[PATCH] reiserfs: handle cnode allocation failure gracefully

If an external device is used for a journal, by default it will use the
entire device.  The reiserfs journal code allocates structures per journal
block when it mounts the file system.  If the journal device is too large,
and memory cannot be allocated for the structures, it will continue and
ultimately panic when it can't pull one off the free list.

This patch handles the allocation failure gracefully and prints an error
message at mount time.

Changes: Updated error message to be more descriptive to the user.

Discussed and approved on ReiserFS Mailing List, Nov 28.
Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

fs/reiserfs/journal.c

@@ -2757,6 +2757,15 @@ int journal_init(struct super_block *p_s_sb, const char *j_dev_name,
 	journal->j_cnode_used = 0;
 	journal->j_must_wait = 0;
 
+	if (journal->j_cnode_free == 0) {
+        	reiserfs_warning(p_s_sb, "journal-2004: Journal cnode memory "
+		                 "allocation failed (%ld bytes). Journal is "
+		                 "too large for available memory. Usually "
+		                 "this is due to a journal that is too large.",
+		                 sizeof (struct reiserfs_journal_cnode) * num_cnodes);
+        	goto free_and_return;
+	}
+
 	init_journal_hash(p_s_sb);
 	jl = journal->j_current_jl;
 	jl->j_list_bitmap = get_list_bitmap(p_s_sb, jl);