[05/34] NFS: kswapd must not block in nfs_release_page

[Greg KH <gregkh@suse.de>]

2.6.32-stable review patch.  If anyone has any objections, please let us know.

------------------

commit b608b283a962caaa280756bc8563016a71712acf upstream

See https://bugzilla.kernel.org/show_bug.cgi?id=16056

If other processes are blocked waiting for kswapd to free up some memory so
that they can make progress, then we cannot allow kswapd to block on those
processes.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
 fs/nfs/file.c |   14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

--- a/fs/nfs/file.c
+++ b/fs/nfs/file.c
@@ -27,6 +27,8 @@
 #include <linux/slab.h>
 #include <linux/pagemap.h>
 #include <linux/aio.h>
+#include <linux/gfp.h>
+#include <linux/swap.h>
 
 #include <asm/uaccess.h>
 #include <asm/system.h>
@@ -484,11 +486,19 @@ static void nfs_invalidate_page(struct p
  */
 static int nfs_release_page(struct page *page, gfp_t gfp)
 {
+	struct address_space *mapping = page->mapping;
+
 	dfprintk(PAGECACHE, "NFS: release_page(%p)\n", page);
 
 	/* Only do I/O if gfp is a superset of GFP_KERNEL */
-	if ((gfp & GFP_KERNEL) == GFP_KERNEL)
-		nfs_wb_page(page->mapping->host, page);
+	if (mapping && (gfp & GFP_KERNEL) == GFP_KERNEL) {
+		int how = FLUSH_SYNC;
+
+		/* Don't let kswapd deadlock waiting for OOM RPC calls */
+		if (current_is_kswapd())
+			how = 0;
+		nfs_commit_inode(mapping->host, how);
+	}
 	/* If PagePrivate() is set, then the page is not freeable */
 	if (PagePrivate(page))
 		return 0;