[Patch 4/7] 2.4.20-pre4/ext3: Sanity check for Intermezzo/ext3 interactions

[Stephen Tweedie]

Nowhere in journal_start() (or more specifically in start_this_handle()
is any sanity checking on the number of blocks requested for a single
handle done.  If you request more than journal_size/4 blocks for a handle
it will loop endlessly on repeat_locked: trying to "free" enough blocks
to satisfy the request.  The below patch validates the number of blocks
requested is small enough to actually be allocated, otherwise returns
-ENOSPC.

--- linux-2.4-ext3merge/fs/jbd/transaction.c.=K0003=.orig	Thu Sep 26 12:25:37 2002
+++ linux-2.4-ext3merge/fs/jbd/transaction.c	Thu Sep 26 12:25:37 2002
@@ -90,7 +90,14 @@
 	transaction_t *transaction;
 	int needed;
 	int nblocks = handle->h_buffer_credits;
-	
+
+	if (nblocks > journal->j_max_transaction_buffers) {
+		jbd_debug(1, "JBD: %s wants too many credits (%d > %d)\n",
+		       current->comm, nblocks,
+		       journal->j_max_transaction_buffers);
+		return -ENOSPC;
+	}
+
 	jbd_debug(3, "New handle %p going live.\n", handle);
 
 repeat: