btrfs: consolidate auto defrag kick off policies

As of now writes smaller than 64k for non compressed extents and 16k
for compressed extents inside eof are considered as candidate
for auto defrag, put them together at a place.
Signed-off-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/inode.c

@@ -388,6 +388,15 @@ static inline int inode_need_compress(struct inode *inode)
 	return 0;
 }
 
+static inline void inode_should_defrag(struct inode *inode,
+		u64 start, u64 end, u64 num_bytes, u64 small_write)
+{
+	/* If this is a small write inside eof, kick off a defrag */
+	if (num_bytes < small_write &&
+	    (start > 0 || end + 1 < BTRFS_I(inode)->disk_i_size))
+		btrfs_add_inode_defrag(NULL, inode);
+}
+
 /*
  * we create compressed extents in two phases.  The first
  * phase compresses a range of pages that have already been
@@ -430,10 +439,7 @@ static noinline void compress_file_range(struct inode *inode,
 	int compress_type = fs_info->compress_type;
 	int redirty = 0;
 
-	/* if this is a small write inside eof, kick off a defrag */
-	if ((end - start + 1) < SZ_16K &&
-	    (start > 0 || end + 1 < BTRFS_I(inode)->disk_i_size))
-		btrfs_add_inode_defrag(NULL, inode);
+	inode_should_defrag(inode, start, end, end - start + 1, SZ_16K);
 
 	actual_end = min_t(u64, isize, end + 1);
 again:
@@ -965,10 +971,7 @@ static noinline int cow_file_range(struct inode *inode,
 	num_bytes = max(blocksize,  num_bytes);
 	disk_num_bytes = num_bytes;
 
-	/* if this is a small write inside eof, kick off defrag */
-	if (num_bytes < SZ_64K &&
-	    (start > 0 || end + 1 < BTRFS_I(inode)->disk_i_size))
-		btrfs_add_inode_defrag(NULL, inode);
+	inode_should_defrag(inode, start, end, num_bytes, SZ_64K);
 
 	if (start == 0) {
 		/* lets try to make an inline extent */