[PATCH 34/37] NFS: Read pages from FS-Cache into an NFS inode

David Howells
2008-02-08T17:14:45Z

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

Signed-off-by: David Howells <dhowells@redhat.com>
---

fs/nfs/fscache.c | 112 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
fs/nfs/fscache.h | 47 +++++++++++++++++++++++
fs/nfs/read.c | 18 +++++++++
3 files changed, 176 insertions(+), 1 deletions(-)

diff --git a/fs/nfs/fscache.c b/fs/nfs/fscache.c
index d475ff5..438cc9b 100644
--- a/fs/nfs/fscache.c
+++ b/fs/nfs/fscache.c
@@ -344,5 +344,115 @@ void __nfs_fscache_invalidate_page(struct page *page, struct inode *inode)

BUG_ON(!PageLocked(page));
fscache_uncache_page(nfsi->fscache, page);
- nfs_add_stats(page->mapping->host, NFSIOS_FSCACHE_UNCACHE, 1);
+ nfs_add_stats(inode, NFSIOS_FSCACHE_UNCACHE, 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_stats(inode, NFSIOS_FSCACHE_READ_OK, 1);
+ return ret;
+
+ case -ENOBUFS: /* inode not in cache */
+ case -ENODATA: /* page not in cache */
+ nfs_add_stats(inode, NFSIOS_FSCACHE_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_stats(inode, NFSIOS_FSCACHE_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_stats(inode, NFSIOS_FSCACHE_READ_OK, npages);
+ if (*nr_pages > 0)
+ nfs_add_stats(inode, NFSIOS_FSCACHE_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 1cb7d96..4c1e1a8 100644
--- a/fs/nfs/fscache.h
+++ b/fs/nfs/fscache.h
@@ -89,6 +89,12 @@ extern void nfs_fscache_attr_changed(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 *);
+
/*
* release the caching state associated with a page if undergoing complete page
* invalidation
@@ -100,6 +106,32 @@ 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; }
@@ -132,5 +164,20 @@ static inline int nfs_fscache_release_page(struct page *page, gfp_t gfp)
static inline void nfs_fscache_invalidate_page(struct page *page,
struct inode *inode) {}

+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 725a5a2..db27b26 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

@@ -493,9 +494,16 @@ int nfs_readpage(struct file *file, struct page *page)
goto out_unlock;
} 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:
@@ -571,6 +579,15 @@ 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
@@ -581,6 +598,7 @@ 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;