| Message ID | 20230109134545.2234414-1-chengzhihao1@huawei.com |
|---|---|
| State | Superseded |
| Headers | show |
| Series | [-next,v3] jbd2: Fix data missing when reusing bh which is ready to be checkpointed | expand |
On Mon 09-01-23 21:45:45, 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@kernel.org> > Signed-off-by: Zhihao Cheng <chengzhihao1@huawei.com> > Signed-off-by: zhanchengbin <zhanchengbin1@huawei.com> > Suggested-by: Jan Kara <jack@suse.cz> Great, the patch looks good. Feel free to add: Reviewed-by: Jan Kara <jack@suse.cz> Just a suggestion for rephrasing of the comment below > - /* > - * 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); > + /* > + * Setting jbddirty after clearing buffer dirty is necessary. > + * Function jbd2_journal_restart() could keep buffer on > + * BJ_Reserved list until the transaction committing, then the > + * buffer won't be dirtied by jbd2_journal_refile_buffer() > + * after committing, the buffer couldn't fall on disk even > + * last checkpoint finished, which may corrupt filesystem. > + */ As far as I understand you want to say: /* * 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); > } Honza
> On Mon 09-01-23 21:45:45, Zhihao Cheng wrote >> Following process will make data lost and could lead to a filesystem>> corrupted problem:>> [...] > Just a suggestion for rephrasing of the comment below > >> - /* >> - * 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); >> + /* >> + * Setting jbddirty after clearing buffer dirty is necessary. >> + * Function jbd2_journal_restart() could keep buffer on >> + * BJ_Reserved list until the transaction committing, then the >> + * buffer won't be dirtied by jbd2_journal_refile_buffer() >> + * after committing, the buffer couldn't fall on disk even >> + * last checkpoint finished, which may corrupt filesystem. >> + */ > > As far as I understand you want to say: > /* > * 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); >> } > Yes. The comment looks better than v3.
diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c index 6a404ac1c178..2fbe0f201b29 100644 --- a/fs/jbd2/transaction.c +++ b/fs/jbd2/transaction.c @@ -1010,36 +1010,29 @@ 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); + /* + * Setting jbddirty after clearing buffer dirty is necessary. + * Function jbd2_journal_restart() could keep buffer on + * BJ_Reserved list until the transaction committing, then the + * buffer won't be dirtied by jbd2_journal_refile_buffer() + * after committing, the buffer couldn't fall on disk even + * last checkpoint finished, which may corrupt filesystem. + */ 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 +1042,10 @@ 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 +1069,24 @@ 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
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@kernel.org> Signed-off-by: Zhihao Cheng <chengzhihao1@huawei.com> Signed-off-by: zhanchengbin <zhanchengbin1@huawei.com> Suggested-by: Jan Kara <jack@suse.cz> --- 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. fs/jbd2/transaction.c | 51 +++++++++++++++++++++++++------------------ 1 file changed, 30 insertions(+), 21 deletions(-)