Josef Bacik
2011-Apr-11 21:26 UTC
[PATCH] Btrfs: only drop the trans_mutex in join_transaction if we have to
I noticed we are dropping the trans_mutex and then immediately re-acquiring it
in the common case in join_transaction. Instead of doing that, just drop it if
we have to (like we have to commit or end the transaction or something) and
otherwise just keep a hold of it. Thanks,
Signed-off-by: Josef Bacik <josef@redhat.com>
---
fs/btrfs/transaction.c | 20 +++++++++++++-------
1 files changed, 13 insertions(+), 7 deletions(-)
diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index c571734..cde38f9 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -181,6 +181,7 @@ static struct btrfs_trans_handle *start_transaction(struct
btrfs_root *root,
struct btrfs_transaction *cur_trans;
int retries = 0;
int ret;
+ bool lock = (type != TRANS_JOIN_NOLOCK);
if (root->fs_info->fs_state & BTRFS_SUPER_FLAG_ERROR)
return ERR_PTR(-EROFS);
@@ -189,7 +190,7 @@ again:
if (!h)
return ERR_PTR(-ENOMEM);
- if (type != TRANS_JOIN_NOLOCK)
+ if (lock)
mutex_lock(&root->fs_info->trans_mutex);
if (may_wait_transaction(root, type))
wait_current_trans(root);
@@ -197,15 +198,13 @@ again:
ret = join_transaction(root);
if (ret < 0) {
kmem_cache_free(btrfs_trans_handle_cachep, h);
- if (type != TRANS_JOIN_NOLOCK)
+ if (lock)
mutex_unlock(&root->fs_info->trans_mutex);
return ERR_PTR(ret);
}
cur_trans = root->fs_info->running_transaction;
atomic_inc(&cur_trans->use_count);
- if (type != TRANS_JOIN_NOLOCK)
- mutex_unlock(&root->fs_info->trans_mutex);
h->transid = cur_trans->transid;
h->transaction = cur_trans;
@@ -217,6 +216,11 @@ again:
smp_mb();
if (cur_trans->blocked && may_wait_transaction(root, type)) {
+ /*
+ * No need to test for lock since may_wait_transaction will only
+ * return 1 if we had to take the trans_mutex anyway.
+ */
+ mutex_unlock(&root->fs_info->trans_mutex);
btrfs_commit_transaction(h, root);
goto again;
}
@@ -225,6 +229,8 @@ again:
ret = btrfs_trans_reserve_metadata(h, root, num_items);
if (ret == -EAGAIN && !retries) {
retries++;
+ if (lock)
+ mutex_unlock(&root->fs_info->trans_mutex);
btrfs_commit_transaction(h, root);
goto again;
} else if (ret == -EAGAIN) {
@@ -236,15 +242,15 @@ again:
}
if (ret < 0) {
+ if (lock)
+ mutex_unlock(&root->fs_info->trans_mutex);
btrfs_end_transaction(h, root);
return ERR_PTR(ret);
}
}
- if (type != TRANS_JOIN_NOLOCK)
- mutex_lock(&root->fs_info->trans_mutex);
record_root_in_trans(h, root);
- if (type != TRANS_JOIN_NOLOCK)
+ if (lock)
mutex_unlock(&root->fs_info->trans_mutex);
if (!current->journal_info && type != TRANS_USERSPACE)
--
1.7.2.3
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