btrfs: do regular iput instead of delayed iput during extent map shrinking

The extent map shrinker now runs in the system unbound workqueue and no
longer in kswapd context so it can directly do an iput() on inodes even
if that blocks or needs to acquire any lock (we aren't holding any locks
when requesting the delayed iput from the shrinker). So we don't need to
add a delayed iput, wake up the cleaner and delegate the iput() to the
cleaner, which also adds extra contention on the spinlock that protects
the delayed iputs list.

Reported-by: Ivan Shapovalov <[email protected]>
Tested-by: Ivan Shapovalov <[email protected]>
Link: https://lore.kernel.org/linux-btrfs/[email protected]/
CC: [email protected] # 6.12+
Reviewed-by: Johannes Thumshirn <[email protected]>
Reviewed-by: Qu Wenruo <[email protected]>
Signed-off-by: Filipe Manana <[email protected]>
Signed-off-by: David Sterba <[email protected]>

Author: fdmanana

fs/btrfs/extent_map.c

@@ -1256,7 +1256,7 @@ static long btrfs_scan_root(struct btrfs_root *root, struct btrfs_em_shrink_ctx
 
 		min_ino = btrfs_ino(inode) + 1;
 		fs_info->em_shrinker_last_ino = btrfs_ino(inode);
-		btrfs_add_delayed_iput(inode);
+		iput(&inode->vfs_inode);
 
 		if (ctx->scanned >= ctx->nr_to_scan || btrfs_fs_closing(fs_info))
 			break;