Re: [RFC] FIEMAP and disk sync issues

[Vladimir 'φ-coder/phcoder' Serbinenko]

On 27.01.2012 20:04, Phillip Susi wrote:
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> On 1/27/2012 8:28 AM, Vladimir 'φ-coder/phcoder' Serbinenko wrote:
> > Hello, all. When someone installs using blocklists (discouraged
> > and unreliable), we use GRUB internal fs reader in order to
> > determine core.img blocklists. With Linux we call fsync and an
> > ioctl on partition in order to flush the cache. I also tried adding
> > "sync" which didn't make any difference. Unfortunately it doesn't
> > seem to be good enough on
> By "sync" you mean running the sync command?
Actually the sync () call
>   If so, that absolutely,
> positively should flush everything to disk.  If it isn't then there's
> a major kernel bug.  An fsync() on the core.img file ( not the
> partition device ) also should flush everything needed to find that
> file, without flushing everything else that isn't.
I'll recheck. But considering that I ran into some data loss it's 
possible that I have some kind of hardware or software failure (most 
likely because of new kernel and xen tests). Busy now doing the backups 
in case it gets worse
> Doing an fsync() on the partition device will flush buffers from a
> process directly opening the block dev and performing IO there, not
> the buffers for files within the filesystem on that block device.
> IIRC, ext2 uses the block buffers for directory access so that
> partition fsync will flush directories, but ext3 and ext4 do not.
>
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--
Regards
Vladimir 'φ-coder/phcoder' Serbinenko