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SubjectRe: [Fdutils] DMA cache consistency bug introduced in 2.6.28
Linus Torvalds wrote:

> diff --git a/drivers/block/floppy.c b/drivers/block/floppy.c
> index 3266b4f..9c9148c 100644
> --- a/drivers/block/floppy.c
> +++ b/drivers/block/floppy.c
> @@ -2237,13 +2237,10 @@ static void setup_format_params(int track)
> for (count = 1; count <= F_SECT_PER_TRACK; ++count) {
> here[n].sect = count;
> n = (n + il) % F_SECT_PER_TRACK;
> - if (here[n].sect) { /* sector busy, find next free sector */
> + while (here[n].sect) { /* sector busy, find next free sector */
> ++n;
> - if (n >= F_SECT_PER_TRACK) {
> + if (n >= F_SECT_PER_TRACK)
> n -= F_SECT_PER_TRACK;
> - while (here[n].sect)
> - ++n;
> - }
> }
> }
> if (_floppy->stretch & FD_SECTBASEMASK) {

The original code does indeed look a little bit strange... and might
break if there is a long run of "busy" sectors near the end of the
physical track. Or maybe there is a mathematical reason why this
situation cannot occur. I'll have to think about it a little bit more to
come up with a test case that will break either the new or old code.

But in any case, if a bug would occur due to this code, it would only
depend on the format's parameters, and not on the hardwarde.

Regards,

Alain


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