Btrfs: limit the global reserve to 512mb

commit fdf30d1c1b386e1b73116cc7e0fb14e962b763b0 upstream.

A user reported a problem where he was getting early ENOSPC with hundreds of
gigs of free data space and 6 gigs of free metadata space.  This is because the
global block reserve was taking up the entire free metadata space.  This is
ridiculous, we have infrastructure in place to throttle if we start using too
much of the global reserve, so instead of letting it get this huge just limit it
to 512mb so that users can still get work done.  This allowed the user to
complete his rsync without issues.  Thanks

Reported-and-tested-by: Stefan Priebe <s.priebe@profihost.ag>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 49fd7b66d57b272c7aeaea7db4b1bbd0985f8aa2..ee6abb8fa71ca55ea7878b6286935181c81422b0 100644 (file)
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -4217,7 +4217,7 @@ static void update_global_block_rsv(struct btrfs_fs_info *fs_info)
        spin_lock(&sinfo->lock);
        spin_lock(&block_rsv->lock);
 
-       block_rsv->size = num_bytes;
+       block_rsv->size = min_t(u64, num_bytes, 512 * 1024 * 1024);
 
        num_bytes = sinfo->bytes_used + sinfo->bytes_pinned +
                    sinfo->bytes_reserved + sinfo->bytes_readonly +