NFSv4: Respect the server imposed limit on how many changes we may cache

The NFSv4 delegation spec allows the server to tell a client to limit how
much data it cache after the file is closed. In return, the server
guarantees enough free space to avoid ENOSPC situations, etc.
Prior to this patch, we assumed we could always cache aggressively after
close. Unfortunately, this causes problems with servers that set the
limit to 0 and therefore do not offer any ENOSPC guarantees.

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>

1 files changed, 28 insertions, 1 deletions

diff --git a/fs/nfs/nfs4file.c b/fs/nfs/nfs4file.c
index 43f1590b9240..b0dbe0abed53 100644
--- a/fs/nfs/nfs4file.c
+++ b/fs/nfs/nfs4file.c
@@ -6,7 +6,9 @@
 #include <linux/fs.h>
 #include <linux/falloc.h>
 #include <linux/nfs_fs.h>
+#include "delegation.h"
 #include "internal.h"
+#include "iostat.h"
 #include "fscache.h"
 #include "pnfs.h"
 
@@ -99,6 +101,31 @@ out_drop:
 	goto out_put_ctx;
 }
 
+/*
+ * Flush all dirty pages, and check for write errors.
+ */
+static int
+nfs4_file_flush(struct file *file, fl_owner_t id)
+{
+	struct inode	*inode = file_inode(file);
+
+	dprintk("NFS: flush(%pD2)\n", file);
+
+	nfs_inc_stats(inode, NFSIOS_VFSFLUSH);
+	if ((file->f_mode & FMODE_WRITE) == 0)
+		return 0;
+
+	/*
+	 * If we're holding a write delegation, then check if we're required
+	 * to flush the i/o on close. If not, then just start the i/o now.
+	 */
+	if (!nfs4_delegation_flush_on_close(inode))
+		return filemap_fdatawrite(file->f_mapping);
+
+	/* Flush writes to the server and return any errors */
+	return vfs_fsync(file, 0);
+}
+
 static int
 nfs4_file_fsync(struct file *file, loff_t start, loff_t end, int datasync)
 {
@@ -177,7 +204,7 @@ const struct file_operations nfs4_file_operations = {
 	.write_iter	= nfs_file_write,
 	.mmap		= nfs_file_mmap,
 	.open		= nfs4_file_open,
-	.flush		= nfs_file_flush,
+	.flush		= nfs4_file_flush,
 	.release	= nfs_file_release,
 	.fsync		= nfs4_file_fsync,
 	.lock		= nfs_lock,