Review Request: kio-file: sync file copy to /media/

[Davide Bettio]

> On 2010-01-22 20:41:51, Andras Mantia wrote:
> > Did you profile the copying speed? Are you sure it will not wear out too quickly the USB media? Maybe O_SYNC is better than using full sync mount, but I'd not introduce the change without profiling and testing (a lot) on USB memories.
> 
> Davide Bettio wrote:
>     Next week I will have more free time so I can do some benchmarks. It shouldn't damage flash drives but anyway I will look for more information about that.
>     
>
> 
> Davide Bettio wrote:
>     http://www.westnet.com/~gsmith/content/postgresql/TuningPGWAL.htm
>     Do you think that O_DSYNC might be better?
> 
> David Faure wrote:
>     From man 2 open:
>     
>     POSIX provides for three different variants of synchronized I/O, corresponding to the flags  O_SYNC, O_DSYNC and O_RSYNC. Currently (2.1.130) these are all synonymous under Linux.
> 
> Davide Bettio wrote:
>     The situation might have changed in the meantime (2.1.130 is really old).
>     Anyway the point is if fileSize / MAX_IPC_SIZE updates to the same block (the one which contain the filesize) are acceptable. According to manufacturers flash memories can be written up to 100,000 - 1,000,000 times. Anyway it seems that FAT has no filesize attribute so it will not be an issue on that filesystem.

is it possible to preallocate all the space required by the file which is going to be written without spending time writing zeroes?


- Davide


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On 2010-01-22 20:42:25, Davide Bettio wrote:
> 
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> 
> (Updated 2010-01-22 20:42:25)
> 
> 
> Review request for kdelibs, Kevin Ottens and David Faure.
> 
> 
> Summary
> -------
> 
> This simple patch allows file copy to external devices to be synchronous. This patch assumes that external devices are mounted on a subdirectory of /media/. If /media/ is not used this patch will not work so everything will be as before.
> For more dettails see also https://bugs.kde.org/show_bug.cgi?id=195044.
> 
> 
> Diffs
> -----
> 
>   /trunk/KDE/kdelibs/kioslave/file/file_unix.cpp 1077183 
> 
> Diff: http://reviewboard.kde.org/r/2690/diff
> 
> 
> Testing
> -------
> 
> This patch is recent, so I'm testing it right now. kio-file is a critical component so I will do more tests.
> 
> Checking for file corruption might be a good idea:
> dd if=/dev/full of=testFile count=numOfBlocks
> md5sum testFile
> Copy it, umount, mount and check the md5sum.
> 
> 
> Thanks,
> 
> Davide
> 
>