[PATCH, RFC 2/3] ext4: Add support for adding boolean toggls to ext4's sysfs directory

["Theodore Ts'o" <tytso@xxxxxxx>]

Signed-off-by: "Theodore Ts'o" <tytso@xxxxxxx>
---
 fs/ext4/super.c |   37 ++++++++++++++++++++++++++++++++++---
 1 files changed, 34 insertions(+), 3 deletions(-)

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 3d1a056..1d23b65 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -2213,6 +2213,7 @@ struct ext4_attr {
 	ssize_t (*store)(struct ext4_attr *, struct ext4_sb_info *, 
 			 const char *, size_t);
 	int offset;
+	unsigned int mask;
 };
 
 static int parse_strtoul(const char *buf,
@@ -2294,12 +2295,40 @@ static ssize_t sbi_ui_store(struct ext4_attr *a,
 	return count;
 }
 
-#define EXT4_ATTR_OFFSET(_name,_mode,_show,_store,_elname) \
+static ssize_t sbi_bool_show(struct ext4_attr *a,
+			     struct ext4_sb_info *sbi, char *buf)
+{
+	unsigned int *ui = (unsigned int *) (((char *) sbi) + a->offset);
+
+	return snprintf(buf, PAGE_SIZE, "%d\n",
+			((*ui & a->mask) == 0) ? 0 : 1);
+}
+
+static ssize_t sbi_bool_store(struct ext4_attr *a,
+			      struct ext4_sb_info *sbi,
+			      const char *buf, size_t count)
+{
+	unsigned int *ui = (unsigned int *) (((char *) sbi) + a->offset);
+	unsigned long t;
+
+	if (parse_strtoul(buf, 0xffffffff, &t))
+		return -EINVAL;
+	if (t)
+		*ui |= a->mask;
+	else
+		*ui &= ~a->mask;
+
+	return count;
+}
+
+
+#define EXT4_ATTR_OFFSET(_name,_mode,_show,_store,_elname,_mask)\
 static struct ext4_attr ext4_attr_##_name = {			\
 	.attr = {.name = __stringify(_name), .mode = _mode },	\
 	.show	= _show,					\
 	.store	= _store,					\
 	.offset = offsetof(struct ext4_sb_info, _elname),	\
+	.mask   = (_mask),                                      	\
 }
 #define EXT4_ATTR(name, mode, show, store) \
 static struct ext4_attr ext4_attr_##name = __ATTR(name, mode, show, store)
@@ -2307,14 +2336,16 @@ static struct ext4_attr ext4_attr_##name = __ATTR(name, mode, show, store)
 #define EXT4_RO_ATTR(name) EXT4_ATTR(name, 0444, name##_show, NULL)
 #define EXT4_RW_ATTR(name) EXT4_ATTR(name, 0644, name##_show, name##_store)
 #define EXT4_RW_ATTR_SBI_UI(name, elname)	\
-	EXT4_ATTR_OFFSET(name, 0644, sbi_ui_show, sbi_ui_store, elname)
+	EXT4_ATTR_OFFSET(name, 0644, sbi_ui_show, sbi_ui_store, elname, 0)
+#define EXT4_RW_ATTR_SBI_BOOL(name, elname, mask)			\
+EXT4_ATTR_OFFSET(name, 0644, sbi_bool_show, sbi_bool_store, elname, mask)
 #define ATTR_LIST(name) &ext4_attr_##name.attr
 
 EXT4_RO_ATTR(delayed_allocation_blocks);
 EXT4_RO_ATTR(session_write_kbytes);
 EXT4_RO_ATTR(lifetime_write_kbytes);
 EXT4_ATTR_OFFSET(inode_readahead_blks, 0644, sbi_ui_show,
-		 inode_readahead_blks_store, s_inode_readahead_blks);
+		 inode_readahead_blks_store, s_inode_readahead_blks, 0);
 EXT4_RW_ATTR_SBI_UI(inode_goal, s_inode_goal);
 EXT4_RW_ATTR_SBI_UI(mb_stats, s_mb_stats);
 EXT4_RW_ATTR_SBI_UI(mb_max_to_scan, s_mb_max_to_scan);
-- 
1.6.6.1.1.g974db.dirty

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