Subject: Re: CVS commit: src/sys/miscfs/genfs
To: None <firstname.lastname@example.org>
From: YAMAMOTO Takashi <email@example.com>
Date: 11/30/2005 11:37:06
> > > Learn genfs that (struct buf *)->b_lblkno allways need to point to the
> > > logical block number of the file instead of allways zero.
> > for what is it necessary?
> buffers passed from bread()/bwrite() have this field set up correctly
> whereas genfs just bluntly sets it to zero.
the current convention for VOP_STRATEGY is
- do BMAP by itself if b_lblkno == b_blkno.
- otherwise use b_blkno.
so i don't think there is a problem with setting it to zero.
> Note that there are other problems currently with buffer passing to
> strategy, see my PR # "kern/32193: vop_strategy gets broken struct buf's
> passed by genfs/bread, possible memory leakage"
i replied to the PR.
> For filingsystems that rely/want to do 1:1 mapping in bmap, its a PITA that
> suddenly the b_lblknr gets cleared and in one routine they have to manually
> correct this.
"1:1 mapping" means "always lblkno == blkno" like nfs?
why can't you follow what nfs does?