Btrfs: if we've already started a trans handle, use that one

We currently track trans handles in current->journal_info, but we don't actually
use it.  This patch fixes it.  This will cover the case where we have multiple
people starting transactions down the call chain.  This keeps us from having to
allocate a new handle and all of that, we just increase the use count of the
current handle, save the old block_rsv, and return.  I tested this with xfstests
and it worked out fine.  Thanks,

Signed-off-by: Josef Bacik <josef@redhat.com>

diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index 70bfb26df967f93af0fa044abe89ba97344c2d60..46f40564c16885f9a01f8ef08496d82ed42b14a7 100644 (file)
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -184,6 +184,15 @@ static struct btrfs_trans_handle *start_transaction(struct btrfs_root *root,
 
        if (root->fs_info->fs_state & BTRFS_SUPER_FLAG_ERROR)
                return ERR_PTR(-EROFS);
+
+       if (current->journal_info) {
+               WARN_ON(type != TRANS_JOIN && type != TRANS_JOIN_NOLOCK);
+               h = current->journal_info;
+               h->use_count++;
+               h->orig_rsv = h->block_rsv;
+               h->block_rsv = NULL;
+               goto got_it;
+       }
 again:
        h = kmem_cache_alloc(btrfs_trans_handle_cachep, GFP_NOFS);
        if (!h)
@@ -213,7 +222,9 @@ again:
        h->block_group = 0;
        h->bytes_reserved = 0;
        h->delayed_ref_updates = 0;
+       h->use_count = 1;
        h->block_rsv = NULL;
+       h->orig_rsv = NULL;
 
        smp_mb();
        if (cur_trans->blocked && may_wait_transaction(root, type)) {
@@ -241,6 +252,7 @@ again:
                }
        }
 
+got_it:
        if (type != TRANS_JOIN_NOLOCK)
                mutex_lock(&root->fs_info->trans_mutex);
        record_root_in_trans(h, root);
@@ -428,6 +440,11 @@ static int __btrfs_end_transaction(struct btrfs_trans_handle *trans,
        struct btrfs_fs_info *info = root->fs_info;
        int count = 0;
 
+       if (--trans->use_count) {
+               trans->block_rsv = trans->orig_rsv;
+               return 0;
+       }
+
        while (count < 4) {
                unsigned long cur = trans->delayed_ref_updates;
                trans->delayed_ref_updates = 0;

diff --git a/fs/btrfs/transaction.h b/fs/btrfs/transaction.h
index 1f573f09dba240a3292b056a62887402e92568f1..154314f80f8de87b1e5ee1d06459313d83a04e6e 100644 (file)
--- a/fs/btrfs/transaction.h
+++ b/fs/btrfs/transaction.h
@@ -47,11 +47,13 @@ struct btrfs_trans_handle {
        u64 transid;
        u64 block_group;
        u64 bytes_reserved;
+       unsigned long use_count;
        unsigned long blocks_reserved;
        unsigned long blocks_used;
        unsigned long delayed_ref_updates;
        struct btrfs_transaction *transaction;
        struct btrfs_block_rsv *block_rsv;
+       struct btrfs_block_rsv *orig_rsv;
 };
 
 struct btrfs_pending_snapshot {