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Date: Mon, 14 Nov 2011 07:22:03 -0800
From: Manish Katiyar <mkatiyar@...il.com>
To: Jan Kara <jack@...e.cz>
Cc: Yongqiang Yang <xiaoqiangnk@...il.com>, linux-ext4@...r.kernel.org
Subject: Re: [PATCH 1/2] jbd: allocate transacion from special cache
On Mon, Nov 14, 2011 at 4:53 AM, Jan Kara <jack@...e.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@...il.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@...e.cz>
> SUSE Labs, CR
> --
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>
--
Thanks -
Manish
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