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authorSage Weil <sage@newdream.net>2008-08-04 10:41:27 -0400
committerChris Mason <chris.mason@oracle.com>2008-09-25 11:04:06 -0400
commit9ca9ee09c176a814189063c8b88f75c8f8e4ad19 (patch)
tree3092ed3f5dd472e66a61da9306dfa6839604c42c /fs/btrfs/transaction.c
parent3117a77370b6cb902191568e4e647cdcba083d0a (diff)
downloadop-kernel-dev-9ca9ee09c176a814189063c8b88f75c8f8e4ad19.zip
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Btrfs: fix ioctl-initiated transactions vs wait_current_trans()
Commit 597:466b27332893 (btrfs_start_transaction: wait for commits in progress) breaks the transaction start/stop ioctls by making btrfs_start_transaction conditionally wait for the next transaction to start. If an application artificially is holding a transaction open, things deadlock. This workaround maintains a count of open ioctl-initiated transactions in fs_info, and avoids wait_current_trans() if any are currently open (in start_transaction() and btrfs_throttle()). The start transaction ioctl uses a new btrfs_start_ioctl_transaction() that _does_ call wait_current_trans(), effectively pushing the join/wait decision to the outer ioctl-initiated transaction. This more or less neuters btrfs_throttle() when ioctl-initiated transactions are in use, but that seems like a pretty fundamental consequence of wrapping lots of write()'s in a transaction. Btrfs has no way to tell if the application considers a given operation as part of it's transaction. Obviously, if the transaction start/stop ioctls aren't being used, there is no effect on current behavior. Signed-off-by: Sage Weil <sage@newdream.net> --- ctree.h | 1 + ioctl.c | 12 +++++++++++- transaction.c | 18 +++++++++++++----- transaction.h | 2 ++ 4 files changed, 27 insertions(+), 6 deletions(-) Signed-off-by: Chris Mason <chris.mason@oracle.com>
Diffstat (limited to 'fs/btrfs/transaction.c')
-rw-r--r--fs/btrfs/transaction.c18
1 files changed, 13 insertions, 5 deletions
diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index cf73342..a2c821e 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -152,14 +152,14 @@ static void wait_current_trans(struct btrfs_root *root)
}
struct btrfs_trans_handle *start_transaction(struct btrfs_root *root,
- int num_blocks, int join)
+ int num_blocks, int wait)
{
struct btrfs_trans_handle *h =
kmem_cache_alloc(btrfs_trans_handle_cachep, GFP_NOFS);
int ret;
mutex_lock(&root->fs_info->trans_mutex);
- if (!join)
+ if ((wait == 1 && !root->fs_info->open_ioctl_trans) || wait == 2)
wait_current_trans(root);
ret = join_transaction(root);
BUG_ON(ret);
@@ -180,14 +180,21 @@ 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, 0);
+ return start_transaction(root, num_blocks, 1);
}
struct btrfs_trans_handle *btrfs_join_transaction(struct btrfs_root *root,
int num_blocks)
{
- return start_transaction(root, num_blocks, 1);
+ return start_transaction(root, num_blocks, 0);
}
+struct btrfs_trans_handle *btrfs_start_ioctl_transaction(struct btrfs_root *r,
+ int num_blocks)
+{
+ return start_transaction(r, num_blocks, 2);
+}
+
+
static noinline int wait_for_commit(struct btrfs_root *root,
struct btrfs_transaction *commit)
{
@@ -247,7 +254,8 @@ harder:
void btrfs_throttle(struct btrfs_root *root)
{
mutex_lock(&root->fs_info->trans_mutex);
- wait_current_trans(root);
+ if (!root->fs_info->open_ioctl_trans)
+ wait_current_trans(root);
mutex_unlock(&root->fs_info->trans_mutex);
throttle_on_drops(root);
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