On Sun, 17 Jan 2010 10:19:30 -0600, Eric Sandeen <sandeen@xxxxxxxxxx> wrote:
> Aneesh Kumar K. V wrote:
>
> > How about
> >
> > EXT4_GET_BLOCKS_CREATE. Indicate we should do block
> > allocation. But that flag alone doesn't say whether we are suppose
> > to create init or uninit extent.
> >
> > EXT4_GET_BLOCKS_UNINIT_EXT -> Request the creation of uninit extent
> >
> > EXT4_GET_BLOCKS_CREATE_UNINIT_EXT -> EXT4_GET_BLOCKS_CREATE|EXT4_GET_BLOCKS_UNINIT_EXT;
> >
> > EXT4_GET_BLOCKS_DELALLOC_RESERVE -> Request for delayed allocaion
> > reservation
> >
> > EXT4_GET_BLOCKS_PRE_IO -> 0x0008 -> Indicate that we should do all
> > necessary extent split and make the requested range in to single extent.
> >
> > EXT4_GET_BLOCKS_CONVERT_IO -> Convert the specified range which should be a
> > single extent into init and then try to merge the extent to left/right
> >
> > EXT4_GET_BLOCKS_IO_CREATE_EXT -> EXT4_GET_BLOCKS_PRE_IO | EXT4_GET_BLOCKS_CREATE_UNINIT_EXT
> >
> > EXT4_GET_BLOCKS_IO_CONVERT_EXT -> EXT4_GET_BLOCKS_CREATE | EXT4_GET_BLOCKS_CONVERT_IO;
>
>
> In addition to Aneesh's suggestions, I'm not sure of the value of
> creating more
>
> #define FLAG_A = FLAG_B|FLAG_C
>
> flag macros; unless you have this all in your head you just have to
> go look up the flag definition anyway, since we usually test individual
> flags not the aggregates. I'm wondering if it might be better to just
> explicitly send in the OR'd flags rather than creating a new one, to
> see the code flow better.
>
> Maybe it saves space, but at the cost of easy understanding IMHO.
> At least that's been my experience.
It help us to do things like below
if (flag & FLAG_B)
/* we need to do things for flag B */
if (flag & FLAG_C)
/* things for flag C */
instead of
if ((flag & FLAG_A) || (flag & FLAG_D)
/* things related to previous flag B */
So it simplifies the if condition.
-aneesh
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