On Fri, Jun 08, 2012 at 03:38:26PM +1000, Dave Chinner wrote: > From: Dave Chinner <dchinner@xxxxxxxxxx> > > To support discontiguous buffers in the buffer cache, we need to > separate the cache index variables from the I/O map. While this is > currently a 1:1 mapping, discontiguous buffer support will break > this relationship. > > However, for caching purposes, we can still treat them the same as a > contiguous buffer - the block number of the first block and the > length of the buffer - as that is still a unique representation. > Also, the only way we will ever access the discontiguous regions of > buffers is via bulding the complete buffer in the first place, so > using the initial block number and entire buffer length is a sane > way to index the buffers. > > Add a block mapping vector construct to the xfs_buf and use it in > the places where we are doing IO instead of the current > b_bn/b_length variables. > > Signed-off-by: Dave Chinner <dchinner@xxxxxxxxxx> > --- > fs/xfs/xfs_buf.c | 21 ++++++++++++--------- > fs/xfs/xfs_buf.h | 17 +++++++++++++---- > 2 files changed, 25 insertions(+), 13 deletions(-) > > diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c > index a4beb42..90c5b6a 100644 > --- a/fs/xfs/xfs_buf.c > +++ b/fs/xfs/xfs_buf.c > @@ -199,9 +199,11 @@ xfs_buf_alloc( > * most cases but may be reset (e.g. XFS recovery). > */ > bp->b_length = numblks; > + bp->b_map.bm_len = numblks; > bp->b_io_length = numblks; > bp->b_flags = flags; > bp->b_bn = blkno; > + bp->b_map.bm_bn = blkno; nipick: any reason not to initialize the two fields of b_map next to each other? > - bp->b_io_length = bp->b_length; > - oh, I just mentioned that we can remove this in reply to Jan's patch, so this is already taken care of, too. > #ifdef XFS_BUF_LOCK_TRACKING > int b_last_holder; > #endif > @@ -233,8 +242,8 @@ void xfs_buf_stale(struct xfs_buf *bp); > #define XFS_BUF_UNWRITE(bp) ((bp)->b_flags &= ~XBF_WRITE) > #define XFS_BUF_ISWRITE(bp) ((bp)->b_flags & XBF_WRITE) > > -#define XFS_BUF_ADDR(bp) ((bp)->b_bn) > -#define XFS_BUF_SET_ADDR(bp, bno) ((bp)->b_bn = (xfs_daddr_t)(bno)) > +#define XFS_BUF_ADDR(bp) ((bp)->b_map.bm_bn) > +#define XFS_BUF_SET_ADDR(bp, bno) ((bp)->b_map.bm_bn = (xfs_daddr_t)(bno)) It's not really obvious why XFS_BUF_SET_ADDR should not set b_bn from it's defintion. Looking at the callers it seems because it's only used for uncached buffers, which never use b_bn, but it's still confusing. I'm fine with keeping it for now bith a big comment to get this series in, but XFS_BUF_SET_ADDR and b_io_length probably should go away ASAP in favor or a variant of xfs_buf_iorequest that takes a bn/len pair . _______________________________________________ xfs mailing list xfs@xxxxxxxxxxx http://oss.sgi.com/mailman/listinfo/xfs
