From d4edf39bd5db443151efc993dac67ec9d6b5b8c1 Mon Sep 17 00:00:00 2001 From: Miao Xie Date: Wed, 20 Feb 2013 09:17:06 +0000 Subject: [PATCH] Btrfs: fix uncompleted transaction In some cases, we need commit the current transaction, but don't want to start a new one if there is no running transaction, so we introduce the function - btrfs_attach_transaction(), which can catch the current transaction, and return -ENOENT if there is no running transaction. But no running transaction doesn't mean the current transction completely, because we removed the running transaction before it completes. In some cases, it doesn't matter. But in some special cases, such as freeze fs, we hope the transaction is fully on disk, it will introduce some bugs, for example, we may feeze the fs and dump the data in the disk, if the transction doesn't complete, we would dump inconsistent data. So we need fix the above problem for those cases. We fixes this problem by introducing a function: btrfs_attach_transaction_barrier() if we hope all the transaction is fully on the disk, even they are not running, we can use this function. Signed-off-by: Miao Xie Signed-off-by: Josef Bacik --- fs/btrfs/ioctl.c | 2 +- fs/btrfs/super.c | 4 ++-- fs/btrfs/transaction.c | 32 ++++++++++++++++++++++++++++++++ fs/btrfs/transaction.h | 2 ++ 4 files changed, 37 insertions(+), 3 deletions(-) diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c index 0f68729f261e..e0893036da08 100644 --- a/fs/btrfs/ioctl.c +++ b/fs/btrfs/ioctl.c @@ -3114,7 +3114,7 @@ static noinline long btrfs_ioctl_start_sync(struct btrfs_root *root, u64 transid; int ret; - trans = btrfs_attach_transaction(root); + trans = btrfs_attach_transaction_barrier(root); if (IS_ERR(trans)) { if (PTR_ERR(trans) != -ENOENT) return PTR_ERR(trans); diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c index e0ea1278377a..db1ba9a2ed64 100644 --- a/fs/btrfs/super.c +++ b/fs/btrfs/super.c @@ -878,7 +878,7 @@ int btrfs_sync_fs(struct super_block *sb, int wait) btrfs_wait_ordered_extents(root, 0); - trans = btrfs_attach_transaction(root); + trans = btrfs_attach_transaction_barrier(root); if (IS_ERR(trans)) { /* no transaction, don't bother */ if (PTR_ERR(trans) == -ENOENT) @@ -1563,7 +1563,7 @@ static int btrfs_freeze(struct super_block *sb) struct btrfs_trans_handle *trans; struct btrfs_root *root = btrfs_sb(sb)->tree_root; - trans = btrfs_attach_transaction(root); + trans = btrfs_attach_transaction_barrier(root); if (IS_ERR(trans)) { /* no transaction, don't bother */ if (PTR_ERR(trans) == -ENOENT) diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c index 5767ea1c0150..c1ce664c0c39 100644 --- a/fs/btrfs/transaction.c +++ b/fs/btrfs/transaction.c @@ -469,11 +469,43 @@ struct btrfs_trans_handle *btrfs_start_ioctl_transaction(struct btrfs_root *root return start_transaction(root, 0, TRANS_USERSPACE, 0); } +/* + * btrfs_attach_transaction() - catch the running transaction + * + * It is used when we want to commit the current the transaction, but + * don't want to start a new one. + * + * Note: If this function return -ENOENT, it just means there is no + * running transaction. But it is possible that the inactive transaction + * is still in the memory, not fully on disk. If you hope there is no + * inactive transaction in the fs when -ENOENT is returned, you should + * invoke + * btrfs_attach_transaction_barrier() + */ struct btrfs_trans_handle *btrfs_attach_transaction(struct btrfs_root *root) { return start_transaction(root, 0, TRANS_ATTACH, 0); } +/* + * btrfs_attach_transaction() - catch the running transaction + * + * It is similar to the above function, the differentia is this one + * will wait for all the inactive transactions until they fully + * complete. + */ +struct btrfs_trans_handle * +btrfs_attach_transaction_barrier(struct btrfs_root *root) +{ + struct btrfs_trans_handle *trans; + + trans = start_transaction(root, 0, TRANS_ATTACH, 0); + if (IS_ERR(trans) && PTR_ERR(trans) == -ENOENT) + btrfs_wait_for_commit(root, 0); + + return trans; +} + /* wait for a transaction commit to be fully complete */ static noinline void wait_for_commit(struct btrfs_root *root, struct btrfs_transaction *commit) diff --git a/fs/btrfs/transaction.h b/fs/btrfs/transaction.h index 3f772fd0191a..5afd7b1dceac 100644 --- a/fs/btrfs/transaction.h +++ b/fs/btrfs/transaction.h @@ -112,6 +112,8 @@ struct btrfs_trans_handle *btrfs_start_transaction_lflush( struct btrfs_trans_handle *btrfs_join_transaction(struct btrfs_root *root); struct btrfs_trans_handle *btrfs_join_transaction_nolock(struct btrfs_root *root); struct btrfs_trans_handle *btrfs_attach_transaction(struct btrfs_root *root); +struct btrfs_trans_handle *btrfs_attach_transaction_barrier( + struct btrfs_root *root); struct btrfs_trans_handle *btrfs_start_ioctl_transaction(struct btrfs_root *root); int btrfs_wait_for_commit(struct btrfs_root *root, u64 transid); int btrfs_write_and_wait_transaction(struct btrfs_trans_handle *trans,