Re: [RFD] BIO_RW_BARRIER - what it means for devices, filesystems, and dm/md.
From: Stefan Bader
Date: Wed May 30 2007 - 04:55:36 EST
- Next message: Evgeniy Polyakov: "Re: Syslets, Threadlets, generic AIO support, v6"
- Previous message: Ingo Molnar: "Re: Syslets, Threadlets, generic AIO support, v6"
- In reply to: David Chinner: "Re: [RFD] BIO_RW_BARRIER - what it means for devices, filesystems, and dm/md."
- Next in thread: david: "Re: [RFD] BIO_RW_BARRIER - what it means for devices, filesystems,and dm/md."
- Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]
The order that these are expected by the filesystem to hit stable
storage are:
1. block 4 and 10 on stable storage in any order
2. barrier block X on stable storage
3. block 5 and 20 on stable storage in any order
The point I'm trying to make is that in XFS, block 5 and 20 cannot
be allowed to hit the disk before the barrier block because they
have strict order dependency on block X being stable before them,
just like block X has strict order dependency that block 4 and 10
must be stable before we start the barrier block write.
That would be the exactly how I understand Documentation/block/barrier.txt:
"In other words, I/O barrier requests have the following two properties.
1. Request ordering
...
2. Forced flushing to physical medium"
"So, I/O barriers need to guarantee that requests actually get written
to non-volatile medium in order."
Stefan
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
- Next message: Evgeniy Polyakov: "Re: Syslets, Threadlets, generic AIO support, v6"
- Previous message: Ingo Molnar: "Re: Syslets, Threadlets, generic AIO support, v6"
- In reply to: David Chinner: "Re: [RFD] BIO_RW_BARRIER - what it means for devices, filesystems, and dm/md."
- Next in thread: david: "Re: [RFD] BIO_RW_BARRIER - what it means for devices, filesystems,and dm/md."
- Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]