page()/kunmap_local().
kunmap_local() requires the mapping address so return that address from
ext2_get_page() to be used in ext2_put_page().  This works well because
many of the callers need the address anyway so it is not bad to return
it along with the page.

In addition, kmap_local_page()/kunmap_local() require strict nesting
rules to be followed.

Document the new nesting requirements of ext2_get_page() and
ext2_put_page() as well as the relationship between ext2_get_page(),
ext2_find_entry(), and ext2_dotdot().

Adjust one ext2_put_page() call site in ext2_rename() to ensure the new
nesting requirements are met.

Finally, adjust code style for checkpatch.

To: Jan Kara <jack@suse.com>
Link: https://lore.kernel.org/r/20210329065402.3297092-3-ira.weiny@intel.com


Signed-off-by: default avatarIra Weiny <ira.weiny@intel.com>
Signed-off-by: default avatarJan Kara <jack@suse.cz>
parent e2ebb123

fs/ext2/dir.c

+59 −30
Original line number Diff line number Diff line
@@ -190,13 +190,20 @@ static bool ext2_check_page(struct page *page, int quiet) 
	return false;

}



/*

 * Calls to ext2_get_page()/ext2_put_page() must be nested according to the

 * rules documented in kmap_local_page()/kunmap_local().

 *

 * NOTE: ext2_find_entry() and ext2_dotdot() act as a call to ext2_get_page()

 * and should be treated as a call to ext2_get_page() for nesting purposes.

 */

static struct page * ext2_get_page(struct inode *dir, unsigned long n,

				   int quiet)

				   int quiet, 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) || !ext2_check_page(page, quiet))

				goto fail;
@@ -205,7 +212,7 @@ static struct page * ext2_get_page(struct inode *dir, unsigned long n, 
	return page;



fail:

	ext2_put_page(page);

	ext2_put_page(page, *page_addr);

	return ERR_PTR(-EIO);

}
@@ -276,7 +283,7 @@ ext2_readdir(struct file *file, struct dir_context *ctx) 
	for ( ; n < npages; n++, offset = 0) {

		char *kaddr, *limit;

		ext2_dirent *de;

		struct page *page = ext2_get_page(inode, n, 0);

		struct page *page = ext2_get_page(inode, n, 0, (void **)&kaddr);



		if (IS_ERR(page)) {

			ext2_error(sb, __func__,
@@ -285,7 +292,6 @@ ext2_readdir(struct file *file, struct dir_context *ctx) 
			ctx->pos += PAGE_SIZE - offset;

			return PTR_ERR(page);

		}

		kaddr = page_address(page);

		if (unlikely(need_revalidate)) {

			if (offset) {

				offset = ext2_validate_entry(kaddr, offset, chunk_mask);
@@ -300,7 +306,7 @@ ext2_readdir(struct file *file, struct dir_context *ctx) 
			if (de->rec_len == 0) {

				ext2_error(sb, __func__,

					"zero-length directory entry");

				ext2_put_page(page);

				ext2_put_page(page, kaddr);

				return -EIO;

			}

			if (de->inode) {
@@ -312,13 +318,13 @@ ext2_readdir(struct file *file, struct dir_context *ctx) 
				if (!dir_emit(ctx, de->name, de->name_len,

						le32_to_cpu(de->inode),

						d_type)) {

					ext2_put_page(page);

					ext2_put_page(page, kaddr);

					return 0;

				}

			}

			ctx->pos += ext2_rec_len_from_disk(de->rec_len);

		}

		ext2_put_page(page);

		ext2_put_page(page, kaddr);

	}

	return 0;

}
@@ -332,9 +338,16 @@ ext2_readdir(struct file *file, struct dir_context *ctx) 
 * Entry is guaranteed to be valid.

 *

 * On Success ext2_put_page() should be called on *res_page.

 *

 * NOTE: Calls to ext2_get_page()/ext2_put_page() must be nested according to

 * the rules documented in kmap_local_page()/kunmap_local().

 *

 * ext2_find_entry() and ext2_dotdot() act as a call to ext2_get_page() and

 * should be treated as a call to ext2_get_page() for nesting purposes.

