From: OGAWA Hirofumi Subject: [PATCH v2] ext4/jbd2: Fix FS corruption possibility on umount path Date: Sun, 28 Feb 2016 23:24:51 +0900 Message-ID: <87a8mk6hfw.fsf@mail.parknet.co.jp> Mime-Version: 1.0 Content-Type: text/plain Cc: linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org To: "Theodore Ts'o" Return-path: Sender: linux-fsdevel-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org On umount path, jbd2_journal_destroy() writes latest transaction ID (->j_tail_sequence) to be used at next mount. The bug is that ->j_tail_sequence is not holding latest transaction ID in some cases. So, at next mount, there is chance to conflict with remaining (not overwritten yet) transactions. mount (id=10) write transaction (id=11) write transaction (id=12) umount (id=10) <= the bug doesn't write latest ID mount (id=10) write transaction (id=11) crash mount [recovery process] transaction (id=11) transaction (id=12) <= valid transaction ID, but old commit must not replay Like above, this bug become the cause of recovery failure, or FS corruption. So why ->j_tail_sequence doesn't point latest ID? Because if checkpoint transactions was reclaimed by memory pressure (i.e. bdev_try_to_free_page()), then ->j_tail_sequence is not updated. (And another case is, __jbd2_journal_clean_checkpoint_list() is called with empty transaction.) So in above cases, ->j_tail_sequence is not pointing latest transaction ID at umount path. Plus, REQ_FLUSH for checkpoint is not done too. So, to fix this problem with minimum changes, this patch updates ->j_tail_sequence, and issue REQ_FLUSH. (With more complex changes, some optimizations would be possible to avoid unnecessary REQ_FLUSH for example though.) BTW, journal->j_tail_sequence = ++journal->j_transaction_sequence; Increment of ->j_transaction_sequence seems to be unnecessary, but ext3 does this. v2: Fix "make htmldocs" warning Signed-off-by: OGAWA Hirofumi Cc: stable@vger.kernel.org --- fs/jbd2/journal.c | 17 ++++++++++++----- 1 file changed, 12 insertions(+), 5 deletions(-) diff -puN fs/jbd2/journal.c~ext4-umount-fix fs/jbd2/journal.c --- linux/fs/jbd2/journal.c~ext4-umount-fix 2016-02-28 10:16:41.997093008 +0900 +++ linux-hirofumi/fs/jbd2/journal.c 2016-02-28 23:01:25.865647233 +0900 @@ -1408,11 +1408,12 @@ out: /** * jbd2_mark_journal_empty() - Mark on disk journal as empty. * @journal: The journal to update. + * @write_op: With which operation should we write the journal sb * * Update a journal's dynamic superblock fields to show that journal is empty. * Write updated superblock to disk waiting for IO to complete. */ -static void jbd2_mark_journal_empty(journal_t *journal) +static void jbd2_mark_journal_empty(journal_t *journal, int write_op) { journal_superblock_t *sb = journal->j_superblock; @@ -1430,7 +1431,7 @@ static void jbd2_mark_journal_empty(jour sb->s_start = cpu_to_be32(0); read_unlock(&journal->j_state_lock); - jbd2_write_superblock(journal, WRITE_FUA); + jbd2_write_superblock(journal, write_op); /* Log is no longer empty */ write_lock(&journal->j_state_lock); @@ -1716,7 +1717,13 @@ int jbd2_journal_destroy(journal_t *jour if (journal->j_sb_buffer) { if (!is_journal_aborted(journal)) { mutex_lock(&journal->j_checkpoint_mutex); - jbd2_mark_journal_empty(journal); + + write_lock(&journal->j_state_lock); + journal->j_tail_sequence = + ++journal->j_transaction_sequence; + write_unlock(&journal->j_state_lock); + + jbd2_mark_journal_empty(journal, WRITE_FLUSH_FUA); mutex_unlock(&journal->j_checkpoint_mutex); } else err = -EIO; @@ -1975,7 +1982,7 @@ int jbd2_journal_flush(journal_t *journa * the magic code for a fully-recovered superblock. Any future * commits of data to the journal will restore the current * s_start value. */ - jbd2_mark_journal_empty(journal); + jbd2_mark_journal_empty(journal, WRITE_FUA); mutex_unlock(&journal->j_checkpoint_mutex); write_lock(&journal->j_state_lock); J_ASSERT(!journal->j_running_transaction); @@ -2021,7 +2028,7 @@ int jbd2_journal_wipe(journal_t *journal if (write) { /* Lock to make assertions happy... */ mutex_lock(&journal->j_checkpoint_mutex); - jbd2_mark_journal_empty(journal); + jbd2_mark_journal_empty(journal, WRITE_FUA); mutex_unlock(&journal->j_checkpoint_mutex); } _ -- OGAWA Hirofumi