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SubjectRe: [PATCH 7/8] dm: __LOW macro fix no. 2
On Wed, Feb 26, 2003 at 05:12:49PM +0000, Joe Thornber wrote:
> Another fix for the __LOW macro.
> When dm_table and dm_target structures are initialized, the "limits" fields
> (struct io_restrictions) are initialized to zero (e.g. in dm_table_add_target()
> in dm-table.c). However, zero is not a useable value in these fields. The
> request queue will never let an I/O through, regardless of how small it might
> be, if max_sectors is set to zero (see generic_make_request in ll_rw_blk.c).
> This change to the __LOW() macro sets these fields correctly when they are
> first initialized. [Kevin Corry]
> --- diff/drivers/md/dm-table.c 2003-02-26 16:10:02.000000000 +0000
> +++ source/drivers/md/dm-table.c 2003-02-26 16:10:19.000000000 +0000
> @@ -79,7 +79,7 @@
> }
> #define __HIGH(l, r) if (*(l) < (r)) *(l) = (r)
> -#define __LOW(l, r) if (*(l) > (r)) *(l) = (r)
> +#define __LOW(l, r) if (*(l) == 0 || *(l) > (r)) *(l) = (r)

Any reason to not use the existing min() and max() macros instead of
these? Then:
__HIGH(foo, bar);
can be written as:
foo = max(foo, bar);
which is (IMHO) easier to read.

By special casing the logic in your __LOW() macro, you're only asking
for trouble in the long run :)


greg k-h
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