 */

struct ext2_dir_entry_2 *ext2_find_entry (struct inode *dir,

			const struct qstr *child, struct page **res_page)

			const struct qstr *child, struct page **res_page,

			void **res_page_addr)

{

	const char *name = child->name;

	int namelen = child->len;
@@ -344,12 +357,14 @@ struct ext2_dir_entry_2 *ext2_find_entry (struct inode *dir, 
	struct page *page = NULL;

	struct ext2_inode_info *ei = EXT2_I(dir);

	ext2_dirent * de;

	void *page_addr;



	if (npages == 0)

		goto out;



	/* OFFSET_CACHE */

	*res_page = NULL;

	*res_page_addr = NULL;



	start = ei->i_dir_start_lookup;

	if (start >= npages)
@@ -357,25 +372,25 @@ struct ext2_dir_entry_2 *ext2_find_entry (struct inode *dir, 
	n = start;

	do {

		char *kaddr;

		page = ext2_get_page(dir, n, 0);

		page = ext2_get_page(dir, n, 0, &page_addr);

		if (IS_ERR(page))

			return ERR_CAST(page);



		kaddr = page_address(page);

		kaddr = page_addr;

		de = (ext2_dirent *) kaddr;

		kaddr += ext2_last_byte(dir, n) - reclen;

		while ((char *) de <= kaddr) {

			if (de->rec_len == 0) {

				ext2_error(dir->i_sb, __func__,

					"zero-length directory entry");

				ext2_put_page(page);

				ext2_put_page(page, page_addr);

				goto out;

			}

			if (ext2_match(namelen, name, de))

				goto found;

			de = ext2_next_entry(de);

		}

		ext2_put_page(page);

		ext2_put_page(page, page_addr);



		if (++n >= npages)

			n = 0;
@@ -393,6 +408,7 @@ struct ext2_dir_entry_2 *ext2_find_entry (struct inode *dir, 


found:

	*res_page = page;

	*res_page_addr = page_addr;

	ei->i_dir_start_lookup = n;

	return de;

}
@@ -402,15 +418,24 @@ struct ext2_dir_entry_2 *ext2_find_entry (struct inode *dir, 
 * (as a parameter - p).

 *

 * On Success ext2_put_page() should be called on *p.

 *

 * NOTE: Calls to ext2_get_page()/ext2_put_page() must be nested according to

 * the rules documented in kmap_local_page()/kunmap_local().

 *

 * ext2_find_entry() and ext2_dotdot() act as a call to ext2_get_page() and

 * should be treated as a call to ext2_get_page() for nesting purposes.

 */

struct ext2_dir_entry_2 * ext2_dotdot (struct inode *dir, struct page **p)

struct ext2_dir_entry_2 *ext2_dotdot(struct inode *dir, struct page **p,

				     void **pa)

{

	struct page *page = ext2_get_page(dir, 0, 0);

	void *page_addr;

	struct page *page = ext2_get_page(dir, 0, 0, &page_addr);

	ext2_dirent *de = NULL;



	if (!IS_ERR(page)) {

		de = ext2_next_entry((ext2_dirent *) page_address(page));

		de = ext2_next_entry((ext2_dirent *) page_addr);

		*p = page;

		*pa = page_addr;

	}

	return de;

}
@@ -419,13 +444,14 @@ int ext2_inode_by_name(struct inode *dir, const struct qstr *child, ino_t *ino) 
{

	struct ext2_dir_entry_2 *de;

	struct page *page;

	void *page_addr;

	

	de = ext2_find_entry(dir, child, &page);

	de = ext2_find_entry(dir, child, &page, &page_addr);

	if (IS_ERR(de))

		return PTR_ERR(de);



	*ino = le32_to_cpu(de->inode);

	ext2_put_page(page);

	ext2_put_page(page, page_addr);

	return 0;

}
@@ -435,10 +461,11 @@ static int ext2_prepare_chunk(struct page *page, loff_t pos, unsigned len) 
}



void ext2_set_link(struct inode *dir, struct ext2_dir_entry_2 *de,

		   struct page *page, struct inode *inode, int update_times)

		   struct page *page, void *page_addr, struct inode *inode,

		   int update_times)

