From d9b01934d56a96d9f4ae2d6204d4ea78a36f5f36 Mon Sep 17 00:00:00 2001 From: Ted Ts'o Date: Sat, 30 Apr 2011 13:17:11 -0400 Subject: [PATCH] jbd: fix fsync() tid wraparound bug If an application program does not make any changes to the indirect blocks or extent tree, i_datasync_tid will not get updated. If there are enough commits (i.e., 2**31) such that tid_geq()'s calculations wrap, and there isn't a currently active transaction at the time of the fdatasync() call, this can end up triggering a BUG_ON in fs/jbd/commit.c: J_ASSERT(journal->j_running_transaction != NULL); It's pretty rare that this can happen, since it requires the use of fdatasync() plus *very* frequent and excessive use of fsync(). But with the right workload, it can. We fix this by replacing the use of tid_geq() with an equality test, since there's only one valid transaction id that is valid for us to start: namely, the currently running transaction (if it exists). CC: stable@kernel.org Reported-by: Martin_Zielinski@McAfee.com Signed-off-by: "Theodore Ts'o" Signed-off-by: Jan Kara --- Reading git-format-patch failed