fs: add a write stream field to the inode

Prepare for supporting per-inode write streams.
Part of the existing 32-bit hole is used for the new field.

Signed-off-by: Kanchan Joshi <[email protected]>

Author: Kanchan Joshi

fs/inode.c

@@ -250,6 +250,7 @@ int inode_init_always_gfp(struct super_block *sb, struct inode *inode, gfp_t gfp
 	atomic_set(&inode->i_writecount, 0);
 	inode->i_size = 0;
 	inode->i_write_hint = WRITE_LIFE_NOT_SET;
+	inode->i_write_stream = 0;
 	inode->i_blocks = 0;
 	inode->i_bytes = 0;
 	inode->i_generation = 0;

include/linux/fs.h

@@ -725,7 +725,8 @@ struct inode {
 
 	/* Misc */
 	u32			i_state;
-	/* 32-bit hole */
+	u8			i_write_stream;
+	/* 24-bit hole */
 	struct rw_semaphore	i_rwsem;
 
 	unsigned long		dirtied_when;	/* jiffies of first dirtying */