{

	loff_t pos = page_offset(page) +

			(char *) de - (char *) page_address(page);

			(char *) de - (char *) page_addr;

	unsigned len = ext2_rec_len_from_disk(de->rec_len);

	int err;
@@ -466,10 +493,10 @@ int ext2_add_link (struct dentry *dentry, struct inode *inode) 
	unsigned reclen = EXT2_DIR_REC_LEN(namelen);

	unsigned short rec_len, name_len;

	struct page *page = NULL;

	void *page_addr = NULL;

	ext2_dirent * de;

	unsigned long npages = dir_pages(dir);

	unsigned long n;

	char *kaddr;

	loff_t pos;

	int err;
@@ -479,14 +506,15 @@ int ext2_add_link (struct dentry *dentry, struct inode *inode) 
	 * to protect that region.

	 */

	for (n = 0; n <= npages; n++) {

		char *kaddr;

		char *dir_end;



		page = ext2_get_page(dir, n, 0);

		page = ext2_get_page(dir, n, 0, &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 + ext2_last_byte(dir, n);

		de = (ext2_dirent *)kaddr;

		kaddr += PAGE_SIZE - reclen;
@@ -517,14 +545,14 @@ int ext2_add_link (struct dentry *dentry, struct inode *inode) 
			de = (ext2_dirent *) ((char *) de + rec_len);

		}

		unlock_page(page);

		ext2_put_page(page);

		ext2_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 = ext2_prepare_chunk(page, pos, rec_len);

	if (err)

		goto out_unlock;
@@ -544,7 +572,7 @@ int ext2_add_link (struct dentry *dentry, struct inode *inode) 
	mark_inode_dirty(dir);

	/* OFFSET_CACHE */

out_put:

	ext2_put_page(page);

	ext2_put_page(page, page_addr);

out:

	return err;

out_unlock:
@@ -641,6 +669,7 @@ int ext2_make_empty(struct inode *inode, struct inode *parent) 
 */

int ext2_empty_dir (struct inode * inode)

{

	void *page_addr = NULL;

	struct page *page = NULL;

	unsigned long i, npages = dir_pages(inode);

	int dir_has_error = 0;
@@ -648,14 +677,14 @@ int ext2_empty_dir (struct inode * inode) 
	for (i = 0; i < npages; i++) {

		char *kaddr;

		ext2_dirent * de;

		page = ext2_get_page(inode, i, dir_has_error);

		page = ext2_get_page(inode, i, dir_has_error, &page_addr);



		if (IS_ERR(page)) {

			dir_has_error = 1;

			continue;

		}



		kaddr = page_address(page);

		kaddr = page_addr;

		de = (ext2_dirent *)kaddr;

		kaddr += ext2_last_byte(inode, i) - EXT2_DIR_REC_LEN(1);
@@ -681,12 +710,12 @@ int ext2_empty_dir (struct inode * inode) 
			}

			de = ext2_next_entry(de);

		}

		ext2_put_page(page);

		ext2_put_page(page, page_addr);

	}

	return 1;



not_empty:

	ext2_put_page(page);

	ext2_put_page(page, page_addr);

	return 0;

}

fs/ext2/ext2.h

+7 −5
Original line number Diff line number Diff line
@@ -742,14 +742,16 @@ extern int ext2_add_link (struct dentry *, struct inode *); 
extern int ext2_inode_by_name(struct inode *dir,

			      const struct qstr *child, ino_t *ino);

extern int ext2_make_empty(struct inode *, struct inode *);

extern struct ext2_dir_entry_2 * ext2_find_entry (struct inode *,const struct qstr *, struct page **);

extern struct ext2_dir_entry_2 *ext2_find_entry(struct inode *, const struct qstr *,

						struct page **, void **res_page_addr);

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)

extern struct ext2_dir_entry_2 *ext2_dotdot(struct inode *dir, struct page **p, void **pa);

extern void ext2_set_link(struct inode *, struct ext2_dir_entry_2 *, struct page *, void *,

			  struct inode *, int);

static inline void ext2_put_page(struct page *page, void *page_addr)

