Re: [PATCH] Linux Raid5/6 abover 2 Terabytes

[Andreas Schwab]

Evan Felix <evan.felix@xxxxxxx> writes:

> Here is a patch that fixes a major issue in the raid5/6 code.  It seems
> that the code:
>
> logical_sector = bi->bi_sector & ~(STRIPE_SECTORS-1);
> (sector_t)     = (sector_t)    & (constant)
>
> that the right side of the & does not get extended correctly when the
> constant is promoted to the sector_t type.  I have CONFIG_LBD turned on
> so sector_t should be 64bits wide.  This fails to properly mask the
> value of 4294967296 (2TB/512) to 4294967296.  in my case it was coming
> out 0.  this cause the loop following this code to read from 0 to
> 4294967296 blocks so it could write one character.
>
> As you might imagine this makes a format of a 3.5TB filesystem take a
> very long time.
>
> Here is the patch:

Alternatively replace ~(STRIPE_SECTORS-1) by -STRIPE_SECTORS, which
doesn't need a cast.

Andreas.

-- 
Andreas Schwab, SuSE Labs, schwab@xxxxxxx
SuSE Linux AG, Maxfeldstraße 5, 90409 Nürnberg, Germany
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