NFS: Add read context retention for FS-Cache to call back with

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From: Linux Kernel Mailing List
Date: Friday, April 3, 2009 - 11:10 am

Gitweb:     http://git.kernel.org/linus/1fcdf534885b65e6d39780a5a89e9dfc5431cf68
Commit:     1fcdf534885b65e6d39780a5a89e9dfc5431cf68
Parent:     545db45f0fc0d4203b045047798ce156972a3056
Author:     David Howells <dhowells@redhat.com>
AuthorDate: Fri Apr 3 16:42:44 2009 +0100
Committer:  David Howells <dhowells@redhat.com>
CommitDate: Fri Apr 3 16:42:44 2009 +0100

    NFS: Add read context retention for FS-Cache to call back with
    
    Add read context retention so that FS-Cache can call back into NFS when a read
    operation on the cache fails EIO rather than reading data.  This permits NFS to
    then fetch the data from the server instead using the appropriate security
    context.
    
    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>
---
 fs/nfs/fscache-index.c |   26 ++++++++++++++++++++++++++
 1 files changed, 26 insertions(+), 0 deletions(-)

diff --git a/fs/nfs/fscache-index.c b/fs/nfs/fscache-index.c
index a119b56..5b10064 100644
--- a/fs/nfs/fscache-index.c
+++ b/fs/nfs/fscache-index.c
@@ -292,6 +292,30 @@ static void nfs_fscache_inode_now_uncached(void *cookie_netfs_data)
 }
 
 /*
+ * Get an extra reference on a read context.
+ * - This function can be absent if the completion function doesn't require a
+ *   context.
+ * - The read context is passed back to NFS in the event that a data read on the
+ *   cache fails with EIO - in which case the server must be contacted to
+ *   retrieve the data, which requires the read context for security.
+ */
+static void nfs_fh_get_context(void *cookie_netfs_data, void *context)
+{
+	get_nfs_open_context(context);
+}
+
+/*
+ * Release an extra reference on a read context.
+ * - This function can be absent if the completion function doesn't require a
+ *   context.
+ */
+static void nfs_fh_put_context(void *cookie_netfs_data, void *context)
+{
+	if (context)
+		put_nfs_open_context(context);
+}
+
+/*
  * Define the inode object for FS-Cache.  This is used to describe an inode
  * object to fscache_acquire_cookie().  It is keyed by the NFS file handle for
  * an inode.
@@ -308,4 +332,6 @@ const struct fscache_cookie_def nfs_fscache_inode_object_def = {
 	.get_aux	= nfs_fscache_inode_get_aux,
 	.check_aux	= nfs_fscache_inode_check_aux,
 	.now_uncached	= nfs_fscache_inode_now_uncached,
+	.get_context	= nfs_fh_get_context,
+	.put_context	= nfs_fh_put_context,
 };
--
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NFS: Add read context retention for FS-Cache to call back with, Linux Kernel Mailing ..., (Fri Apr 3, 11:10 am)