9p: Add fscache support to 9p
This patch adds a persistent, read-only caching facility for
9p clients using the FS-Cache caching backend.
When the fscache facility is enabled, each inode is associated
with a corresponding vcookie which is an index into the FS-Cache
indexing tree. The FS-Cache indexing tree is indexed at 3 levels:
- session object associated with each mount.
- inode/vcookie
- actual data (pages)
A cache tag is chosen randomly for each session. These tags can
be read off /sys/fs/9p/caches and can be passed as a mount-time
parameter to re-attach to the specified caching session.
Signed-off-by: Abhishek Kulkarni <adkulkar@umail.iu.edu>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>
diff --git a/fs/9p/vfs_addr.c b/fs/9p/vfs_addr.c
index 9282828..90e3844 100644
--- a/fs/9p/vfs_addr.c
+++ b/fs/9p/vfs_addr.c
@@ -38,6 +38,7 @@
#include "v9fs.h"
#include "v9fs_vfs.h"
+#include "cache.h"
/**
* v9fs_vfs_readpage - read an entire page in from 9P
@@ -52,18 +53,31 @@
int retval;
loff_t offset;
char *buffer;
+ struct inode *inode;
+ inode = page->mapping->host;
P9_DPRINTK(P9_DEBUG_VFS, "\n");
+
+ BUG_ON(!PageLocked(page));
+
+ retval = v9fs_readpage_from_fscache(inode, page);
+ if (retval == 0)
+ return retval;
+
buffer = kmap(page);
offset = page_offset(page);
retval = v9fs_file_readn(filp, buffer, NULL, PAGE_CACHE_SIZE, offset);
- if (retval < 0)
+ if (retval < 0) {
+ v9fs_uncache_page(inode, page);
goto done;
+ }
memset(buffer + retval, 0, PAGE_CACHE_SIZE - retval);
flush_dcache_page(page);
SetPageUptodate(page);
+
+ v9fs_readpage_to_fscache(inode, page);
retval = 0;
done:
@@ -72,6 +86,78 @@
return retval;
}
+/**
+ * v9fs_vfs_readpages - read a set of pages from 9P
+ *
+ * @filp: file being read
+ * @mapping: the address space
+ * @pages: list of pages to read
+ * @nr_pages: count of pages to read
+ *
+ */
+
+static int v9fs_vfs_readpages(struct file *filp, struct address_space *mapping,
+ struct list_head *pages, unsigned nr_pages)
+{
+ int ret = 0;
+ struct inode *inode;
+
+ inode = mapping->host;
+ P9_DPRINTK(P9_DEBUG_VFS, "inode: %p file: %p\n", inode, filp);
+
+ ret = v9fs_readpages_from_fscache(inode, mapping, pages, &nr_pages);
+ if (ret == 0)
+ return ret;
+
+ ret = read_cache_pages(mapping, pages, (void *)v9fs_vfs_readpage, filp);
+ P9_DPRINTK(P9_DEBUG_VFS, " = %d\n", ret);
+ return ret;
+}
+
+/**
+ * v9fs_release_page - release the private state associated with a page
+ *
+ * Returns 1 if the page can be released, false otherwise.
+ */
+
+static int v9fs_release_page(struct page *page, gfp_t gfp)
+{
+ if (PagePrivate(page))
+ return 0;
+
+ return v9fs_fscache_release_page(page, gfp);
+}
+
+/**
+ * v9fs_invalidate_page - Invalidate a page completely or partially
+ *
+ * @page: structure to page
+ * @offset: offset in the page
+ */
+
+static void v9fs_invalidate_page(struct page *page, unsigned long offset)
+{
+ if (offset == 0)
+ v9fs_fscache_invalidate_page(page);
+}
+
+/**
+ * v9fs_launder_page - Writeback a dirty page
+ * Since the writes go directly to the server, we simply return a 0
+ * here to indicate success.
+ *
+ * Returns 0 on success.
+ */
+
+static int v9fs_launder_page(struct page *page)
+{
+ return 0;
+}
+
const struct address_space_operations v9fs_addr_operations = {
.readpage = v9fs_vfs_readpage,
+ .readpages = v9fs_vfs_readpages,
+ .releasepage = v9fs_release_page,
+ .invalidatepage = v9fs_invalidate_page,
+ .launder_page = v9fs_launder_page,
};