Many years ago it was the case that a
while (1) {
write(fd, buf, 1);
lseek(fd, 0, SEEK_SET);
}
would livelock kjournald because kjournald could never clean all the buffers
on the transaction's list.
So I put some code in journal_dirty_data() to detect this and to block the
write() caller. It can cause unpleasant latencies under some circumstances.
With the dual list writeout arrangement in journal_commit_transaction() the
livelock is no longer possible so we can remove this code.
Signed-off-by: Andrew Morton <akpm@osdl.org>
---
25-akpm/fs/jbd/transaction.c | 23 -----------------------
1 files changed, 23 deletions(-)
diff -puN fs/jbd/transaction.c~jbd-remove-livelock-avoidance fs/jbd/transaction.c
--- 25/fs/jbd/transaction.c~jbd-remove-livelock-avoidance 2004-07-02 15:51:16.348017120 -0700
+++ 25-akpm/fs/jbd/transaction.c 2004-07-02 15:51:16.358015600 -0700
@@ -940,7 +940,6 @@ out:
int journal_dirty_data(handle_t *handle, struct buffer_head *bh)
{
journal_t *journal = handle->h_transaction->t_journal;
- int need_brelse = 0;
struct journal_head *jh;
if (is_handle_aborted(handle))
@@ -1025,24 +1024,6 @@ int journal_dirty_data(handle_t *handle,
goto no_journal;
}
- /*
- * This buffer may be undergoing writeout in commit. We
- * can't return from here and let the caller dirty it
- * again because that can cause the write-out loop in
- * commit to never terminate.
- */
- if (buffer_dirty(bh)) {
- get_bh(bh);
- spin_unlock(&journal->j_list_lock);
- jbd_unlock_bh_state(bh);
- need_brelse = 1;
- sync_dirty_buffer(bh);
- jbd_lock_bh_state(bh);
- spin_lock(&journal->j_list_lock);
- /* The buffer may become locked again at any
- time if it is redirtied */
- }
-
/* journal_clean_data_list() may have got there first */
if (jh->b_transaction != NULL) {
JBUFFER_TRACE(jh, "unfile from commit");
@@ -1072,10 +1053,6 @@ int journal_dirty_data(handle_t *handle,
no_journal:
spin_unlock(&journal->j_list_lock);
jbd_unlock_bh_state(bh);
- if (need_brelse) {
- BUFFER_TRACE(bh, "brelse");
- __brelse(bh);
- }
JBUFFER_TRACE(jh, "exit");
journal_put_journal_head(jh);
return 0;
_