On 6/5/14, 9:53 PM, Eric Sandeen wrote: > On 6/5/14, 8:42 PM, Dave Chinner wrote: >> On Thu, Jun 05, 2014 at 07:00:02PM -0500, Eric Sandeen wrote: >>> On 6/5/14, 6:56 PM, Dave Chinner wrote: >>>> On Thu, Jun 05, 2014 at 06:09:16PM -0500, Eric Sandeen wrote: >>> >>> ... >>> >>>>> But ... should we maybe just do this once and for all in >>>>> xfs_sb_from_disk? I'm not sure leaving it up to every >>>>> caller is a good idea, unless somebody ahs a reason to >>>>> pre-populate some fields - I can't imagine why that would >>>>> be, though... >>>> >>>> We don't ever read in the CRC field into the in-memory structures >>>> because it has no meaning in memory. Simiarly, we don't ever write >>>> the CRC field from the in-core structure because we always >>>> re-calculate it in the IO path if CRCs are configured. That is >>>> consistent behaviour across the entire code-base. But as you say in userspace, this libxfs_sb_to_disk(buf, sbp, XFS_SB_ALL_BITS) *does* write it. kernelspace does the same here: 0 xfs_fsops.c xfs_growfs_data_private 520 xfs_sb_to_disk(XFS_BUF_TO_SBP(bp), &mp->m_sb, XFS_SB_ALL_BITS); >>> <snip stuff> >>> >>>> Perhaps we should move the memset() to within xfs_sb_from_disk() >>>> to make this explicit? >>> >>> Yes, that's what I meant by "this" in "do this once and for all" - >>> sorry, that wasn't clear. memset(0) in xfs_sb_from_disk(). >> >> I didn't read it clearly. my fault. >> >>> Yeah, the more I think about it, the more I think that's probably >>> the obviously correct thing to do. > > Actually, a memset() seems like overkill - every field except > sb_crc is explicitly filled in in the function. > > Maybe better to just set sb_crc to 0, with a comment as to why? > I think I'll whip that one up. But now I realize we do sometimes write the in-memory value to disk, as seen above. Backing up - shouldn't we just go ahead and read/write it from/to disk just like every other field, at least in the cases where we are writing all, and when we are reading (which always reads all)? -Eric _______________________________________________ xfs mailing list xfs@xxxxxxxxxxx http://oss.sgi.com/mailman/listinfo/xfs
