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author | Chris Mason <chris.mason@oracle.com> | 2011-11-06 03:26:19 -0500 |
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committer | Chris Mason <chris.mason@oracle.com> | 2011-11-06 03:26:19 -0500 |
commit | d43317dcd074818d4bd12ddd4184a29aff98907b (patch) | |
tree | 233033cf8c7f3cb38dc549d2a1be7f0fc9ecfd80 | |
parent | 56d2a48f81a1bde827c625b90221fade72fe9c61 (diff) | |
download | linux-3.10-d43317dcd074818d4bd12ddd4184a29aff98907b.tar.gz linux-3.10-d43317dcd074818d4bd12ddd4184a29aff98907b.tar.bz2 linux-3.10-d43317dcd074818d4bd12ddd4184a29aff98907b.zip |
Btrfs: fix race during transaction joins
While we're allocating ram for a new transaction, we drop our spinlock.
When we get the lock back, we do check to see if a transaction started
while we slept, but we don't check to make sure it isn't blocked
because a commit has already started.
Signed-off-by: Chris Mason <chris.mason@oracle.com>
-rw-r--r-- | fs/btrfs/transaction.c | 13 |
1 files changed, 8 insertions, 5 deletions
diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c index 29f782cc2cc..960835eaf4d 100644 --- a/fs/btrfs/transaction.c +++ b/fs/btrfs/transaction.c @@ -55,6 +55,7 @@ static noinline int join_transaction(struct btrfs_root *root, int nofail) struct btrfs_transaction *cur_trans; spin_lock(&root->fs_info->trans_lock); +loop: if (root->fs_info->trans_no_join) { if (!nofail) { spin_unlock(&root->fs_info->trans_lock); @@ -75,16 +76,18 @@ static noinline int join_transaction(struct btrfs_root *root, int nofail) cur_trans = kmem_cache_alloc(btrfs_transaction_cachep, GFP_NOFS); if (!cur_trans) return -ENOMEM; + spin_lock(&root->fs_info->trans_lock); if (root->fs_info->running_transaction) { + /* + * someone started a transaction after we unlocked. Make sure + * to redo the trans_no_join checks above + */ kmem_cache_free(btrfs_transaction_cachep, cur_trans); cur_trans = root->fs_info->running_transaction; - atomic_inc(&cur_trans->use_count); - atomic_inc(&cur_trans->num_writers); - cur_trans->num_joined++; - spin_unlock(&root->fs_info->trans_lock); - return 0; + goto loop; } + atomic_set(&cur_trans->num_writers, 1); cur_trans->num_joined = 0; init_waitqueue_head(&cur_trans->writer_wait); |