Messages in this thread | | | Date | Sun, 15 Jul 2001 15:36:07 +1200 | From | Chris Wedgwood <> | Subject | Re: [PATCH] 64 bit scsi read/write |
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On Sat, Jul 14, 2001 at 10:11:30PM +0200, Daniel Phillips wrote:
Atomic commit. The superblock, which references the updated version of the filesystem, carries a sequence number and a checksum. It is written to one of two alternating locations. On restart, both locations are read and the highest numbered superblock with a correct checksum is chosen as the new filesystem root.
Yes... and which ever part of the superblock contains the sequence number must be written atomically.
The point is, you _NEED_ to be sure that data written before the superblock (or indeed anywhere further up the tree, you can make changes in theory which don't require super-block updates) are written firmly to the platters before any thing which refers to it is updated.
Alan was saying with IDE you cannot reliably do this, I assume you can with SCSI was my point.
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