@@ -5671,6 +5671,7 @@ int btrfs_delalloc_reserve_metadata(struct inode *inode, u64 num_bytes)
bool delalloc_lock = true;
u64 to_free = 0;
unsigned dropped;
+ int loops = 0;
/* If we are a free space inode we need to not flush since we will be in
* the middle of a transaction commit. We also don't need the delalloc
@@ -5686,11 +5687,12 @@ int btrfs_delalloc_reserve_metadata(struct inode *inode, u64 num_bytes)
btrfs_transaction_in_commit(root->fs_info))
schedule_timeout(1);
+ num_bytes = ALIGN(num_bytes, root->sectorsize);
+
+again:
if (delalloc_lock)
mutex_lock(&BTRFS_I(inode)->delalloc_mutex);
- num_bytes = ALIGN(num_bytes, root->sectorsize);
-
spin_lock(&BTRFS_I(inode)->lock);
nr_extents = (unsigned)div64_u64(num_bytes +
BTRFS_MAX_EXTENT_SIZE - 1,
@@ -5811,6 +5813,23 @@ out_fail:
}
if (delalloc_lock)
mutex_unlock(&BTRFS_I(inode)->delalloc_mutex);
+ /*
+ * The number of metadata bytes is calculated by the difference
+ * between outstanding_extents and reserved_extents. Sometimes though
+ * reserve_metadata_bytes() fails to reserve the wanted metadata bytes,
+ * indeed it has already done some work to reclaim metadata space, hence
+ * both outstanding_extents and reserved_extents would have changed and
+ * the bytes we try to reserve would also has changed(may be smaller).
+ * So here we try to reserve again. This is much useful for online
+ * dedup, which will easily eat almost all meta space.
+ *
+ * XXX: Indeed here 3 is arbitrarily choosed, it's a good workaround for
+ * online dedup, later we should find a better method to avoid dedup
+ * enospc issue.
+ */
+ if (unlikely(ret == -ENOSPC && loops++ < 3))
+ goto again;
+
return ret;
}