Re: WARNING: at fs/btrfs/free-space-cache.c:921 __btrfs_write_out_cache+0x6b9/0x9a0 [btrfs]()

[Josef Bacik <jbacik@fusionio.com>]

On Tue, Apr 30, 2013 at 08:33:38AM -0600, Alexander Skwar wrote:
> Hello Josef
> 
> On Tue, Apr 30, 2013 at 3:58 PM, Josef Bacik <jbacik@fusionio.com> wrote:
> 
> > So we deal with this case fine, but it really shouldn't be happening, it only
> > happens if your block groups are way too large, which again shouldn't be
> > happening.  Can you run fsck on this device and see if it complains?  Thanks,
> 
> 
> a@ewzw032:~$ sudo btrfsck /dev/system/Data
> checking extents
> checking fs roots
> checking root refs
> found 115308904448 bytes used err is 0
> total csum bytes: 112056692
> total tree bytes: 521891840
> total fs tree bytes: 353947648
> btree space waste bytes: 122297974
> file data blocks allocated: 114787012608
>  referenced 114787000320
> Btrfs v0.20-rc1
> 

Can you run this patch and capture the output when you get the warning?  You
should see some mesages before the -- [ cut here ] -- part, make sure to capture
those.  Thanks,

Josef

diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
index ecca6c7..2e8e098 100644
--- a/fs/btrfs/free-space-cache.c
+++ b/fs/btrfs/free-space-cache.c
@@ -921,6 +921,10 @@ static int __btrfs_write_out_cache(struct btrfs_root *root, struct inode *inode,
 	/* Make sure we can fit our crcs into the first page */
 	if (io_ctl.check_crcs &&
 	    (io_ctl.num_pages * sizeof(u32)) >= PAGE_CACHE_SIZE) {
+		printk(KERN_ERR "num_pages is %d, blockgroup? %s\n",
+		       io_ctl.num_pages, block_group ? "yes" : "no");
+		if (block_group)
+			printk(KERN_ERR "block group offset=%Lu, size=%Lu\n", block_group->key.objectid, block_group->key.offset);
 		WARN_ON(1);
 		goto out_nospc;
 	}