Hi, I have a doubt in the ordering of writes in ext3. Any help is appreciated. Ext3 enforces certain ordering in writes to ensure data integrity. For example, the journal writes are issued first and only after their successful completion the actual writes are issued. Sometimes we need to maintain ordering across transactions also. This is needed because if the actual writes of one transaction and the journal writes of another transaction are scheduled differently then data integrity may be lost. For example, assume we have two transactions T1 and T2 modifying block b1 and b2 of a file respectively. (1) T1: Modify block b1. (2) T1: Issue the journal write for block b1. (3) T1: Issue the actual write to block b1. (4) T2: Modify block b2. (5) T2: Issue the journal write for block b2. (6) T2: Issue the actual write to block b2. Now, notice that if the file system is not enforcing ordering across transactions, then writes (3) and (5) may get reordered by the disk scheduler (which doesn't know about journaling) such that (5) happens first and then (3) happens. In such a case, if the system crashes after writing the journal block for b2 in transaction T2 but before updating the actual block b1 of transaction T1, then the system will lose its data integrity. Will this situation ever occur in ext3 ? thanks, Vijayan _______________________________________________ Ext3-users@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/ext3-users
