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>

3 files changed, 177 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;
+}
diff --git a/fs/nfs/fscache.h b/fs/nfs/fscache.h
index e29613a8cbd2..099349c171ca 100644
--- a/fs/nfs/fscache.h
+++ b/fs/nfs/fscache.h
@@ -86,6 +86,12 @@ extern void nfs_fscache_reset_inode_cookie(struct inode *);
 extern void __nfs_fscache_invalidate_page(struct page *, struct inode *);
 extern int nfs_fscache_release_page(struct page *, gfp_t);
 
+extern int __nfs_readpage_from_fscache(struct nfs_open_context *,
+                                       struct inode *, struct page *);
+extern int __nfs_readpages_from_fscache(struct nfs_open_context *,
+                                        struct inode *, struct address_space *,
+                                        struct list_head *, unsigned *);
+
 /*
  * wait for a page to complete writing to the cache
  */
@@ -107,6 +113,32 @@ static inline void nfs_fscache_invalidate_page(struct page *page,
                 __nfs_fscache_invalidate_page(page, inode);
 }
 
+/*
+ * Retrieve a page from an inode data storage object.
+ */
+static inline int nfs_readpage_from_fscache(struct nfs_open_context *ctx,
+                                            struct inode *inode,
+                                            struct page *page)
+{
+        if (NFS_I(inode)->fscache)
+                return __nfs_readpage_from_fscache(ctx, inode, page);
+        return -ENOBUFS;
+}
+
+/*
+ * Retrieve a set of pages from an inode data storage object.
+ */
+static inline int nfs_readpages_from_fscache(struct nfs_open_context *ctx,
+                                             struct inode *inode,
+                                             struct address_space *mapping,
+                                             struct list_head *pages,
+                                             unsigned *nr_pages)
+{
+        if (NFS_I(inode)->fscache)
+                return __nfs_readpages_from_fscache(ctx, inode, mapping, pages,
+                                                    nr_pages);
+        return -ENOBUFS;
+}
 
 #else /* CONFIG_NFS_FSCACHE */
 static inline int nfs_fscache_register(void) { return 0; }
@@ -138,5 +170,20 @@ static inline void nfs_fscache_invalidate_page(struct page *page,
 static inline void nfs_fscache_wait_on_page_write(struct nfs_inode *nfsi,
                                                   struct page *page) {}
 
+static inline int nfs_readpage_from_fscache(struct nfs_open_context *ctx,
+                                            struct inode *inode,
+                                            struct page *page)
+{
+        return -ENOBUFS;
+}
+static inline int nfs_readpages_from_fscache(struct nfs_open_context *ctx,
+                                             struct inode *inode,
+                                             struct address_space *mapping,
+                                             struct list_head *pages,
+                                             unsigned *nr_pages)
+{
+        return -ENOBUFS;
+}
+
 #endif /* CONFIG_NFS_FSCACHE */
 #endif /* _NFS_FSCACHE_H */
diff --git a/fs/nfs/read.c b/fs/nfs/read.c
index 98b74009c9d7..e18ba792872f 100644
--- a/fs/nfs/read.c
+++ b/fs/nfs/read.c
@@ -24,6 +24,7 @@
 
 #include "internal.h"
 #include "iostat.h"
+#include "fscache.h"
 
 #define NFSDBG_FACILITY         NFSDBG_PAGECACHE
 
@@ -510,8 +511,15 @@ int nfs_readpage(struct file *file, struct page *page)
         } else
                 ctx = get_nfs_open_context(nfs_file_open_context(file));
 
+        if (!IS_SYNC(inode)) {
+                error = nfs_readpage_from_fscache(ctx, inode, page);
+                if (error == 0)
+                        goto out;
+        }
+
         error = nfs_readpage_async(ctx, inode, page);
 
+out:
         put_nfs_open_context(ctx);
         return error;
 out_unlock:
@@ -584,6 +592,15 @@ int nfs_readpages(struct file *filp, struct address_space *mapping,
                         return -EBADF;
         } else
                 desc.ctx = get_nfs_open_context(nfs_file_open_context(filp));
+
+        /* attempt to read as many of the pages as possible from the cache
+         * - this returns -ENOBUFS immediately if the cookie is negative
+         */
+        ret = nfs_readpages_from_fscache(desc.ctx, inode, mapping,
+                                         pages, &nr_pages);
+        if (ret == 0)
+                goto read_complete; /* all pages were read */
+
         if (rsize < PAGE_CACHE_SIZE)
                 nfs_pageio_init(&pgio, inode, nfs_pagein_multi, rsize, 0);
         else
@@ -594,6 +611,7 @@ int nfs_readpages(struct file *filp, struct address_space *mapping,
         nfs_pageio_complete(&pgio);
         npages = (pgio.pg_bytes_written + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
         nfs_add_stats(inode, NFSIOS_READPAGES, npages);
+read_complete:
         put_nfs_open_context(desc.ctx);
 out:
         return ret;