NFS: Read pages from FS-Cache into an NFS inode

Read pages from an FS-Cache data storage object representing an inode into an
NFS inode.

Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Steve Dickson <steved@redhat.com>
Acked-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Acked-by: Al Viro <viro@zeniv.linux.org.uk>
Tested-by: Daire Byrne <Daire.Byrne@framestore.com>

1 files changed, 112 insertions, 0 deletions

diff --git a/fs/nfs/fscache.c b/fs/nfs/fscache.c
index f673d35d8b89..3a3056657858 100644
--- a/fs/nfs/fscache.c
+++ b/fs/nfs/fscache.c
@@ -381,3 +381,115 @@ void __nfs_fscache_invalidate_page(struct page *page, struct inode *inode)
         nfs_add_fscache_stats(page->mapping->host,
                               NFSIOS_FSCACHE_PAGES_UNCACHED, 1);
 }
+
+/*
+ * Handle completion of a page being read from the cache.
+ * - Called in process (keventd) context.
+ */
+static void nfs_readpage_from_fscache_complete(struct page *page,
+                                               void *context,
+                                               int error)
+{
+        dfprintk(FSCACHE,
+                 "NFS: readpage_from_fscache_complete (0x%p/0x%p/%d)\n",
+                 page, context, error);
+
+        /* if the read completes with an error, we just unlock the page and let
+         * the VM reissue the readpage */
+        if (!error) {
+                SetPageUptodate(page);
+                unlock_page(page);
+        } else {
+                error = nfs_readpage_async(context, page->mapping->host, page);
+                if (error)
+                        unlock_page(page);
+        }
+}
+
+/*
+ * Retrieve a page from fscache
+ */
+int __nfs_readpage_from_fscache(struct nfs_open_context *ctx,
+                                struct inode *inode, struct page *page)
+{
+        int ret;
+
+        dfprintk(FSCACHE,
+                 "NFS: readpage_from_fscache(fsc:%p/p:%p(i:%lx f:%lx)/0x%p)\n",
+                 NFS_I(inode)->fscache, page, page->index, page->flags, inode);
+
+        ret = fscache_read_or_alloc_page(NFS_I(inode)->fscache,
+                                         page,
+                                         nfs_readpage_from_fscache_complete,
+                                         ctx,
+                                         GFP_KERNEL);
+
+        switch (ret) {
+        case 0: /* read BIO submitted (page in fscache) */
+                dfprintk(FSCACHE,
+                         "NFS:    readpage_from_fscache: BIO submitted\n");
+                nfs_add_fscache_stats(inode, NFSIOS_FSCACHE_PAGES_READ_OK, 1);
+                return ret;
+
+        case -ENOBUFS: /* inode not in cache */
+        case -ENODATA: /* page not in cache */
+                nfs_add_fscache_stats(inode, NFSIOS_FSCACHE_PAGES_READ_FAIL, 1);
+                dfprintk(FSCACHE,
+                         "NFS:    readpage_from_fscache %d\n", ret);
+                return 1;
+
+        default:
+                dfprintk(FSCACHE, "NFS:    readpage_from_fscache %d\n", ret);
+                nfs_add_fscache_stats(inode, NFSIOS_FSCACHE_PAGES_READ_FAIL, 1);
+        }
+        return ret;
+}
+
+/*
+ * Retrieve a set of pages from fscache
+ */
+int __nfs_readpages_from_fscache(struct nfs_open_context *ctx,
+                                 struct inode *inode,
+                                 struct address_space *mapping,
+                                 struct list_head *pages,
+                                 unsigned *nr_pages)
+{
+        int ret, npages = *nr_pages;
+
+        dfprintk(FSCACHE, "NFS: nfs_getpages_from_fscache (0x%p/%u/0x%p)\n",
+                 NFS_I(inode)->fscache, npages, inode);
+
+        ret = fscache_read_or_alloc_pages(NFS_I(inode)->fscache,
+                                          mapping, pages, nr_pages,
+                                          nfs_readpage_from_fscache_complete,
+                                          ctx,
+                                          mapping_gfp_mask(mapping));
+        if (*nr_pages < npages)
+                nfs_add_fscache_stats(inode, NFSIOS_FSCACHE_PAGES_READ_OK,
+                                      npages);
+        if (*nr_pages > 0)
+                nfs_add_fscache_stats(inode, NFSIOS_FSCACHE_PAGES_READ_FAIL,
+                                      *nr_pages);
+
+        switch (ret) {
+        case 0: /* read submitted to the cache for all pages */
+                BUG_ON(!list_empty(pages));
+                BUG_ON(*nr_pages != 0);
+                dfprintk(FSCACHE,
+                         "NFS: nfs_getpages_from_fscache: submitted\n");
+
+                return ret;
+
+        case -ENOBUFS: /* some pages aren't cached and can't be */
+        case -ENODATA: /* some pages aren't cached */
+                dfprintk(FSCACHE,
+                         "NFS: nfs_getpages_from_fscache: no page: %d\n", ret);
+                return 1;
+
+        default:
+                dfprintk(FSCACHE,
+                         "NFS: nfs_getpages_from_fscache: ret  %d\n", ret);
+        }
+
+        return ret;
+}