kill-the-BKL/reiserfs: lock only once in reiserfs_truncate_file

Impact: fix a deadlock

reiserfs_truncate_file() can be called from multiple context where
the write lock can be already hold or not.

This function also acquire (possibly recursively) the write
lock. Subsequent releases before sleeping will not actually release
the lock because we may be in more than one lock depth degree.

A typical case is:

reiserfs_file_release {
	acquire_the_lock()
	reiserfs_truncate_file()
		reacquire_the_lock()
		journal_begin() {
			do_journal_begin_r() {
				reiserfs_wait_on_write_block() {
					/*
					 * Not released because still one
					 * depth owned
					 */
					release_lock()
					wait_for_event()

At this stage the event never happen because the one which provides
it needs the write lock.

We use reiserfs_write_lock_once() here to ensure that we don't acquire the
write lock recursively.

Signed-off-by: Frederic Weisbecker <[email protected]>
Cc: Alessio Igor Bogani <[email protected]>
Cc: Jeff Mahoney <[email protected]>
Cc: Alexander Beregalov <[email protected]>
Cc: Chris Mason <[email protected]>
LKML-Reference: <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>

0 files changed, 0 insertions, 0 deletions