NFS: kswapd must not block in nfs_release_page

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>
Cc: stable@kernel.org

2 files changed, 13 insertions, 4 deletions

diff --git a/fs/nfs/file.c b/fs/nfs/file.c
index 36a5e74f51b4..f036153d9f50 100644
--- a/fs/nfs/file.c
+++ b/fs/nfs/file.c
@@ -27,6 +27,7 @@
 #include <linux/pagemap.h>
 #include <linux/aio.h>
 #include <linux/gfp.h>
+#include <linux/swap.h>
 
 #include <asm/uaccess.h>
 #include <asm/system.h>
@@ -493,11 +494,19 @@ 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;
diff --git a/fs/nfs/write.c b/fs/nfs/write.c
index 91679e2631ee..0a6c65a1f9d7 100644
--- a/fs/nfs/write.c
+++ b/fs/nfs/write.c
@@ -1379,7 +1379,7 @@ static const struct rpc_call_ops nfs_commit_ops = {
         .rpc_release = nfs_commit_release,
 };
 
-static int nfs_commit_inode(struct inode *inode, int how)
+int nfs_commit_inode(struct inode *inode, int how)
 {
         LIST_HEAD(head);
         int may_wait = how & FLUSH_SYNC;
@@ -1443,7 +1443,7 @@ out_mark_dirty:
         return ret;
 }
 #else
-static int nfs_commit_inode(struct inode *inode, int how)
+int nfs_commit_inode(struct inode *inode, int how)
 {
         return 0;
 }