[PATCH v5 02/18] btrfs: set UNMAPPED bit early in btrfs_clone_extent_buffer() for subpage support

[Qu Wenruo]

For the incoming subpage support, UNMAPPED extent buffer will have
different behavior in btrfs_release_extent_buffer().

This means we need to set UNMAPPED bit early before calling
btrfs_release_extent_buffer().

Currently there is only one caller which relies on
btrfs_release_extent_buffer() in its error path while set UNMAPPED bit
late:
- btrfs_clone_extent_buffer()

Make it subpage compatible by setting the UNMAPPED bit early, since
we're here, also move the UPTODATE bit early.

There is another caller, __alloc_dummy_extent_buffer(), setting UNAMPPED
bit late, but that function clean up the allocated page manually, thus
no need for any modification.

Signed-off-by: Qu Wenruo <w...@suse.com>
---
 fs/btrfs/extent_io.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 6cd81c6e8996..a56391839aca 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -5062,6 +5062,13 @@ struct extent_buffer *btrfs_clone_extent_buffer(const 
struct extent_buffer *src)
        if (new == NULL)
                return NULL;
 
+       /*
+        * Set UNMAPPED bfore calling btrfs_release_extent_buffer(), as
+        * btrfs_release_extent_buffer() have different behavior for
+        * UNMAPPED subpage extent buffer.
+        */
+       set_bit(EXTENT_BUFFER_UNMAPPED, &new->bflags);
+
        for (i = 0; i < num_pages; i++) {
                p = alloc_page(GFP_NOFS);
                if (!p) {
@@ -5074,9 +5081,7 @@ struct extent_buffer *btrfs_clone_extent_buffer(const 
struct extent_buffer *src)
                new->pages[i] = p;
                copy_page(page_address(p), page_address(src->pages[i]));
        }
-
        set_bit(EXTENT_BUFFER_UPTODATE, &new->bflags);
-       set_bit(EXTENT_BUFFER_UNMAPPED, &new->bflags);
 
        return new;
 }
-- 
2.30.0