btrfs: fix folio refcount in btrfs_do_encoded_write()

The conversion to folios switched __free_page() to __folio_put() in the
error path in btrfs_do_encoded_write().

However, this gets the page refcounting wrong. If we do hit that error
path (I reproduced by modifying btrfs_do_encoded_write to pretend to
always fail in a way that jumps to out_folios and running the fstests
case btrfs/281), then we always hit the following BUG freeing the folio:

  BUG: Bad page state in process btrfs  pfn:40ab0b
  page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x61be5 pfn:0x40ab0b
   flags: 0x5ffff0000000000(node=0|zone=2|lastcpupid=0x1ffff)
  raw: 05ffff0000000000 0000000000000000 dead000000000122 0000000000000000
  raw: 0000000000061be5 0000000000000000 00000001ffffffff 0000000000000000
  page dumped because: nonzero _refcount
  Call Trace:
  <TASK>
  dump_stack_lvl+0x3d/0xe0
  bad_page+0xea/0xf0
  free_unref_page+0x8e1/0x900
  ? __mem_cgroup_uncharge+0x69/0x90
  __folio_put+0xe6/0x190
  btrfs_do_encoded_write+0x445/0x780
  ? current_time+0x25/0xd0
  btrfs_do_write_iter+0x2cc/0x4b0
  btrfs_ioctl_encoded_write+0x2b6/0x340

It turns out __free_page() decreases the page reference count while
__folio_put() does not. Switch __folio_put() to folio_put() which
decreases the folio reference count first.

Fixes: 400b172b ("btrfs: compression: migrate compression/decompression paths to folios")
Tested-by: Ed Tomlinson <edtoml@gmail.com>
Reviewed-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Boris Burkov <boris@bur.io>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/inode.c

@@ -10382,7 +10382,7 @@ ssize_t btrfs_do_encoded_write(struct kiocb *iocb, struct iov_iter *from,
 out_folios:
 	for (i = 0; i < nr_folios; i++) {
 		if (folios[i])
-			__folio_put(folios[i]);
+			folio_put(folios[i]);
 	}
 	kvfree(folios);
 out: