tree 377bea15d7bbcc73f800c0be9938d69000ad09e8
parent 54930dfeb46e978b447af0fb8ab4e181c1bf9d7a
author Jeff Mahoney <jeffm@suse.com> 1498164454 -0400
committer Jan Kara <jack@suse.cz> 1498203630 +0200

reiserfs: fix race in prealloc discard

The main loop in __discard_prealloc is protected by the reiserfs write lock
which is dropped across schedules like the BKL it replaced.  The problem is
that it checks the value, calls a routine that schedules, and then adjusts
the state.  As a result, two threads that are calling
reiserfs_prealloc_discard at the same time can race when one calls
reiserfs_free_prealloc_block, the lock is dropped, and the other calls
reiserfs_free_prealloc_block with the same block number.  In the right
circumstances, it can cause the prealloc count to go negative.

Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Signed-off-by: Jan Kara <jack@suse.cz>