[PATCH 20/32] btrfs: disk-io: only clear EXTENT_LOCK bit for extent_invalidatepage()

[Qu Wenruo <wqu@suse.com>]

In extent_invalidatepage() it will try to clear all possible bits since
it's calling clear_extent_bit() with delete == 1.
That would try to clear all existing bits.

This is currently fine, since for btree io tree, it only utilizes
EXTENT_LOCK bit.
But this could be a problem for later subpage support, which will
utilize extra io tree bit to represent extra info.

This patch will just convert that clear_extent_bit() to
unlock_extent_cached().

For current code since only EXTENT_LOCKED bit is utilized, this doesn't
change the behavior, but provides a much cleaner basis for incoming
subpage support.

Signed-off-by: Qu Wenruo <wqu@suse.com>
---
 fs/btrfs/extent_io.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index c7adcd99451a..b770ac039b96 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -4459,14 +4459,22 @@ int extent_invalidatepage(struct extent_io_tree *tree,
 	u64 end = start + PAGE_SIZE - 1;
 	size_t blocksize = page->mapping->host->i_sb->s_blocksize;
 
+	/* This function is only called for btree */
+	ASSERT(tree->owner == IO_TREE_BTREE_INODE_IO);
+
 	start += ALIGN(offset, blocksize);
 	if (start > end)
 		return 0;
 
 	lock_extent_bits(tree, start, end, &cached_state);
 	wait_on_page_writeback(page);
-	clear_extent_bit(tree, start, end, EXTENT_LOCKED | EXTENT_DELALLOC |
-			 EXTENT_DO_ACCOUNTING, 1, 1, &cached_state);
+
+	/*
+	 * Currently for btree io tree, only EXTENT_LOCKED is utilized,
+	 * so here we only need to unlock the extent range to free any
+	 * existing extent state.
+	 */
+	unlock_extent_cached(tree, start, end, &cached_state);
 	return 0;
 }
 
-- 
2.29.2