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jbd2: cleanup needed free block estimates when starting a transaction

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__jbd2_log_space_left() and jbd_space_needed() were kind of odd.
jbd_space_needed() accounted also credits needed for currently
committing transaction while it didn't account for credits needed for
control blocks.  __jbd2_log_space_left() then accounted for control
blocks as a fraction of free space.  Since results of these two
functions are always only compared against each other, this works
correct but is somewhat strange.  Move the estimates so that
jbd_space_needed() returns number of blocks needed for a transaction
including control blocks and __jbd2_log_space_left() returns free
space in the journal (with the committing transaction already
subtracted).  Rename functions to jbd2_log_space_left() and
jbd2_space_needed() while we are changing them.

Reviewed-by: Zheng Liu <wenqing.lz@taobao.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
This commit is contained in:
Jan Kara 2013-06-04 12:12:57 -04:00 committed by Theodore Ts'o
parent 2f387f849b
commit 76c3990456
4 changed files with 35 additions and 43 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

8
fs/jbd2/checkpoint.c
View file

@ -120,8 +120,8 @@ void __jbd2_log_wait_for_space(journal_t *journal)
int nblocks, space_left;
/* assert_spin_locked(&journal->j_state_lock); */
nblocks = jbd_space_needed(journal);
while (__jbd2_log_space_left(journal) < nblocks) {
nblocks = jbd2_space_needed(journal);
while (jbd2_log_space_left(journal) < nblocks) {
if (journal->j_flags & JBD2_ABORT)
return;
write_unlock(&journal->j_state_lock);
@ -140,8 +140,8 @@ void __jbd2_log_wait_for_space(journal_t *journal)
*/
write_lock(&journal->j_state_lock);
spin_lock(&journal->j_list_lock);
nblocks = jbd_space_needed(journal);
space_left = __jbd2_log_space_left(journal);
nblocks = jbd2_space_needed(journal);
space_left = jbd2_log_space_left(journal);
if (space_left < nblocks) {
int chkpt = journal->j_checkpoint_transactions != NULL;
tid_t tid = 0;

29
fs/jbd2/journal.c
View file

@ -477,35 +477,6 @@ int jbd2_journal_write_metadata_buffer(transaction_t *transaction,
* journal, so that we can begin checkpointing when appropriate.
*/
/*
* __jbd2_log_space_left: Return the number of free blocks left in the journal.
*
* Called with the journal already locked.
*
* Called under j_state_lock
*/
int __jbd2_log_space_left(journal_t *journal)
{
int left = journal->j_free;
/* assert_spin_locked(&journal->j_state_lock); */
/*
* Be pessimistic here about the number of those free blocks which
* might be required for log descriptor control blocks.
*/
#define MIN_LOG_RESERVED_BLOCKS 32 /* Allow for rounding errors */
left -= MIN_LOG_RESERVED_BLOCKS;
if (left <= 0)
return 0;
left -= (left >> 3);
return left;
}
/*
* Called with j_state_lock locked for writing.
* Returns true if a transaction commit was started.

9
fs/jbd2/transaction.c
View file

@ -283,12 +283,12 @@ static int start_this_handle(journal_t *journal, handle_t *handle,
* reduce the free space arbitrarily. Be careful to account for
* those buffers when checkpointing.
*/
if (__jbd2_log_space_left(journal) < jbd_space_needed(journal)) {
if (jbd2_log_space_left(journal) < jbd2_space_needed(journal)) {
jbd_debug(2, "Handle %p waiting for checkpoint...\n", handle);
atomic_sub(nblocks, &transaction->t_outstanding_credits);
read_unlock(&journal->j_state_lock);
write_lock(&journal->j_state_lock);
if (__jbd2_log_space_left(journal) < jbd_space_needed(journal))
if (jbd2_log_space_left(journal) < jbd2_space_needed(journal))
__jbd2_log_wait_for_space(journal);
write_unlock(&journal->j_state_lock);
goto repeat;
@ -306,7 +306,7 @@ static int start_this_handle(journal_t *journal, handle_t *handle,
jbd_debug(4, "Handle %p given %d credits (total %d, free %d)\n",
handle, nblocks,
atomic_read(&transaction->t_outstanding_credits),
__jbd2_log_space_left(journal));
jbd2_log_space_left(journal));
read_unlock(&journal->j_state_lock);
lock_map_acquire(&handle->h_lockdep_map);
@ -441,7 +441,8 @@ int jbd2_journal_extend(handle_t *handle, int nblocks)
goto unlock;
}
if (wanted > __jbd2_log_space_left(journal)) {
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);
goto unlock;

32
include/linux/jbd2.h
View file

@ -1220,7 +1220,6 @@ extern void jbd2_clear_buffer_revoked_flags(journal_t *journal);
* transitions on demand.
*/
int __jbd2_log_space_left(journal_t *); /* Called with journal locked */
int jbd2_log_start_commit(journal_t *journal, tid_t tid);
int __jbd2_log_start_commit(journal_t *journal, tid_t tid);
int jbd2_journal_start_commit(journal_t *journal, tid_t *tid);
@ -1290,17 +1289,38 @@ static inline int tid_geq(tid_t x, tid_t y)
extern int jbd2_journal_blocks_per_page(struct inode *inode);
extern size_t journal_tag_bytes(journal_t *journal);
/*
* 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 jbd_space_needed(journal_t *journal)
static inline int jbd2_space_needed(journal_t *journal)
{
int nblocks = journal->j_max_transaction_buffers;
if (journal->j_committing_transaction)
nblocks += atomic_read(&journal->j_committing_transaction->
t_outstanding_credits);
return nblocks;
return nblocks + (nblocks >> JBD2_CONTROL_BLOCKS_SHIFT);
}
/*
* Return number of free blocks in the log. Must be called under j_state_lock.
*/
static inline unsigned long jbd2_log_space_left(journal_t *journal)
{
/* Allow for rounding errors */
unsigned 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);
}
return free;
}
/*