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| author | Jan Kara <jack@suse.cz> | 2012-12-21 00:15:51 -0500 |
|---|---|---|
| committer | Theodore Ts'o <tytso@mit.edu> | 2012-12-21 00:15:51 -0500 |
| commit | d7961c7fa4d2e3c3f12be67e21ba8799b5a7238a (patch) | |
| tree | 3341ce3bdff7f2283e18f0cb02c438f421d746b0 /mm/mprotect.c | |
| parent | 261cb20cb2f0737a247aaf08dff7eb065e3e5b66 (diff) | |
| download | talos-obmc-linux-d7961c7fa4d2e3c3f12be67e21ba8799b5a7238a.tar.gz talos-obmc-linux-d7961c7fa4d2e3c3f12be67e21ba8799b5a7238a.zip | |
jbd2: fix assertion failure in jbd2_journal_flush()
The following race is possible between start_this_handle() and someone
calling jbd2_journal_flush().
Process A Process B
start_this_handle().
if (journal->j_barrier_count) # false
if (!journal->j_running_transaction) { #true
read_unlock(&journal->j_state_lock);
jbd2_journal_lock_updates()
jbd2_journal_flush()
write_lock(&journal->j_state_lock);
if (journal->j_running_transaction) {
# false
... wait for committing trans ...
write_unlock(&journal->j_state_lock);
...
write_lock(&journal->j_state_lock);
if (!journal->j_running_transaction) { # true
jbd2_get_transaction(journal, new_transaction);
write_unlock(&journal->j_state_lock);
goto repeat; # eventually blocks on j_barrier_count > 0
...
J_ASSERT(!journal->j_running_transaction);
# fails
We fix the race by rechecking j_barrier_count after reacquiring j_state_lock
in exclusive mode.
Reported-by: yjwsignal@empal.com
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Cc: stable@vger.kernel.org
Diffstat (limited to 'mm/mprotect.c')
0 files changed, 0 insertions, 0 deletions
