Btrfs fallocate was incorrectly starting a transaction with a lock held
on the extent_io tree for the file, which could deadlock. Strictly
speaking it was using join_transaction which would be safe, but it is better
to move the transaction outside of the lock.
When preallocated extents are overwritten, btrfs_mark_buffer_dirty was
being called on an unlocked buffer. This was triggering an assertion and
oops because the lock is supposed to be held.
The bug was calling btrfs_mark_buffer_dirty on a leaf after btrfs_del_item had
been run. btrfs_del_item takes care of dirtying things, so the solution is a
to skip the btrfs_mark_buffer_dirty call in this case.
Signed-off-by: Chris Mason <chris.mason@oracle.com>
546888da82