On Tue 10-01-23 09:53:27, Zhihao Cheng wrote: > Following process will make data lost and could lead to a filesystem > corrupted problem: > > 1. jh(bh) is inserted into T1->t_checkpoint_list, bh is dirty, and > jh->b_transaction = NULL > 2. T1 is added into journal->j_checkpoint_transactions. > 3. Get bh prepare to write while doing checkpoing: > PA PB > do_get_write_access jbd2_log_do_checkpoint > spin_lock(&jh->b_state_lock) > if (buffer_dirty(bh)) > clear_buffer_dirty(bh) // clear buffer dirty > set_buffer_jbddirty(bh) > transaction = > journal->j_checkpoint_transactions > jh = transaction->t_checkpoint_list > if (!buffer_dirty(bh)) > __jbd2_journal_remove_checkpoint(jh) > // bh won't be flushed > jbd2_cleanup_journal_tail > __jbd2_journal_file_buffer(jh, transaction, BJ_Reserved) > 4. Aborting journal/Power-cut before writing latest bh on journal area. > > In this way we get a corrupted filesystem with bh's data lost. > > Fix it by moving the clearing of buffer_dirty bit just before the call > to __jbd2_journal_file_buffer(), both bit clearing and jh->b_transaction > assignment are under journal->j_list_lock locked, so that > jbd2_log_do_checkpoint() will wait until jh's new transaction fininshed > even bh is currently not dirty. And journal_shrink_one_cp_list() won't > remove jh from checkpoint list if the buffer head is reused in > do_get_write_access(). > > Fetch a reproducer in [Link]. > > Link: https://bugzilla.kernel.org/show_bug.cgi?id=216898 > Cc: <stable@xxxxxxxxxx> > Signed-off-by: Zhihao Cheng <chengzhihao1@xxxxxxxxxx> > Signed-off-by: zhanchengbin <zhanchengbin1@xxxxxxxxxx> > Suggested-by: Jan Kara <jack@xxxxxxx> The patch looks good to me! Feel free to add: Reviewed-by: Jan Kara <jack@xxxxxxx> Honza > --- > v1->v2: Adopt Jan's suggestion, move the clearing of buffer_dirty bit > and __jbd2_journal_file_buffer() inside journal->j_list_lock > locking area. > v2->v3: Remove redundant assertions in in branch 'if (jh->b_transaction)' > Add reproducer link in commit message. > v3->v4: Rephrase the comment for set_buffer_jbddirty(). > fs/jbd2/transaction.c | 50 +++++++++++++++++++++++++------------------ > 1 file changed, 29 insertions(+), 21 deletions(-) > > diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c > index 6a404ac1c178..15de1385012e 100644 > --- a/fs/jbd2/transaction.c > +++ b/fs/jbd2/transaction.c > @@ -1010,36 +1010,28 @@ do_get_write_access(handle_t *handle, struct journal_head *jh, > * ie. locked but not dirty) or tune2fs (which may actually have > * the buffer dirtied, ugh.) */ > > - if (buffer_dirty(bh)) { > + if (buffer_dirty(bh) && jh->b_transaction) { > + warn_dirty_buffer(bh); > /* > - * First question: is this buffer already part of the current > - * transaction or the existing committing transaction? > - */ > - if (jh->b_transaction) { > - J_ASSERT_JH(jh, > - jh->b_transaction == transaction || > - jh->b_transaction == > - journal->j_committing_transaction); > - if (jh->b_next_transaction) > - J_ASSERT_JH(jh, jh->b_next_transaction == > - transaction); > - warn_dirty_buffer(bh); > - } > - /* > - * In any case we need to clean the dirty flag and we must > - * do it under the buffer lock to be sure we don't race > - * with running write-out. > + * We need to clean the dirty flag and we must do it under the > + * buffer lock to be sure we don't race with running write-out. > */ > JBUFFER_TRACE(jh, "Journalling dirty buffer"); > clear_buffer_dirty(bh); > + /* > + * The buffer is going to be added to BJ_Reserved list now and > + * nothing guarantees jbd2_journal_dirty_metadata() will be > + * ever called for it. So we need to set jbddirty bit here to > + * make sure the buffer is dirtied and written out when the > + * journaling machinery is done with it. > + */ > set_buffer_jbddirty(bh); > } > > - unlock_buffer(bh); > - > error = -EROFS; > if (is_handle_aborted(handle)) { > spin_unlock(&jh->b_state_lock); > + unlock_buffer(bh); > goto out; > } > error = 0; > @@ -1049,8 +1041,10 @@ do_get_write_access(handle_t *handle, struct journal_head *jh, > * b_next_transaction points to it > */ > if (jh->b_transaction == transaction || > - jh->b_next_transaction == transaction) > + jh->b_next_transaction == transaction) { > + unlock_buffer(bh); > goto done; > + } > > /* > * this is the first time this transaction is touching this buffer, > @@ -1074,10 +1068,24 @@ do_get_write_access(handle_t *handle, struct journal_head *jh, > */ > smp_wmb(); > spin_lock(&journal->j_list_lock); > + if (test_clear_buffer_dirty(bh)) { > + /* > + * Execute buffer dirty clearing and jh->b_transaction > + * assignment under journal->j_list_lock locked to > + * prevent bh being removed from checkpoint list if > + * the buffer is in an intermediate state (not dirty > + * and jh->b_transaction is NULL). > + */ > + JBUFFER_TRACE(jh, "Journalling dirty buffer"); > + set_buffer_jbddirty(bh); > + } > __jbd2_journal_file_buffer(jh, transaction, BJ_Reserved); > spin_unlock(&journal->j_list_lock); > + unlock_buffer(bh); > goto done; > } > + unlock_buffer(bh); > + > /* > * If there is already a copy-out version of this buffer, then we don't > * need to make another one > -- > 2.31.1 > -- Jan Kara <jack@xxxxxxxx> SUSE Labs, CR
