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jbd2: Account descriptor blocks into t_outstanding_credits 

Currently, journal descriptor blocks were not accounted in
transaction->t_outstanding_credits and we were just leaving some slack
space in the journal for them (in jbd2_log_space_left() and
jbd2_space_needed()). This is making proper accounting (and reservation
we want to add) of descriptor blocks difficult so switch to accounting
descriptor blocks in transaction->t_outstanding_credits and just reserve
the same amount of credits in t_outstanding credits for journal
descriptor blocks when creating transaction.

Signed-off-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20191105164437.32602-18-jack@suse.cz
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
This commit is contained in:
Jan Kara 2019-11-05 17:44:24 +01:00 committed by Theodore Ts'o
parent ec8b6f600e
commit 9f356e5a4f
4 changed files with 24 additions and 25 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
fs/jbd2/commit.c
View File

@ -560,8 +560,7 @@ void jbd2_journal_commit_transaction(journal_t *journal)
stats.run.rs_logging = jiffies;
stats.run.rs_flushing = jbd2_time_diff(stats.run.rs_flushing,
stats.run.rs_logging);
stats.run.rs_blocks =
atomic_read(&commit_transaction->t_outstanding_credits);
stats.run.rs_blocks = commit_transaction->t_nr_buffers;
stats.run.rs_blocks_logged = 0;
J_ASSERT(commit_transaction->t_nr_buffers <=
@ -889,6 +888,9 @@ start_journal_io:
if (err)
jbd2_journal_abort(journal, err);
WARN_ON_ONCE(
atomic_read(&commit_transaction->t_outstanding_credits) < 0);
/*
* Now disk caches for filesystem device are flushed so we are safe to
* erase checkpointed transactions from the log by updating journal

1
fs/jbd2/journal.c
View File

@ -840,6 +840,7 @@ jbd2_journal_get_descriptor_buffer(transaction_t *transaction, int type)
bh = __getblk(journal->j_dev, blocknr, journal->j_blocksize);
if (!bh)
return NULL;
atomic_dec(&transaction->t_outstanding_credits);
lock_buffer(bh);
memset(bh->b_data, 0, journal->j_blocksize);
header = (journal_header_t *)bh->b_data;

20
fs/jbd2/transaction.c
View File

@ -62,6 +62,17 @@ void jbd2_journal_free_transaction(transaction_t *transaction)
kmem_cache_free(transaction_cache, transaction);
}
/*
* We reserve t_outstanding_credits >> JBD2_CONTROL_BLOCKS_SHIFT for
* transaction descriptor blocks.
*/
#define JBD2_CONTROL_BLOCKS_SHIFT 5
static int jbd2_descriptor_blocks_per_trans(journal_t *journal)
{
return journal->j_max_transaction_buffers >> JBD2_CONTROL_BLOCKS_SHIFT;
}
/*
* jbd2_get_transaction: obtain a new transaction_t object.
*
@ -88,6 +99,7 @@ static void jbd2_get_transaction(journal_t *journal,
spin_lock_init(&transaction->t_handle_lock);
atomic_set(&transaction->t_updates, 0);
atomic_set(&transaction->t_outstanding_credits,
jbd2_descriptor_blocks_per_trans(journal) +
atomic_read(&journal->j_reserved_credits));
atomic_set(&transaction->t_handle_count, 0);
INIT_LIST_HEAD(&transaction->t_inode_list);
@ -634,14 +646,6 @@ int jbd2_journal_extend(handle_t *handle, int nblocks)
goto unlock;
}
if (wanted + (wanted >> JBD2_CONTROL_BLOCKS_SHIFT) >
jbd2_log_space_left(journal)) {
jbd_debug(3, "denied handle %p %d blocks: "
"insufficient log space\n", handle, nblocks);
atomic_sub(nblocks, &transaction->t_outstanding_credits);
goto unlock;
}
trace_jbd2_handle_extend(journal->j_fs_dev->bd_dev,
transaction->t_tid,
handle->h_type, handle->h_line_no,

22
include/linux/jbd2.h
View File

@ -681,8 +681,10 @@ struct transaction_s
atomic_t t_updates;
/*
* Number of buffers reserved for use by all handles in this transaction
* handle but not yet modified. [none]
* Number of blocks reserved for this transaction in the journal.
* This is including all credits reserved when starting transaction
* handles as well as all journal descriptor blocks needed for this
* transaction. [none]
*/
atomic_t t_outstanding_credits;
@ -1560,20 +1562,13 @@ static inline int jbd2_journal_has_csum_v2or3(journal_t *journal)
return journal->j_chksum_driver != NULL;
}
/*
* We reserve t_outstanding_credits >> JBD2_CONTROL_BLOCKS_SHIFT for
* transaction control blocks.
*/
#define JBD2_CONTROL_BLOCKS_SHIFT 5
/*
* Return the minimum number of blocks which must be free in the journal
* before a new transaction may be started. Must be called under j_state_lock.
*/
static inline int jbd2_space_needed(journal_t *journal)
{
int nblocks = journal->j_max_transaction_buffers;
return nblocks + (nblocks >> JBD2_CONTROL_BLOCKS_SHIFT);
return journal->j_max_transaction_buffers;
}
/*
@ -1585,11 +1580,8 @@ static inline unsigned long jbd2_log_space_left(journal_t *journal)
long free = journal->j_free - 32;
if (journal->j_committing_transaction) {
unsigned long committing = atomic_read(&journal->
j_committing_transaction->t_outstanding_credits);
/* Transaction + control blocks */
free -= committing + (committing >> JBD2_CONTROL_BLOCKS_SHIFT);
free -= atomic_read(&journal->
j_committing_transaction->t_outstanding_credits);
}
return max_t(long, free, 0);
}