On Tue, 3 Nov 2009, Josef Bacik wrote:
> We use journal_info to tell if we're in a nested transaction to make sure we
> don't commit the transaction within a nested transaction. We use another
Might this also make btrfs_start_transaction() safe to call when another
transaction is already open? (i.e., let us choose between START and JOIN
to avoid wait_current_trans() if journal_info != NULL?)
If so, that would nicely solve the deadlocks with the alternate
transaction ioctl I'm putting together (and, if we drop the current ioctl,
make the existing open_ioctl_trans counter and associated checks go away).
I was looking at adding something to current->fs (struct fs_struct) to
flag if we're part of a user transaction, but if journal_info is already
being used that would be much cleaner.
sage
> method to see if there are any outstanding ioctl trans handles, so if we're
> starting one do not set current->journal_info, since it will screw with other
> filesystems. This patch also cleans up the starting stuff so there aren't any
> magic numbers.
>
> Signed-off-by: Josef Bacik <josef@xxxxxxxxxx>
> ---
> fs/btrfs/transaction.c | 19 +++++++++++++------
> 1 files changed, 13 insertions(+), 6 deletions(-)
>
> diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
> index bca82a4..c207e8c 100644
> --- a/fs/btrfs/transaction.c
> +++ b/fs/btrfs/transaction.c
> @@ -163,8 +163,14 @@ static void wait_current_trans(struct btrfs_root *root)
> }
> }
>
> +enum btrfs_trans_type {
> + TRANS_START,
> + TRANS_JOIN,
> + TRANS_USERSPACE,
> +};
> +
> static struct btrfs_trans_handle *start_transaction(struct btrfs_root *root,
> - int num_blocks, int wait)
> + int num_blocks, int type)
> {
> struct btrfs_trans_handle *h =
> kmem_cache_alloc(btrfs_trans_handle_cachep, GFP_NOFS);
> @@ -172,7 +178,8 @@ static struct btrfs_trans_handle *start_transaction(struct btrfs_root *root,
>
> mutex_lock(&root->fs_info->trans_mutex);
> if (!root->fs_info->log_root_recovering &&
> - ((wait == 1 && !root->fs_info->open_ioctl_trans) || wait == 2))
> + ((type == TRANS_START && !root->fs_info->open_ioctl_trans) ||
> + type == TRANS_USERSPACE))
> wait_current_trans(root);
> ret = join_transaction(root);
> BUG_ON(ret);
> @@ -186,7 +193,7 @@ static struct btrfs_trans_handle *start_transaction(struct btrfs_root *root,
> h->alloc_exclude_start = 0;
> h->delayed_ref_updates = 0;
>
> - if (!current->journal_info)
> + if (!current->journal_info && type != TRANS_USERSPACE)
> current->journal_info = h;
>
> root->fs_info->running_transaction->use_count++;
> @@ -198,18 +205,18 @@ static struct btrfs_trans_handle *start_transaction(struct btrfs_root *root,
> struct btrfs_trans_handle *btrfs_start_transaction(struct btrfs_root *root,
> int num_blocks)
> {
> - return start_transaction(root, num_blocks, 1);
> + return start_transaction(root, num_blocks, TRANS_START);
> }
> struct btrfs_trans_handle *btrfs_join_transaction(struct btrfs_root *root,
> int num_blocks)
> {
> - return start_transaction(root, num_blocks, 0);
> + return start_transaction(root, num_blocks, TRANS_JOIN);
> }
>
> struct btrfs_trans_handle *btrfs_start_ioctl_transaction(struct btrfs_root *r,
> int num_blocks)
> {
> - return start_transaction(r, num_blocks, 2);
> + return start_transaction(r, num_blocks, TRANS_USERSPACE);
> }
>
> /* wait for a transaction commit to be fully complete */
> --
> 1.5.4.3
>
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