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Date:   Mon, 22 Mar 2021 17:49:48 -0700
From:   Ira Weiny <ira.weiny@intel.com>
To:     Jan Kara <jack@suse.com>, linux-ext4@vger.kernel.org
Cc:     linux-kernel@vger.kernel.org
Subject: ext2_set_link()->ext2_put_page() question
Message-ID: <20210323004948.GR3014244@iweiny-DESK2.sc.intel.com>
MIME-Version: 1.0
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Content-Description: iff --git a/fs/ext2/dir.c b/fs/ext2/dir.ciff --git a/fs/ext2/dir.c b/fs/ext2/dir.c
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User-Agent: Mutt/1.11.1 (2018-12-01)
Precedence: bulk

Jan,

Why does ext2_set_link() need to call ext2_put_page()?

I don't see any reason that we could not match up the ext2_put_page() calls
with the ext2_find_entry().

Similarly am I missing something by moving the ext2_put_page() out of
ext2_delete_entry()?

See below patch.

I'm in the process of changing the kmap() calls in ext2_[get|put]_page() into
kmap_local_page() and I noticed this imbalance.  It does not really save me
anything because I need to pass the kaddr into these calls but IMO it makes the
code a bit easier to follow.

If you agree I will get a patch together to submit with the kmap_local_page()
patch.

Thanks,
Ira


17:29:44 > git di
diff --git a/fs/ext2/dir.c b/fs/ext2/dir.c
index 14aa45316ad2..bd572cead638 100644
--- a/fs/ext2/dir.c
+++ b/fs/ext2/dir.c
@@ -449,7 +449,6 @@ void ext2_set_link(struct inode *dir, struct ext2_dir_entry_2 *de,
        de->inode = cpu_to_le32(inode->i_ino);
        ext2_set_de_type(de, inode);
        err = ext2_commit_chunk(page, pos, len);
-       ext2_put_page(page);
        if (update_times)
                dir->i_mtime = dir->i_ctime = current_time(dir);
        EXT2_I(dir)->i_flags &= ~EXT2_BTREE_FL;
@@ -594,7 +593,6 @@ int ext2_delete_entry (struct ext2_dir_entry_2 * dir, struct page * page )
        EXT2_I(inode)->i_flags &= ~EXT2_BTREE_FL;
        mark_inode_dirty(inode);
 out:
-       ext2_put_page(page);
        return err;
 }
 
diff --git a/fs/ext2/namei.c b/fs/ext2/namei.c
index 3367384d344d..a841b00c6828 100644
--- a/fs/ext2/namei.c
+++ b/fs/ext2/namei.c
@@ -371,6 +371,7 @@ static int ext2_rename (struct user_namespace * mnt_userns,
                        goto out_dir;
                }
                ext2_set_link(new_dir, new_de, new_page, old_inode, 1);
+               ext2_put_page(new_page);
                new_inode->i_ctime = current_time(new_inode);
                if (dir_de)
                        drop_nlink(new_inode);
@@ -391,12 +392,13 @@ 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);
-               else
-                       ext2_put_page(dir_page);
+
+               ext2_put_page(dir_page);
                inode_dec_link_count(old_dir);
        }
        return 0;

17:35:41 > git di
diff --git a/fs/ext2/dir.c b/fs/ext2/dir.c
index 14aa45316ad2..bd572cead638 100644
--- a/fs/ext2/dir.c
+++ b/fs/ext2/dir.c
@@ -449,7 +449,6 @@ void ext2_set_link(struct inode *dir, struct ext2_dir_entry_2 *de,
        de->inode = cpu_to_le32(inode->i_ino);
        ext2_set_de_type(de, inode);
        err = ext2_commit_chunk(page, pos, len);
-       ext2_put_page(page);
        if (update_times)
                dir->i_mtime = dir->i_ctime = current_time(dir);
        EXT2_I(dir)->i_flags &= ~EXT2_BTREE_FL;
@@ -594,7 +593,6 @@ int ext2_delete_entry (struct ext2_dir_entry_2 * dir, struct page * page )
        EXT2_I(inode)->i_flags &= ~EXT2_BTREE_FL;
        mark_inode_dirty(inode);
 out:
-       ext2_put_page(page);
        return err;
 }
 
diff --git a/fs/ext2/namei.c b/fs/ext2/namei.c
index 3367384d344d..7af9ab3f975e 100644
--- a/fs/ext2/namei.c
+++ b/fs/ext2/namei.c
@@ -294,6 +294,7 @@ static int ext2_unlink(struct inode * dir, struct dentry *dentry)
        }
 
        err = ext2_delete_entry (de, page);
+       ext2_put_page(page);
        if (err)
                goto out;
 
@@ -371,6 +372,7 @@ static int ext2_rename (struct user_namespace * mnt_userns,
                        goto out_dir;
                }
                ext2_set_link(new_dir, new_de, new_page, old_inode, 1);
+               ext2_put_page(new_page);
                new_inode->i_ctime = current_time(new_inode);
                if (dir_de)
                        drop_nlink(new_inode);
@@ -391,12 +393,13 @@ 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);
-               else
-                       ext2_put_page(dir_page);
+
+               ext2_put_page(dir_page);
                inode_dec_link_count(old_dir);
        }
        return 0;