On 2011-07-12 22:29, Trond Myklebust wrote:
> If an attempt to do pNFS fails, and we have to fall back to writing through
> the MDS, then we may want to re-coalesce the requests that we already have
> since the block size for the MDS read/writes may be different to that of
> the DS read/writes.
>
> Signed-off-by: Trond Myklebust <Trond.Myklebust@xxxxxxxxxx>
> ---
> fs/nfs/pagelist.c | 57 +++++++++++++++++++++++++++++++++++++++++++--
> include/linux/nfs_page.h | 3 +-
> 2 files changed, 56 insertions(+), 4 deletions(-)
>
> diff --git a/fs/nfs/pagelist.c b/fs/nfs/pagelist.c
> index d421e19..7139dbf 100644
> --- a/fs/nfs/pagelist.c
> +++ b/fs/nfs/pagelist.c
> @@ -240,6 +240,7 @@ void nfs_pageio_init(struct nfs_pageio_descriptor *desc,
> desc->pg_bsize = bsize;
> desc->pg_base = 0;
> desc->pg_moreio = 0;
> + desc->pg_recoalesce = 0;
> desc->pg_inode = inode;
> desc->pg_ops = pg_ops;
> desc->pg_ioflags = io_flags;
> @@ -331,7 +332,7 @@ static void nfs_pageio_doio(struct nfs_pageio_descriptor *desc)
> * Returns true if the request 'req' was successfully coalesced into the
> * existing list of pages 'desc'.
> */
> -int nfs_pageio_add_request(struct nfs_pageio_descriptor *desc,
> +static int __nfs_pageio_add_request(struct nfs_pageio_descriptor *desc,
> struct nfs_page *req)
> {
> while (!nfs_pageio_do_add_request(desc, req)) {
> @@ -340,17 +341,67 @@ int nfs_pageio_add_request(struct nfs_pageio_descriptor *desc,
> if (desc->pg_error < 0)
> return 0;
> desc->pg_moreio = 0;
> + if (desc->pg_recoalesce)
> + return 0;
> }
> return 1;
> }
>
> +static int nfs_do_recoalesce(struct nfs_pageio_descriptor *desc)
> +{
> + LIST_HEAD(head);
> +
> + do {
> + list_splice_init(&desc->pg_list, &head);
> + desc->pg_bytes_written -= desc->pg_count;
> + desc->pg_count = 0;
> + desc->pg_base = 0;
> + desc->pg_recoalesce = 0;
> +
> + while (!list_empty(&head)) {
> + struct nfs_page *req;
> +
> + req = list_first_entry(&head, struct nfs_page, wb_list);
> + nfs_list_remove_request(req);
> + if (__nfs_pageio_add_request(desc, req))
> + continue;
> + if (desc->pg_error < 0)
> + return 0;
> + break;
> + }
> + } while (desc->pg_recoalesce);
> + return 1;
> +}
> +
> +int nfs_pageio_add_request(struct nfs_pageio_descriptor *desc,
> + struct nfs_page *req)
> +{
> + int ret;
> +
> + do {
> + ret = __nfs_pageio_add_request(desc, req);
> + if (ret)
> + break;
> + if (desc->pg_error < 0)
> + break;
> + ret = nfs_do_recoalesce(desc);
> + } while (ret);
> + return ret;
> +}
> +
> /**
> * nfs_pageio_complete - Complete I/O on an nfs_pageio_descriptor
> * @desc: pointer to io descriptor
> */
> void nfs_pageio_complete(struct nfs_pageio_descriptor *desc)
> {
> - nfs_pageio_doio(desc);
> + for (;;) {
> + nfs_pageio_doio(desc);
> + if (!desc->pg_recoalesce)
> + break;
> + if (!nfs_do_recoalesce(desc))
> + break;
> + }
nit: how about the following?
do
nfs_pageio_doio(desc);
while (desc->pg_recoalesce && nfs_do_recoalesce(desc));
Benny
> }
>
> /**
> @@ -369,7 +420,7 @@ void nfs_pageio_cond_complete(struct nfs_pageio_descriptor *desc, pgoff_t index)
> if (!list_empty(&desc->pg_list)) {
> struct nfs_page *prev = nfs_list_entry(desc->pg_list.prev);
> if (index != prev->wb_index + 1)
> - nfs_pageio_doio(desc);
> + nfs_pageio_complete(desc);
> }
> }
>
> diff --git a/include/linux/nfs_page.h b/include/linux/nfs_page.h
> index db3194f..7241b2a 100644
> --- a/include/linux/nfs_page.h
> +++ b/include/linux/nfs_page.h
> @@ -68,7 +68,8 @@ struct nfs_pageio_descriptor {
> size_t pg_count;
> size_t pg_bsize;
> unsigned int pg_base;
> - char pg_moreio;
> + unsigned char pg_moreio : 1,
> + pg_recoalesce : 1;
>
> struct inode *pg_inode;
> const struct nfs_pageio_ops *pg_ops;
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