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Date: Wed, 8 Jun 2011 18:49:03 +0200
From: Jan Kara <jack@...e.cz>
To: Manish Katiyar <mkatiyar@...il.com>
Cc: jack@...e.cz, tytso@....edu, linux-ext4@...r.kernel.org
Subject: Re: [PATCH] jbd2:Make journal transaction allocations come from
its own cache.
On Sun 05-06-11 01:28:30, Manish Katiyar wrote:
> Add a cache for jbd2 journal transaction allocations. This also
> helps to leverage fault-injection framework to test various memory
> allocation failures in the jbd2 layer.
>
> Signed-off-by: Manish Katiyar <mkatiyar@...il.com>
> ---
> fs/jbd2/checkpoint.c | 2 +-
> fs/jbd2/commit.c | 2 +-
> fs/jbd2/journal.c | 25 +++++++++++++++++++++++++
> fs/jbd2/transaction.c | 7 ++++---
> include/linux/jbd2.h | 21 +++++++++++++++++++++
> 5 files changed, 52 insertions(+), 5 deletions(-)
>
> diff --git a/fs/jbd2/checkpoint.c b/fs/jbd2/checkpoint.c
> index 6a79fd0..6f554ce 100644
> --- a/fs/jbd2/checkpoint.c
> +++ b/fs/jbd2/checkpoint.c
> @@ -716,7 +716,7 @@ int __jbd2_journal_remove_checkpoint(struct journal_head *jh)
> transaction->t_tid, stats);
>
> __jbd2_journal_drop_transaction(journal, transaction);
> - kfree(transaction);
> + jbd2_free_transaction(transaction);
>
> /* Just in case anybody was waiting for more transactions to be
> checkpointed... */
> diff --git a/fs/jbd2/commit.c b/fs/jbd2/commit.c
> index 7f21cf3..8e33d84 100644
> --- a/fs/jbd2/commit.c
> +++ b/fs/jbd2/commit.c
> @@ -1037,7 +1037,7 @@ restart_loop:
> jbd_debug(1, "JBD: commit %d complete, head %d\n",
> journal->j_commit_sequence, journal->j_tail_sequence);
> if (to_free)
> - kfree(commit_transaction);
> + jbd2_free_transaction(commit_transaction);
>
> wake_up(&journal->j_wait_done_commit);
> }
> diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
> index 9a78269..c0ec463 100644
> --- a/fs/jbd2/journal.c
> +++ b/fs/jbd2/journal.c
> @@ -95,6 +95,7 @@ EXPORT_SYMBOL(jbd2_journal_init_jbd_inode);
> EXPORT_SYMBOL(jbd2_journal_release_jbd_inode);
> EXPORT_SYMBOL(jbd2_journal_begin_ordered_truncate);
> EXPORT_SYMBOL(jbd2_inode_cache);
> +EXPORT_SYMBOL(jbd2_transaction_cache);
>
> static int journal_convert_superblock_v1(journal_t *, journal_superblock_t *);
> static void __journal_abort_soft (journal_t *journal, int errno);
> @@ -2371,6 +2372,27 @@ static void jbd2_journal_destroy_handle_cache(void)
>
> }
>
> +struct kmem_cache *jbd2_transaction_cache;
> +
> +static int journal_init_transaction_cache(void)
> +{
> + J_ASSERT(jbd2_transaction_cache == NULL);
> + jbd2_transaction_cache = kmem_cache_create("jbd2_transaction",
> + sizeof(transaction_t),
> + 0, SLAB_TEMPORARY, NULL);
Transactions are not really short-lived in the memory-management sense I
think. They usually live for seconds while I'd understand 'short-lived' to
mean a milisecond or less. So just drop this flag (it doesn't do anything
these days anyway).
> + if (jbd2_transaction_cache == NULL) {
> + printk(KERN_EMERG "JBD2: failed to create transaction cache\n");
> + return -ENOMEM;
> + }
> + return 0;
> +}
> +
> +static void jbd2_journal_destroy_transaction_cache(void)
> +{
> + if (jbd2_transaction_cache)
How can this happen?
> + kmem_cache_destroy(jbd2_transaction_cache);
> +}
> +
> /*
> * Module startup and shutdown
> */
> @@ -2384,6 +2406,8 @@ static int __init journal_init_caches(void)
> ret = journal_init_jbd2_journal_head_cache();
> if (ret == 0)
> ret = journal_init_handle_cache();
> + if (ret == 0)
> + ret = journal_init_transaction_cache();
> return ret;
> }
>
> @@ -2392,6 +2416,7 @@ static void jbd2_journal_destroy_caches(void)
> jbd2_journal_destroy_revoke_caches();
> jbd2_journal_destroy_jbd2_journal_head_cache();
> jbd2_journal_destroy_handle_cache();
> + jbd2_journal_destroy_transaction_cache();
> jbd2_journal_destroy_slabs();
> }
>
> diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c
> index 3eec82d..58fbec7 100644
> --- a/fs/jbd2/transaction.c
> +++ b/fs/jbd2/transaction.c
> @@ -131,7 +131,7 @@ 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_mask);
> + new_transaction = jbd2_alloc_transaction(gfp_mask);
> if (!new_transaction) {
> /*
> * If __GFP_FS is not present, then we may be
> @@ -160,7 +160,7 @@ repeat:
> if (is_journal_aborted(journal) ||
> (journal->j_errno != 0 && !(journal->j_flags & JBD2_ACK_ERR))) {
> read_unlock(&journal->j_state_lock);
> - kfree(new_transaction);
> + jbd2_free_transaction(new_transaction);
> return -EROFS;
> }
>
> @@ -282,7 +282,8 @@ repeat:
> read_unlock(&journal->j_state_lock);
>
> lock_map_acquire(&handle->h_lockdep_map);
> - kfree(new_transaction);
> + jbd2_free_transaction(new_transaction);
> +
> return 0;
> }
>
> diff --git a/include/linux/jbd2.h b/include/linux/jbd2.h
> index 4ecb7b1..df7f101 100644
> --- a/include/linux/jbd2.h
> +++ b/include/linux/jbd2.h
> @@ -1184,6 +1184,27 @@ static inline void jbd2_free_handle(handle_t *handle)
> }
>
> /*
> + * transaction management
> + */
> +extern struct kmem_cache *jbd2_transaction_cache;
> +
> +static inline transaction_t *jbd2_alloc_transaction(gfp_t gfp_flags)
> +{
> + return kmem_cache_zalloc(jbd2_transaction_cache, gfp_flags);
> +}
> +
> +static inline void jbd2_free_transaction(transaction_t *transaction)
> +{
> + if (transaction) {
> +#ifdef CONFIG_JBD2_DEBUG
> + memset(transaction, JBD2_POISON_FREE, sizeof(*transaction));
> +#endif
No need for this - CONFIG_DEBUG_SLAB does this for you...
> + kmem_cache_free(jbd2_transaction_cache, transaction);
> + }
> +}
> +
> +
> +/*
> * jbd2_inode management (optional, for those file systems that want to use
> * dynamically allocated jbd2_inode structures)
> */
Otherwise the patch looks OK to me.
Honza
--
Jan Kara <jack@...e.cz>
SUSE Labs, CR
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