btrfs: ignore unfragmented file checks in defrag when compression enabled - rebased

Rebased on btrfs-next and retested.

Inform should_defrag_range if BTRFS_DEFRAG_RANGE_COMPRESS is set. If so, skip
checks for adjacent extents and extent size when deciding whether to defrag,
as these can prevent an uncompressed and unfragmented file from being
compressed as requested.
Signed-off-by: Andrew Mahone <andrew.mahone@gmail.com>

fs/btrfs/ioctl.c

@@ -832,7 +832,8 @@ static bool defrag_check_next_extent(struct inode *inode, struct extent_map *em)
 }
 
 static int should_defrag_range(struct inode *inode, u64 start, int thresh,
-			       u64 *last_len, u64 *skip, u64 *defrag_end)
+			       u64 *last_len, u64 *skip, u64 *defrag_end,
+			       int compress)
 {
 	struct extent_map *em;
 	int ret = 1;
@@ -863,7 +864,7 @@ static int should_defrag_range(struct inode *inode, u64 start, int thresh,
 	 * we hit a real extent, if it is big or the next extent is not a
 	 * real extent, don't bother defragging it
 	 */
-	if ((*last_len == 0 || *last_len >= thresh) &&
+	if (!compress && (*last_len == 0 || *last_len >= thresh) &&
 	    (em->len >= thresh || !next_mergeable))
 		ret = 0;
 out:
@@ -1145,7 +1146,8 @@ int btrfs_defrag_file(struct inode *inode, struct file *file,
 
 		if (!should_defrag_range(inode, (u64)i << PAGE_CACHE_SHIFT,
 					 extent_thresh, &last_len, &skip,
-					 &defrag_end)) {
+					 &defrag_end, range->flags &
+					 BTRFS_DEFRAG_RANGE_COMPRESS)) {
 			unsigned long next;
 			/*
 			 * the should_defrag function tells us how much to skip