Re: [PATCH 5/5] block: enable dax for raw block devices

From: Dave Chinner
Date: Sun Oct 25 2015 - 17:23:24 EST

On Thu, Oct 22, 2015 at 11:08:18PM +0200, Jan Kara wrote:
> Ugh2: Now I realized that DAX mmap isn't safe wrt fs freezing even for
> filesystems since there's nothing which writeprotects pages that are
> writeably mapped. In normal path, page writeback does this but that doesn't
> happen for DAX. I remember we once talked about this but it got lost.
> We need something like walk all filesystem inodes during fs freeze and
> writeprotect all pages that are mapped. But that's going to be slow...

fsync() has the same problem - we have no record of the pages that
need to be committed and then write protected when fsync() is called
after write()...


Dave Chinner
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at
Please read the FAQ at