[PATCH] ext3: Remove journal_try_start()

journal_try_start() is a function which nonblockingly attempts to open a JBD
transaction handle.  It was added a long time ago when there were concerns
that ext3_writepage() could block kswapd for too long.

It was never clearly necessary.

So the patch throws it all away and just calls the blocking journal_start()
from ext3_writepage().

fs/ext3/inode.c

@@ -1317,9 +1317,6 @@ static int ext3_writepage(struct page *page, struct writeback_control *wbc)
 		goto out_fail;
 
 	needed = ext3_writepage_trans_blocks(inode);
-	if (wbc->for_reclaim)
-		handle = ext3_journal_try_start(inode, needed);
-	else
 	handle = ext3_journal_start(inode, needed);
 				
 	if (IS_ERR(handle)) {

fs/jbd/journal.c

@@ -38,7 +38,6 @@
 #include <linux/proc_fs.h>
 
 EXPORT_SYMBOL(journal_start);
-EXPORT_SYMBOL(journal_try_start);
 EXPORT_SYMBOL(journal_restart);
 EXPORT_SYMBOL(journal_extend);
 EXPORT_SYMBOL(journal_stop);

fs/jbd/transaction.c

@@ -266,113 +266,6 @@ handle_t *journal_start(journal_t *journal, int nblocks)
 	return handle;
 }
 
-/*
- * Return zero on success
- */
-static int try_start_this_handle(journal_t *journal, handle_t *handle)
-{
-	transaction_t *transaction;
-	int needed;
-	int nblocks = handle->h_buffer_credits;
-	int ret = 0;
-
-	jbd_debug(3, "New handle %p maybe going live.\n", handle);
-
-	lock_journal(journal);
-
-	if (is_journal_aborted(journal) ||
-	    (journal->j_errno != 0 && !(journal->j_flags & JFS_ACK_ERR))) {
-		ret = -EROFS;
-		goto fail_unlock;
-	}
-
-	if (journal->j_barrier_count)
-		goto fail_unlock;
-
-	if (!journal->j_running_transaction && get_transaction(journal, 1) == 0)
-		goto fail_unlock;
-	
-	transaction = journal->j_running_transaction;
-	if (transaction->t_state == T_LOCKED)
-		goto fail_unlock;
-	
-	needed = transaction->t_outstanding_credits + nblocks;
-	/* We could run log_start_commit here */
-	if (needed > journal->j_max_transaction_buffers)
-		goto fail_unlock;
-
-	needed = journal->j_max_transaction_buffers;
-	if (journal->j_committing_transaction) 
-		needed += journal->j_committing_transaction->
-						t_outstanding_credits;
-	
-	if (log_space_left(journal) < needed)
-		goto fail_unlock;
-
-	handle->h_transaction = transaction;
-	transaction->t_outstanding_credits += nblocks;
-	transaction->t_updates++;
-	jbd_debug(4, "Handle %p given %d credits (total %d, free %d)\n",
-		  handle, nblocks, transaction->t_outstanding_credits,
-		  log_space_left(journal));
-	unlock_journal(journal);
-	return 0;
-
-fail_unlock:
-	unlock_journal(journal);
-	if (ret >= 0)
-		ret = -1;
-	return ret;
-}
-
-/**
- * handle_t *journal_try_start() - Don't block, but try and get a handle
- * @journal: Journal to start transaction on.
- * @nblocks: number of block buffer we might modify
- * 
- * Try to start a handle, but non-blockingly.  If we weren't able
- * to, return an ERR_PTR value.
- */
-handle_t *journal_try_start(journal_t *journal, int nblocks)
-{
-	handle_t *handle = journal_current_handle();
-	int err;
-	
-	if (!journal)
-		return ERR_PTR(-EROFS);
-
-	if (handle) {
-		jbd_debug(4, "h_ref %d -> %d\n",
-				handle->h_ref,
-				handle->h_ref + 1);
-		J_ASSERT(handle->h_transaction->t_journal == journal);
-		if (is_handle_aborted(handle))
-			return ERR_PTR(-EIO);
-		handle->h_ref++;
-		return handle;
-	} else {
-		jbd_debug(4, "no current transaction\n");
-	}
-	
-	if (is_journal_aborted(journal))
-		return ERR_PTR(-EIO);
-
-	handle = new_handle(nblocks);
-	if (!handle)
-		return ERR_PTR(-ENOMEM);
-
-	current->journal_info = handle;
-
-	err = try_start_this_handle(journal, handle);
-	if (err < 0) {
-		kfree(handle);
-		current->journal_info = NULL;
-		return ERR_PTR(err);
-	}
-
-	return handle;
-}
-
 /**
  * int journal_extend() - extend buffer credits.
  * @handle:  handle to 'extend'
@@ -1726,13 +1619,6 @@ static inline int __journal_try_to_free_buffer(struct buffer_head *bh)
  * to be called. We do this if the page is releasable by try_to_free_buffers().
  * We also do it if the page has locked or dirty buffers and the caller wants
  * us to perform sync or async writeout.
- */
-int journal_try_to_free_buffers(journal_t *journal, 
-				struct page *page, int unused_gfp_mask)
-{
-/*
- * journal_try_to_free_buffers().  Try to remove all this page's buffers
- * from the journal.
  *
  * This complicates JBD locking somewhat.  We aren't protected by the
  * BKL here.  We wish to remove the buffer from its committing or
@@ -1752,6 +1638,9 @@ int journal_try_to_free_buffers(journal_t *journal,
  * cannot happen because we never reallocate freed data as metadata
  * while the data is part of a transaction.  Yes?
  */
+int journal_try_to_free_buffers(journal_t *journal, 
+				struct page *page, int unused_gfp_mask)
+{
 	struct buffer_head *head;
 	struct buffer_head *bh;
 	int ret = 0;

include/linux/ext3_jbd.h

@@ -210,14 +210,6 @@ static inline handle_t *ext3_journal_start(struct inode *inode, int nblocks)
 	return journal_start(journal, nblocks);
 }
 
-static inline handle_t *
-ext3_journal_try_start(struct inode *inode, int nblocks)
-{
-	if (inode->i_sb->s_flags & MS_RDONLY)
-		return ERR_PTR(-EROFS);
-	return journal_try_start(EXT3_JOURNAL(inode), nblocks);
-}
-
 /* 
  * The only special thing we need to do here is to make sure that all
  * journal_stop calls result in the superblock being marked dirty, so

include/linux/jbd.h

@@ -726,7 +726,6 @@ static inline handle_t *journal_current_handle(void)
  */
 
 extern handle_t *journal_start(journal_t *, int nblocks);
-extern handle_t *journal_try_start(journal_t *, int nblocks);
 extern int	 journal_restart (handle_t *, int nblocks);
 extern int	 journal_extend (handle_t *, int nblocks);
 extern int	 journal_get_write_access (handle_t *, struct buffer_head *);