Re: [PATCH 1/2] jbd: allocate transacion from special cache

Manish Katiyar
2011-11-14T15:22:24Z

On Mon, Nov 14, 2011 at 4:53 AM, Jan Kara <jack@suse.cz> wrote:
> On Sun 13-11-11 19:29:31, Yongqiang Yang wrote:
>> transaction_t is 100 bytes under 32-bit systems. Transactions
>> allocated from general cache comsume 128 bytes. This patch
>> lets jbd allocates transacion from special cache.
>>
>> Signed-off-by: Yongqiang Yang <xiaoqiangnk@gmail.com>
>  Space saving isn't probably a good argument here since the number of
> transactions on the system is going to be rather low (a couple per ext3
> filesystem). The reason why I wanted this change for JBD2 is that it makes
> debugging of memory corruption of a transaction structure much easier (and
> I've been tracking down issues like this several times already).
>
> That being said, I don't find strong need to have this in ext3 and thus
> I'll take the change in jbd/ext3

I had submitted a similar patch for ext3, but it was rejected by
Andrew Morton. http://lists.openwall.net/linux-ext4/2011/06/13/15

> if Ted takes the similar change to
> jbd2/ext4 to keep compatibility. Manish Katiyar was working on it
> (http://comments.gmane.org/gmane.comp.file-systems.ext4/25884) but it seems
> it wasn't merged yet.
>
>                                                                        Honza
>
>> ---
>>  fs/jbd/checkpoint.c  |    2 +-
>>  fs/jbd/journal.c     |    3 +++
>>  fs/jbd/transaction.c |   31 +++++++++++++++++++++++++++++--
>>  include/linux/jbd.h  |    5 +++++
>>  4 files changed, 38 insertions(+), 3 deletions(-)
>>
>> diff --git a/fs/jbd/checkpoint.c b/fs/jbd/checkpoint.c
>> index f94fc48..4d98046 100644
>> --- a/fs/jbd/checkpoint.c
>> +++ b/fs/jbd/checkpoint.c
>> @@ -764,5 +764,5 @@ void __journal_drop_transaction(journal_t *journal, transaction_t *transaction)
>>
>>       trace_jbd_drop_transaction(journal, transaction);
>>       jbd_debug(1, "Dropping transaction %d, all done\n", transaction->t_tid);
>> -     kfree(transaction);
>> +     journal_free_transaction(transaction);
>>  }
>> diff --git a/fs/jbd/journal.c b/fs/jbd/journal.c
>> index 9fe061f..45ca982 100644
>> --- a/fs/jbd/journal.c
>> +++ b/fs/jbd/journal.c
>> @@ -2004,6 +2004,8 @@ static int __init journal_init_caches(void)
>>               ret = journal_init_journal_head_cache();
>>       if (ret == 0)
>>               ret = journal_init_handle_cache();
>> +     if (ret == 0)
>> +             ret = journal_init_transaction_cache();
>>       return ret;
>>  }
>>
>> @@ -2012,6 +2014,7 @@ static void journal_destroy_caches(void)
>>       journal_destroy_revoke_caches();
>>       journal_destroy_journal_head_cache();
>>       journal_destroy_handle_cache();
>> +     journal_destroy_transaction_cache();
>>  }
>>
>>  static int __init journal_init(void)
>> diff --git a/fs/jbd/transaction.c b/fs/jbd/transaction.c
>> index 7e59c6e..20d76f1 100644
>> --- a/fs/jbd/transaction.c
>> +++ b/fs/jbd/transaction.c
>> @@ -30,6 +30,32 @@
>>
>>  static void __journal_temp_unlink_buffer(struct journal_head *jh);
>>
>> +static struct kmem_cache *transaction_cache;
>> +int __init journal_init_transaction_cache(void)
>> +{
>> +     J_ASSERT(!transaction_cache);
>> +     transaction_cache = KMEM_CACHE(transaction_s,
>> +                                    SLAB_HWCACHE_ALIGN|SLAB_TEMPORARY);
>> +     if (transaction_cache)
>> +             return 0;
>> +     return -ENOMEM;
>> +}
>> +
>> +void __init journal_destroy_transaction_cache(void)
>> +{
>> +     if (transaction_cache) {
>> +             kmem_cache_destroy(transaction_cache);
>> +             transaction_cache = NULL;
>> +     }
>> +}
>> +
>> +void journal_free_transaction(transaction_t *transaction)
>> +{
>> +     if (unlikely(ZERO_OR_NULL_PTR(transaction)))
>> +             return;
>> +     kmem_cache_free(transaction_cache, transaction);
>> +}
>> +
>>  /*
>>   * get_transaction: obtain a new transaction_t object.
>>   *
>> @@ -100,11 +126,12 @@ static int start_this_handle(journal_t *journal, handle_t *handle)
>>
>>  alloc_transaction:
>>       if (!journal->j_running_transaction) {
>> -             new_transaction = kzalloc(sizeof(*new_transaction), GFP_NOFS);
>> +             new_transaction = kmem_cache_alloc(transaction_cache, GFP_NOFS);
>>               if (!new_transaction) {
>>                       congestion_wait(BLK_RW_ASYNC, HZ/50);
>>                       goto alloc_transaction;
>>               }
>> +             memset(new_transaction, 0, sizeof(*new_transaction));
>>       }
>>
>>       jbd_debug(3, "New handle %p going live.\n", handle);
>> @@ -233,7 +260,7 @@ repeat_locked:
>>       lock_map_acquire(&handle->h_lockdep_map);
>>  out:
>>       if (unlikely(new_transaction))          /* It's usually NULL */
>> -             kfree(new_transaction);
>> +             journal_free_transaction(new_transaction);
>>       return ret;
>>  }
>>
>> diff --git a/include/linux/jbd.h b/include/linux/jbd.h
>> index c7acdde..0f9f0b6 100644
>> --- a/include/linux/jbd.h
>> +++ b/include/linux/jbd.h
>> @@ -807,6 +807,11 @@ journal_write_metadata_buffer(transaction_t        *transaction,
>>  /* Transaction locking */
>>  extern void          __wait_on_journal (journal_t *);
>>
>> +/* Transaction cache support */
>> +extern void journal_destroy_transaction_cache(void);
>> +extern int  journal_init_transaction_cache(void);
>> +extern void journal_free_transaction(transaction_t *);
>> +
>>  /*
>>   * Journal locking.
>>   *
>> --
>> 1.7.5.1
>>
> --
> Jan Kara <jack@suse.cz>
> SUSE Labs, CR
> --
> To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>

--
Thanks -
Manish
--
To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html