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[PATCH] Block Devices support for JFFS2



Hi All,

I have slightly modified JFFS2 to support standard block devices. Now you can
mount a CompactFlash, a hard disk partition, a floppy, or even a loop device
containing a JFFS2 file-system. This allowed me to replace EXT2 on my firewall
which runs on a 16 MB CompactFlash.

BTW, I had to add more checks since the driver had tendency to reformat the block
device when it didn't recognize it :-(. Now, if you mount a block device, you have
to pass "-o format" to mount to force it to erase the unformated blocks. The MTD
behaviour hasn't changed. I tried to do my best to make minimal changes so that
MTD-only users won't notice a change.

Three mounting options have been added :
  -o format (to force erasing of non-formated blocks on a non-MTD block device)
  -o blkdev (to force block device behaviour on and MTD block device. may be
             useful for debugging only, IMHO)
  -o deflate=X : change the compression speed/efficiency when using the deflate
                 method. 0<= X <=9 (just like gzip).

I could save about 5% using -o deflate=9 compared to deflate=3 (which is the default one).
On many actual systems there's no speed loss between 3 and 9 (even my 386sx firewall
supports 9).

Although it seems stable to me (I'm using it in production here), it's a bit too new so
I would recommend everyone to take care. Anyway, I'm very happy with it ; my 16 MB flash
seems so large now :-)

The following patch applies cleanly to kernel 2.4.8-ac7.
You can also get it from: http://wtarreau.free.fr/linux-patches/

Have fun,
Willy Tarreau - http://wtarreau.free.fr/ - mailto:wtarreau@xxxxxxx.fr



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