3.6.11.4 stable review patch. If anyone has any objections, please let me know. ------------------ From: Dmitry Monakhov [ Upstream commit 794446c6946513c684d448205fbd76fa35f38b72 ] The following race is possible: [kjournald2] other_task jbd2_journal_commit_transaction() j_state = T_FINISHED; spin_unlock(&journal->j_list_lock); ->jbd2_journal_remove_checkpoint() ->jbd2_journal_free_transaction(); ->kmem_cache_free(transaction) ->j_commit_callback(journal, transaction); -> USE_AFTER_FREE WARNING: at lib/list_debug.c:62 __list_del_entry+0x1c0/0x250() Hardware name: list_del corruption. prev->next should be ffff88019a4ec198, but was 6b6b6b6b6b6b6b6b Modules linked in: cpufreq_ondemand acpi_cpufreq freq_table mperf coretemp kvm_intel kvm crc32c_intel ghash_clmulni_intel microcode sg xhci_hcd button sd_mod crc_t10dif aesni_intel ablk_helper cryptd lrw aes_x86_64 xts gf128mul ahci libahci pata_acpi ata_generic dm_mirror dm_region_hash dm_log dm_mod Pid: 16400, comm: jbd2/dm-1-8 Tainted: G W 3.8.0-rc3+ #107 Call Trace: [] warn_slowpath_common+0xad/0xf0 [] warn_slowpath_fmt+0x46/0x50 [] ? ext4_journal_commit_callback+0x99/0xc0 [] __list_del_entry+0x1c0/0x250 [] ext4_journal_commit_callback+0x6f/0xc0 [] jbd2_journal_commit_transaction+0x23a6/0x2570 [] ? try_to_del_timer_sync+0x82/0xa0 [] ? del_timer_sync+0x91/0x1e0 [] kjournald2+0x19f/0x6a0 [] ? wake_up_bit+0x40/0x40 [] ? bit_spin_lock+0x80/0x80 [] kthread+0x10e/0x120 [] ? __init_kthread_worker+0x70/0x70 [] ret_from_fork+0x7c/0xb0 [] ? __init_kthread_worker+0x70/0x70 In order to demonstrace this issue one should mount ext4 with mount -o discard option on SSD disk. This makes callback longer and race window becomes wider. In order to fix this we should mark transaction as finished only after callbacks have completed Signed-off-by: Dmitry Monakhov Signed-off-by: "Theodore Ts'o" Cc: stable@vger.kernel.org Signed-off-by: Steven Rostedt --- fs/jbd2/commit.c | 50 ++++++++++++++++++++++++++++---------------------- include/linux/jbd2.h | 1 + 2 files changed, 29 insertions(+), 22 deletions(-) diff --git a/fs/jbd2/commit.c b/fs/jbd2/commit.c index af5280f..aa608d9 100644 --- a/fs/jbd2/commit.c +++ b/fs/jbd2/commit.c @@ -382,7 +382,7 @@ void jbd2_journal_commit_transaction(journal_t *journal) int space_left = 0; int first_tag = 0; int tag_flag; - int i, to_free = 0; + int i; int tag_bytes = journal_tag_bytes(journal); struct buffer_head *cbh = NULL; /* For transactional checksums */ __u32 crc32_sum = ~0; @@ -1108,7 +1108,7 @@ restart_loop: journal->j_stats.run.rs_blocks_logged += stats.run.rs_blocks_logged; spin_unlock(&journal->j_history_lock); - commit_transaction->t_state = T_FINISHED; + commit_transaction->t_state = T_COMMIT_CALLBACK; J_ASSERT(commit_transaction == journal->j_committing_transaction); journal->j_commit_sequence = commit_transaction->t_tid; journal->j_committing_transaction = NULL; @@ -1123,38 +1123,44 @@ restart_loop: journal->j_average_commit_time*3) / 4; else journal->j_average_commit_time = commit_time; + write_unlock(&journal->j_state_lock); - if (commit_transaction->t_checkpoint_list == NULL && - commit_transaction->t_checkpoint_io_list == NULL) { - __jbd2_journal_drop_transaction(journal, commit_transaction); - to_free = 1; + if (journal->j_checkpoint_transactions == NULL) { + journal->j_checkpoint_transactions = commit_transaction; + commit_transaction->t_cpnext = commit_transaction; + commit_transaction->t_cpprev = commit_transaction; } else { - if (journal->j_checkpoint_transactions == NULL) { - journal->j_checkpoint_transactions = commit_transaction; - commit_transaction->t_cpnext = commit_transaction; - commit_transaction->t_cpprev = commit_transaction; - } else { - commit_transaction->t_cpnext = - journal->j_checkpoint_transactions; - commit_transaction->t_cpprev = - commit_transaction->t_cpnext->t_cpprev; - commit_transaction->t_cpnext->t_cpprev = - commit_transaction; - commit_transaction->t_cpprev->t_cpnext = + commit_transaction->t_cpnext = + journal->j_checkpoint_transactions; + commit_transaction->t_cpprev = + commit_transaction->t_cpnext->t_cpprev; + commit_transaction->t_cpnext->t_cpprev = + commit_transaction; + commit_transaction->t_cpprev->t_cpnext = commit_transaction; - } } spin_unlock(&journal->j_list_lock); - + /* Drop all spin_locks because commit_callback may be block. + * __journal_remove_checkpoint() can not destroy transaction + * under us because it is not marked as T_FINISHED yet */ if (journal->j_commit_callback) journal->j_commit_callback(journal, commit_transaction); trace_jbd2_end_commit(journal, commit_transaction); jbd_debug(1, "JBD2: commit %d complete, head %d\n", journal->j_commit_sequence, journal->j_tail_sequence); - if (to_free) - jbd2_journal_free_transaction(commit_transaction); + write_lock(&journal->j_state_lock); + spin_lock(&journal->j_list_lock); + commit_transaction->t_state = T_FINISHED; + /* Recheck checkpoint lists after j_list_lock was dropped */ + if (commit_transaction->t_checkpoint_list == NULL && + commit_transaction->t_checkpoint_io_list == NULL) { + __jbd2_journal_drop_transaction(journal, commit_transaction); + jbd2_journal_free_transaction(commit_transaction); + } + spin_unlock(&journal->j_list_lock); + write_unlock(&journal->j_state_lock); wake_up(&journal->j_wait_done_commit); } diff --git a/include/linux/jbd2.h b/include/linux/jbd2.h index deee02a..ade60e7 100644 --- a/include/linux/jbd2.h +++ b/include/linux/jbd2.h @@ -498,6 +498,7 @@ struct transaction_s T_COMMIT, T_COMMIT_DFLUSH, T_COMMIT_JFLUSH, + T_COMMIT_CALLBACK, T_FINISHED } t_state; -- 1.7.10.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/