{

	kunmap(page);

	kunmap_local(page_addr);

	put_page(page);

}

fs/ext2/namei.c

+21 −14
Original line number Diff line number Diff line
@@ -281,20 +281,21 @@ static int ext2_unlink(struct inode * dir, struct dentry *dentry) 
	struct inode * inode = d_inode(dentry);

	struct ext2_dir_entry_2 * de;

	struct page * page;

	void *page_addr;

	int err;



	err = dquot_initialize(dir);

	if (err)

		goto out;



	de = ext2_find_entry(dir, &dentry->d_name, &page);

	de = ext2_find_entry(dir, &dentry->d_name, &page, &page_addr);

	if (IS_ERR(de)) {

		err = PTR_ERR(de);

		goto out;

	}



	err = ext2_delete_entry (de, page);

	ext2_put_page(page);

	ext2_put_page(page, page_addr);

	if (err)

		goto out;
@@ -329,8 +330,10 @@ static int ext2_rename (struct user_namespace * mnt_userns, 
	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 ext2_dir_entry_2 * dir_de = NULL;

	struct page * old_page;

	void *old_page_addr;

	struct ext2_dir_entry_2 * old_de;

	int err;
@@ -345,7 +348,8 @@ static int ext2_rename (struct user_namespace * mnt_userns, 
	if (err)

		goto out;



	old_de = ext2_find_entry(old_dir, &old_dentry->d_name, &old_page);

	old_de = ext2_find_entry(old_dir, &old_dentry->d_name, &old_page,

				 &old_page_addr);

	if (IS_ERR(old_de)) {

		err = PTR_ERR(old_de);

		goto out;
@@ -353,12 +357,13 @@ static int ext2_rename (struct user_namespace * mnt_userns, 


	if (S_ISDIR(old_inode->i_mode)) {

		err = -EIO;

		dir_de = ext2_dotdot(old_inode, &dir_page);

		dir_de = ext2_dotdot(old_inode, &dir_page, &dir_page_addr);

		if (!dir_de)

			goto out_old;

	}



	if (new_inode) {

		void *page_addr;

		struct page *new_page;

		struct ext2_dir_entry_2 *new_de;
@@ -366,13 +371,14 @@ static int ext2_rename (struct user_namespace * mnt_userns, 
		if (dir_de && !ext2_empty_dir (new_inode))

			goto out_dir;



		new_de = ext2_find_entry(new_dir, &new_dentry->d_name, &new_page);

		new_de = ext2_find_entry(new_dir, &new_dentry->d_name,

					 &new_page, &page_addr);

		if (IS_ERR(new_de)) {

			err = PTR_ERR(new_de);

			goto out_dir;

		}

		ext2_set_link(new_dir, new_de, new_page, old_inode, 1);

		ext2_put_page(new_page);

		ext2_set_link(new_dir, new_de, new_page, page_addr, old_inode, 1);

		ext2_put_page(new_page, page_addr);

		new_inode->i_ctime = current_time(new_inode);

		if (dir_de)

			drop_nlink(new_inode);
@@ -393,23 +399,24 @@ static int ext2_rename (struct user_namespace * mnt_userns, 
	mark_inode_dirty(old_inode);



	ext2_delete_entry(old_de, old_page);

	ext2_put_page(old_page);



	if (dir_de) {

		if (old_dir != new_dir)

			ext2_set_link(old_inode, dir_de, dir_page, new_dir, 0);

			ext2_set_link(old_inode, dir_de, dir_page,

				      dir_page_addr, new_dir, 0);



		ext2_put_page(dir_page);

		ext2_put_page(dir_page, dir_page_addr);

		inode_dec_link_count(old_dir);

	}

	return 0;



	ext2_put_page(old_page, old_page_addr);

	return 0;



out_dir:

	if (dir_de)

		ext2_put_page(dir_page);

		ext2_put_page(dir_page, dir_page_addr);

out_old:

	ext2_put_page(old_page);

	ext2_put_page(old_page, old_page_addr);

out:

	return err;

}