Hi All Here is a question to be confirmed. In ext3_ioctl() with "cmd == EXT3_IOC_SETFLAGS", we firstly lock "inode->i_mutex", start a handle with 1 journal-block by calling ext3_journal_start(). In ext3_new_blocks(), say QUOTA was enabled with vfsv0 format, we will call the function "DQUOT_ALLOC_BLOCK()". The handle in ext3_new_blocks() was started by high-level functions, and DQUOT_ALLOC_BLOCK() will finally calles ext3_quota_write() in which it try to lock the "i_mutex" of the inode of a quota-file. At it happens, when we want to modify the inodes of quota-files via ext3_ioctl(cmd = EXT3_IOC_SETFLAGS) (say process-A), another guy try to execute ext3_quota_write() by calling DQUOT_ALLOC_BLOCK() (say process-B). I guess a potential deadlock between process-A and process-B would happen in such a executing sequence: (1) process-B got many journal-blocks, then came into ext3_new_blocks(), hung up (2) process-A locked i_mutex of the inode of a quota-file, then try to starts a handle. Unfortunately, there are no enough journal-blocks left for process-A. (3) process-B awakened, and came into DQUOT_ALLOC_BLOCK(), finally came into the function ext3_quota_write() who also wants to lock the i_mutex of the inode of a quota-file. But the i_mutex was locked by process-A. so process-B has no choice but to wait. (4) if the ext3-filesystem was too busy to release jounal-blocks for process-A, or a unexpected incident happened. Both the two situations would result in no journal-blocks for any other processes. Apparently, process-A have to wait for available journal-blocks. so process-A was hung-up with i_mutex of the inode of a quota-file locked. (5) process-B was blocked by the "inode->i_mutex" subsequently. a deadlock happened? is such a suppose reasonable? Payphone - To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
