From: Alex Tomas <alex@clusterfs.com>
during truncate ext3 calls journal_forget() for freed blocks, but before
these blocks go to the transaction and jbd reserves space in log for them
(->t_outstanding_credits). also, journal_forget() removes these blocks
from the transaction, but doesn't correct log space reservation. for
example, removal of 500MB file reserves 136 blocks, but only 10 blocks go
to the log. a commit is expensive and correct reservation allows us to
avoid needless commits. here is the patch. tested on UP.
Signed-off-by: Alex Tomas <alex@clusterfs.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
---
25-akpm/fs/jbd/transaction.c | 10 +++++++++-
1 files changed, 9 insertions(+), 1 deletion(-)
diff -puN fs/jbd/transaction.c~jbd-log-space-management-optimization fs/jbd/transaction.c
--- 25/fs/jbd/transaction.c~jbd-log-space-management-optimization 2005-03-07 20:41:35.000000000 -0800
+++ 25-akpm/fs/jbd/transaction.c 2005-03-07 20:41:35.000000000 -0800
@@ -1187,6 +1187,7 @@ int journal_forget (handle_t *handle, st
transaction_t *transaction = handle->h_transaction;
journal_t *journal = transaction->t_journal;
struct journal_head *jh;
+ int drop_reserve = 0;
int err = 0;
BUFFER_TRACE(bh, "entry");
@@ -1224,6 +1225,7 @@ int journal_forget (handle_t *handle, st
JBUFFER_TRACE(jh, "belongs to current transaction: unfile");
__journal_unfile_buffer(jh);
+ drop_reserve = 1;
/*
* We are no longer going to journal this buffer.
@@ -1246,7 +1248,7 @@ int journal_forget (handle_t *handle, st
spin_unlock(&journal->j_list_lock);
jbd_unlock_bh_state(bh);
__bforget(bh);
- return 0;
+ goto drop;
}
}
} else if (jh->b_transaction) {
@@ -1261,6 +1263,7 @@ int journal_forget (handle_t *handle, st
if (jh->b_next_transaction) {
J_ASSERT(jh->b_next_transaction == transaction);
jh->b_next_transaction = NULL;
+ drop_reserve = 1;
}
}
@@ -1268,6 +1271,11 @@ not_jbd:
spin_unlock(&journal->j_list_lock);
jbd_unlock_bh_state(bh);
__brelse(bh);
+drop:
+ if (drop_reserve) {
+ /* no need to reserve log space for this block -bzzz */
+ handle->h_buffer_credits++;
+ }
return err;
}
_