NFS: kswapd must not block in nfs_release_page

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>

diff --git a/fs/nfs/file.c b/fs/nfs/file.c
index 61b3bf503ee157d8243259d41e3d7e13765b27f8..9f83d9fe9a61af75574782c310d27ee78f03017a 100644 (file)
--- 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 page *page, unsigned long offset)
  */
 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;