diff options
| author | Josef Bacik <jbacik@fusionio.com> | 2012-09-14 11:22:38 -0400 |
|---|---|---|
| committer | Chris Mason <chris.mason@fusionio.com> | 2012-10-04 09:39:58 -0400 |
| commit | 98114659e0d467e2c0ee6f24f2429329328fc312 (patch) | |
| tree | 6286d0eb87f22cc51a6f38503f6e82beb5fc0dfd /fs/btrfs | |
| parent | 6bbe3a9c805fcb8cd8d396dafd32078181a7cdd5 (diff) | |
Btrfs: fix race with freeze and free space inodes
So we start our freeze, somebody comes in and does an fsync() on a file
where we have to commit a transaction for whatever reason, and we will
deadlock because the freeze is waiting on FS_FREEZE people to stop writing
to the file system, but the transaction is waiting for its free space inodes
to be written out, which are in turn waiting on sb_start_intwrite while
trying to write the file extents. To fix this we'll just skip the
sb_start_intwrite() if we TRANS_JOIN_NOLOCK since we're being waited on by a
transaction commit so we're safe wrt to freeze and this will keep us from
deadlocking. Thanks,
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Diffstat (limited to 'fs/btrfs')
| -rw-r--r-- | fs/btrfs/transaction.c | 13 |
1 files changed, 11 insertions, 2 deletions
diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c index c9265a603488..a4fe5494d01b 100644 --- a/fs/btrfs/transaction.c +++ b/fs/btrfs/transaction.c @@ -342,7 +342,15 @@ again: if (!h) return ERR_PTR(-ENOMEM); - if (!__sb_start_write(root->fs_info->sb, SB_FREEZE_FS, false)) { + /* + * If we are JOIN_NOLOCK we're already committing a transaction and + * waiting on this guy, so we don't need to do the sb_start_intwrite + * because we're already holding a ref. We need this because we could + * have raced in and did an fsync() on a file which can kick a commit + * and then we deadlock with somebody doing a freeze. + */ + if (type != TRANS_JOIN_NOLOCK && + !__sb_start_write(root->fs_info->sb, SB_FREEZE_FS, false)) { if (type == TRANS_JOIN_FREEZE) return ERR_PTR(-EPERM); sb_start_intwrite(root->fs_info->sb); @@ -601,7 +609,8 @@ static int __btrfs_end_transaction(struct btrfs_trans_handle *trans, } } - sb_end_intwrite(root->fs_info->sb); + if (lock) + sb_end_intwrite(root->fs_info->sb); WARN_ON(cur_trans != info->running_transaction); WARN_ON(atomic_read(&cur_trans->num_writers) < 1); |