f2fs: fix to check inline_xattr_size boundary correctly

We use below condition to check inline_xattr_size boundary:

	if (!F2FS_OPTION(sbi).inline_xattr_size ||
		F2FS_OPTION(sbi).inline_xattr_size >=
				DEF_ADDRS_PER_INODE -
				F2FS_TOTAL_EXTRA_ATTR_SIZE -
				DEF_INLINE_RESERVED_SIZE -
				DEF_MIN_INLINE_SIZE)

There is there problems in that check:
- we should allow inline_xattr_size equaling to min size of inline
{data,dentry} area.
- F2FS_TOTAL_EXTRA_ATTR_SIZE and inline_xattr_size are based on
different size unit, previous one is 4 bytes, latter one is 1 bytes.
- DEF_MIN_INLINE_SIZE only indicate min size of inline data area,
however, we need to consider min size of inline dentry area as well,
minimal inline dentry should at least contain two entries: '.' and
'..', so that min inline_dentry size is 40 bytes.

.bitmap		1 * 1 = 1
.reserved	1 * 1 = 1
.dentry		11 * 2 = 22
.filename	8 * 2 = 16
total		40
Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/f2fs.h

@@ -459,7 +459,6 @@ struct f2fs_flush_device {
 
 /* for inline stuff */
 #define DEF_INLINE_RESERVED_SIZE	1
-#define DEF_MIN_INLINE_SIZE		1
 static inline int get_extra_isize(struct inode *inode);
 static inline int get_inline_xattr_addrs(struct inode *inode);
 #define MAX_INLINE_DATA(inode)	(sizeof(__le32) *			\

fs/f2fs/super.c

@@ -834,12 +834,13 @@ static int parse_options(struct super_block *sb, char *options)
 					"set with inline_xattr option");
 			return -EINVAL;
 		}
-		if (!F2FS_OPTION(sbi).inline_xattr_size ||
-			F2FS_OPTION(sbi).inline_xattr_size >=
-					DEF_ADDRS_PER_INODE -
-					F2FS_TOTAL_EXTRA_ATTR_SIZE -
-					DEF_INLINE_RESERVED_SIZE -
-					DEF_MIN_INLINE_SIZE) {
+		if (F2FS_OPTION(sbi).inline_xattr_size <
+			sizeof(struct f2fs_xattr_header) / sizeof(__le32) ||
+			F2FS_OPTION(sbi).inline_xattr_size >
+			DEF_ADDRS_PER_INODE -
+			F2FS_TOTAL_EXTRA_ATTR_SIZE / sizeof(__le32) -
+			DEF_INLINE_RESERVED_SIZE -
+			MIN_INLINE_DENTRY_SIZE / sizeof(__le32)) {
 			f2fs_msg(sb, KERN_ERR,
 					"inline xattr size is out of range");
 			return -EINVAL;

include/linux/f2fs_fs.h

@@ -490,12 +490,12 @@ typedef __le32	f2fs_hash_t;
 
 /*
  * space utilization of regular dentry and inline dentry (w/o extra reservation)
- *		regular dentry			inline dentry
- * bitmap	1 * 27 = 27			1 * 23 = 23
- * reserved	1 * 3 = 3			1 * 7 = 7
- * dentry	11 * 214 = 2354			11 * 182 = 2002
- * filename	8 * 214 = 1712			8 * 182 = 1456
- * total	4096				3488
+ *		regular dentry		inline dentry (def)	inline dentry (min)
+ * bitmap	1 * 27 = 27		1 * 23 = 23		1 * 1 = 1
+ * reserved	1 * 3 = 3		1 * 7 = 7		1 * 1 = 1
+ * dentry	11 * 214 = 2354		11 * 182 = 2002		11 * 2 = 22
+ * filename	8 * 214 = 1712		8 * 182 = 1456		8 * 2 = 16
+ * total	4096			3488			40
  *
  * Note: there are more reserved space in inline dentry than in regular
  * dentry, when converting inline dentry we should handle this carefully.
@@ -507,6 +507,7 @@ typedef __le32	f2fs_hash_t;
 #define SIZE_OF_RESERVED	(PAGE_SIZE - ((SIZE_OF_DIR_ENTRY + \
 				F2FS_SLOT_LEN) * \
 				NR_DENTRY_IN_BLOCK + SIZE_OF_DENTRY_BITMAP))
+#define MIN_INLINE_DENTRY_SIZE		40	/* just include '.' and '..' entries */
 
 /* One directory entry slot representing F2FS_SLOT_LEN-sized file name */
 struct f2fs_dir_entry {