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author | Sage Weil <sage@newdream.net> | 2008-08-04 14:41:27 (GMT) |
---|---|---|
committer | Chris Mason <chris.mason@oracle.com> | 2008-09-25 15:04:06 (GMT) |
commit | 9ca9ee09c176a814189063c8b88f75c8f8e4ad19 (patch) | |
tree | 3092ed3f5dd472e66a61da9306dfa6839604c42c /fs/btrfs/transaction.c | |
parent | 3117a77370b6cb902191568e4e647cdcba083d0a (diff) | |
download | linux-fsl-qoriq-9ca9ee09c176a814189063c8b88f75c8f8e4ad19.tar.xz |
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.c | 18 |
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); |