Btrfs: use the global block reserve if we cannot reserve space
We call use_block_rsv right before we make an allocation in order to make sure
we have enough space. Now normally people have called btrfs_start_transaction()
with the appropriate amount of space that we need, so we just use some of that
pre-reserved space and move along happily. The problem is where people use
btrfs_join_transaction(), which doesn't actually reserve any space. So we try
and reserve space here, but we cannot flush delalloc, so this forces us to
return -ENOSPC when in reality we have plenty of space. The most common symptom
is seeing a bunch of "couldn't dirty inode" messages in syslog. With
xfstests 224 we end up falling back to start_transaction and then doing all the
flush delalloc stuff which causes to hang for a very long time.
So instead steal from the global reserve, which is what this is meant for
anyway. With this patch and the other 2 I have sent xfstests 224 now passes
successfully. Thanks,
Signed-off-by: Josef Bacik <josef@redhat.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 7af618d..ff6bbfd 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -5646,6 +5646,7 @@
struct btrfs_root *root, u32 blocksize)
{
struct btrfs_block_rsv *block_rsv;
+ struct btrfs_block_rsv *global_rsv = &root->fs_info->global_block_rsv;
int ret;
block_rsv = get_block_rsv(trans, root);
@@ -5653,14 +5654,39 @@
if (block_rsv->size == 0) {
ret = reserve_metadata_bytes(trans, root, block_rsv,
blocksize, 0);
- if (ret)
+ /*
+ * If we couldn't reserve metadata bytes try and use some from
+ * the global reserve.
+ */
+ if (ret && block_rsv != global_rsv) {
+ ret = block_rsv_use_bytes(global_rsv, blocksize);
+ if (!ret)
+ return global_rsv;
return ERR_PTR(ret);
+ } else if (ret) {
+ return ERR_PTR(ret);
+ }
return block_rsv;
}
ret = block_rsv_use_bytes(block_rsv, blocksize);
if (!ret)
return block_rsv;
+ if (ret) {
+ WARN_ON(1);
+ ret = reserve_metadata_bytes(trans, root, block_rsv, blocksize,
+ 0);
+ if (!ret) {
+ spin_lock(&block_rsv->lock);
+ block_rsv->size += blocksize;
+ spin_unlock(&block_rsv->lock);
+ return block_rsv;
+ } else if (ret && block_rsv != global_rsv) {
+ ret = block_rsv_use_bytes(global_rsv, blocksize);
+ if (!ret)
+ return global_rsv;
+ }
+ }
return ERR_PTR(-ENOSPC);
}