On Dec 07, 2007 09:52 -0600, Jose R. Santos wrote:
> Andreas Dilger <adilger@xxxxxxx> wrote:
> > There is no particular reason that this ratio needs to be "*100", it could
> > just as easily be a fraction of 256 and make the multiply into a shift.
> > The free_block_ratio would be 26 in that case.
>
> The idea here is to reserve 10% (free_block_ratio) of free blocks in a
> flexbg for allocation of new files and expansion of existing one. The
> "*100" make the math here easy but this still something that need to be
> tune further. I'm sure we can do this in a series of shifts, just
> haven't spent the time thinking of a clever way to do this.
This is a common misconception for code to have 10% mean 10 / 100. It
is just as good to have 26/256
> > > @@ -622,7 +631,9 @@ struct ext4_super_block {
> > > __le16 s_mmp_interval; /* # seconds to wait in MMP checking */
> > > __le64 s_mmp_block; /* Block for multi-mount protection */
> > > __le32 s_raid_stripe_width; /* blocks on all data disks (N*stride)*/
> > > - __u32 s_reserved[163]; /* Padding to the end of the block */
> > > + __le16 s_flex_bg_size; /* FLEX_BG group size */
> >
> > Shouldn't this be "s_flex_bg_bits"?
>
> I debated whether to store this as the s_flex_bg_size and calculate the
> bits during the filesystem mount time or just stored the bit in the
> super block to begging with. The reason I stored the size is that it
> seemed more in line with the other fields in the super block. I don't
> mind either way since this is more of a style issue, although saving an
> extra 8bits in the super block may be good enough reason to change it.
I'd think being able to avoid the divide for every inode allocation is more
important than 8 bits in the superblock.
> > My preference would be to have "if (EXT2_HAS_INCOMPAT...) { ... } else {"
> > (i.e. add { } for the first part) since there are { } on the second part,
> > and it is just easier to read.
>
> Mine too, but checkpatch complained about this. :)
Time to fix checkpatch it would seem.
Cheers, Andreas
--
Andreas Dilger
Sr. Staff Engineer, Lustre Group
Sun Microsystems of Canada, Inc.
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