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Message-Id: <1365456754-29373-10-git-send-email-jack@suse.cz>
Date: Mon, 8 Apr 2013 23:32:14 +0200
From: Jan Kara <jack@...e.cz>
To: Ted Tso <tytso@....edu>
Cc: linux-ext4@...r.kernel.org, Jan Kara <jack@...e.cz>
Subject: [PATCH 09/29] jbd2: Cleanup needed free block estimates when starting a transaction
__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.
Signed-off-by: Jan Kara <jack@...e.cz>
---
fs/jbd2/checkpoint.c | 8 ++++----
fs/jbd2/journal.c | 29 -----------------------------
fs/jbd2/transaction.c | 9 +++++----
include/linux/jbd2.h | 32 ++++++++++++++++++++++++++------
4 files changed, 35 insertions(+), 43 deletions(-)
diff --git a/fs/jbd2/checkpoint.c b/fs/jbd2/checkpoint.c
index 65ec076..a572383 100644
--- a/fs/jbd2/checkpoint.c
+++ b/fs/jbd2/checkpoint.c
@@ -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;
diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
index e9a9cdb..e6f14e0 100644
--- a/fs/jbd2/journal.c
+++ b/fs/jbd2/journal.c
@@ -480,35 +480,6 @@ repeat:
*/
/*
- * __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.
*/
diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c
index 74cfbd3..aee40c9 100644
--- a/fs/jbd2/transaction.c
+++ b/fs/jbd2/transaction.c
@@ -283,12 +283,12 @@ repeat:
* 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 @@ repeat:
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);
@@ -442,7 +442,8 @@ 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;
diff --git a/include/linux/jbd2.h b/include/linux/jbd2.h
index be5115f..9197d1b 100644
--- a/include/linux/jbd2.h
+++ b/include/linux/jbd2.h
@@ -1219,7 +1219,6 @@ 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);
@@ -1289,16 +1288,37 @@ 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;
}
/*
--
1.7.1
--
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