ext2_put_page(): accept any pointer within the page

eliminates the need to keep the pointer to the first byte within
the page if we are guaranteed to have pointers to some byte
in the same page at hand.

Don't backport without commit 88d7b12 ("highmem: round down the
address passed to kunmap_flush_on_unmap()").

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Reviewed-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>
Tested-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>

Author: Al Viro

fs/ext2/dir.c

@@ -299,7 +299,7 @@ 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, kaddr);
+				ext2_put_page(page, de);
 				return -EIO;
 			}
 			if (de->inode) {
@@ -311,7 +311,7 @@ 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, kaddr);
+					ext2_put_page(page, de);
 					return 0;
 				}
 			}
@@ -377,14 +377,14 @@ struct ext2_dir_entry_2 *ext2_find_entry (struct inode *dir,
 			if (de->rec_len == 0) {
 				ext2_error(dir->i_sb, __func__,
 					"zero-length directory entry");
-				ext2_put_page(page, page_addr);
+				ext2_put_page(page, de);
 				goto out;
 			}
 			if (ext2_match(namelen, name, de))
 				goto found;
 			de = ext2_next_entry(de);
 		}
-		ext2_put_page(page, page_addr);
+		ext2_put_page(page, kaddr);
 
 		if (++n >= npages)
 			n = 0;
@@ -443,7 +443,7 @@ int ext2_inode_by_name(struct inode *dir, const struct qstr *child, ino_t *ino)
 		return PTR_ERR(de);
 
 	*ino = le32_to_cpu(de->inode);
-	ext2_put_page(page, page_addr);
+	ext2_put_page(page, de);
 	return 0;
 }
 
@@ -499,7 +499,6 @@ 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;
@@ -515,11 +514,10 @@ int ext2_add_link (struct dentry *dentry, struct inode *inode)
 		char *kaddr;
 		char *dir_end;
 
-		page_addr = ext2_get_page(dir, n, 0, &page);
-		if (IS_ERR(page_addr))
-			return PTR_ERR(page_addr);
+		kaddr = ext2_get_page(dir, n, 0, &page);
+		if (IS_ERR(kaddr))
+			return PTR_ERR(kaddr);
 		lock_page(page);
-		kaddr = page_addr;
 		dir_end = kaddr + ext2_last_byte(dir, n);
 		de = (ext2_dirent *)kaddr;
 		kaddr += PAGE_SIZE - reclen;
@@ -550,7 +548,7 @@ int ext2_add_link (struct dentry *dentry, struct inode *inode)
 			de = (ext2_dirent *) ((char *) de + rec_len);
 		}
 		unlock_page(page);
-		ext2_put_page(page, page_addr);
+		ext2_put_page(page, kaddr);
 	}
 	BUG();
 	return -EINVAL;
@@ -577,7 +575,7 @@ int ext2_add_link (struct dentry *dentry, struct inode *inode)
 	err = ext2_handle_dirsync(dir);
 	/* OFFSET_CACHE */
 out_put:
-	ext2_put_page(page, page_addr);
+	ext2_put_page(page, de);
 	return err;
 out_unlock:
 	unlock_page(page);
@@ -675,19 +673,17 @@ 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;
+	struct page *page;
+	char *kaddr;
 	unsigned long i, npages = dir_pages(inode);
 
 	for (i = 0; i < npages; i++) {
-		char *kaddr;
-		ext2_dirent * de;
-		page_addr = ext2_get_page(inode, i, 0, &page);
+		ext2_dirent *de;
 
-		if (IS_ERR(page_addr))
+		kaddr = ext2_get_page(inode, i, 0, &page);
+		if (IS_ERR(kaddr))
 			return 0;
 
-		kaddr = page_addr;
 		de = (ext2_dirent *)kaddr;
 		kaddr += ext2_last_byte(inode, i) - EXT2_DIR_REC_LEN(1);
 
@@ -713,12 +709,12 @@ int ext2_empty_dir (struct inode * inode)
 			}
 			de = ext2_next_entry(de);
 		}
-		ext2_put_page(page, page_addr);
+		ext2_put_page(page, kaddr);
 	}
 	return 1;
 
 not_empty:
-	ext2_put_page(page, page_addr);
+	ext2_put_page(page, kaddr);
 	return 0;
 }
 

fs/ext2/namei.c

@@ -288,7 +288,7 @@ static int ext2_unlink(struct inode * dir, struct dentry *dentry)
 	}
 
 	err = ext2_delete_entry (de, page, page_addr);
-	ext2_put_page(page, page_addr);
+	ext2_put_page(page, de);
 	if (err)
 		goto out;
 
@@ -370,7 +370,7 @@ static int ext2_rename (struct mnt_idmap * idmap,
 		}
 		err = ext2_set_link(new_dir, new_de, new_page, page_addr,
 				    old_inode, true);
-		ext2_put_page(new_page, page_addr);
+		ext2_put_page(new_page, new_de);
 		if (err)
 			goto out_dir;
 		new_inode->i_ctime = current_time(new_inode);
@@ -402,9 +402,9 @@ static int ext2_rename (struct mnt_idmap * idmap,
 	}
 out_dir:
 	if (dir_de)
-		ext2_put_page(dir_page, dir_page_addr);
+		ext2_put_page(dir_page, dir_de);
 out_old:
-	ext2_put_page(old_page, old_page_addr);
+	ext2_put_page(old_page, old_de);
 	return err;
 }