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Btrfs: tree mod log sanity checks in join_transaction

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When a fresh transaction begins, the tree mod log must be clean. Users of
the tree modification log must ensure they never span across transaction
boundaries.

We reset the sequence to 0 in this safe situation to make absolutely sure
overflow can't happen.

Signed-off-by: Jan Schmidt <list.btrfs@jan-o-sch.net>
This commit is contained in:
Jan Schmidt 2012-05-20 15:43:53 +02:00
parent 19ae4e8133
commit 20b297d620
1 changed files with 18 additions and 0 deletions
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18
fs/btrfs/transaction.c
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@ -122,6 +122,24 @@ static noinline int join_transaction(struct btrfs_root *root, int nofail)
cur_trans->delayed_refs.flushing = 0;
cur_trans->delayed_refs.run_delayed_start = 0;
cur_trans->delayed_refs.seq = 1;
/*
* although the tree mod log is per file system and not per transaction,
* the log must never go across transaction boundaries.
*/
smp_mb();
if (!list_empty(&fs_info->tree_mod_seq_list)) {
printk(KERN_ERR "btrfs: tree_mod_seq_list not empty when "
"creating a fresh transaction\n");
WARN_ON(1);
}
if (!RB_EMPTY_ROOT(&fs_info->tree_mod_log)) {
printk(KERN_ERR "btrfs: tree_mod_log rb tree not empty when "
"creating a fresh transaction\n");
WARN_ON(1);
}
atomic_set(&fs_info->tree_mod_seq, 0);
init_waitqueue_head(&cur_trans->delayed_refs.seq_wait);
spin_lock_init(&cur_trans->commit_lock);
spin_lock_init(&cur_trans->delayed_refs.lock);