On Sun, 2012-05-27 at 13:33 +0800, Peng Tao wrote:
> Signed-off-by: Peng Tao <tao.peng@xxxxxxx>
> ---
> fs/nfs/blocklayout/blocklayout.c | 20 ++++++++++++++++++++
> 1 files changed, 20 insertions(+), 0 deletions(-)
>
> diff --git a/fs/nfs/blocklayout/blocklayout.c b/fs/nfs/blocklayout/blocklayout.c
> index 53cb450..cdb87a9 100644
> --- a/fs/nfs/blocklayout/blocklayout.c
> +++ b/fs/nfs/blocklayout/blocklayout.c
> @@ -1000,7 +1000,27 @@ static bool bl_dio_begin(struct inode *inode, const struct iovec *iov,
> unsigned long nr_segs, loff_t pos,
> struct blk_plug *plug)
> {
> + unsigned blkmask = NFS_SERVER(inode)->pnfs_blksize - 1;
> + size_t count;
> + int seg;
> + unsigned long addr;
> +
> blk_start_plug(plug);
> +
> + /* Only allow blksized DIO for now.
> + * In theory we can handle page aligned DIO in current block layout
> + * read/write code, but it would require serialization between
> + * concurrent writers and it is far less effecient than just send IO
> + * to MDS.
> + */
> + if (pos & blkmask)
> + return false;
> + for (seg = 0; seg < nr_segs; seg++) {
> + addr = (unsigned long)iov[seg].iov_base;
> + count = iov[seg].iov_len;
> + if (unlikely((addr & blkmask) || (count & blkmask)))
> + return false;
> + }
> return true;
> }
Again, this can and should go in the existing nfs_pageio_ops either in
the pg_init or in the pg_test.
Also, why do you consider it to be direct i/o specific? If the
application is using byte range locking, and the locks aren't page/block
aligned then you are in the same position of having to deal with partial
page writes even in the read/write from page cache situation.
--
Trond Myklebust
Linux NFS client maintainer
NetApp
Trond.Myklebust@xxxxxxxxxx
www.netapp.com
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