NFS/SUNRPC: Remove other deadlock-avoidance mechanisms in nfs_release_page()

Now that nfs_release_page() doesn't block indefinitely, other deadlock
avoidance mechanisms aren't needed.
 - it doesn't hurt for kswapd to block occasionally.  If it doesn't
   want to block it would clear __GFP_WAIT.  The current_is_kswapd()
   was only added to avoid deadlocks and we have a new approach for
   that.
 - memory allocation in the SUNRPC layer can very rarely try to
   ->releasepage() a page it is trying to handle.  The deadlock
   is removed as nfs_release_page() doesn't block indefinitely.

So we don't need to set PF_FSTRANS for sunrpc network operations any
more.

Signed-off-by: NeilBrown <neilb@suse.de>
Acked-by: Jeff Layton <jlayton@primarydata.com>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>

1 files changed, 6 insertions, 8 deletions

diff --git a/fs/nfs/file.c b/fs/nfs/file.c
index 24832d0..6920127c 100644
--- a/fs/nfs/file.c
+++ b/fs/nfs/file.c
@@ -476,20 +476,18 @@ static int nfs_release_page(struct page *page, gfp_t gfp)
 	dfprintk(PAGECACHE, "NFS: release_page(%p)\n", page);
 
 	/* Always try to initiate a 'commit' if relevant, but only
-	 * wait for it if __GFP_WAIT is set and the calling process is
-	 * allowed to block.  Even then, only wait 1 second and only
-	 * if the 'bdi' is not congested.
+	 * wait for it if __GFP_WAIT is set.  Even then, only wait 1
+	 * second and only if the 'bdi' is not congested.
 	 * Waiting indefinitely can cause deadlocks when the NFS
-	 * server is on this machine, and there is no particular need
-	 * to wait extensively here.  A short wait has the benefit
-	 * that someone else can worry about the freezer.
+	 * server is on this machine, when a new TCP connection is
+	 * needed and in other rare cases.  There is no particular
+	 * need to wait extensively here.  A short wait has the
+	 * benefit that someone else can worry about the freezer.
 	 */
 	if (mapping) {
 		struct nfs_server *nfss = NFS_SERVER(mapping->host);
 		nfs_commit_inode(mapping->host, 0);
 		if ((gfp & __GFP_WAIT) &&
-		    !current_is_kswapd() &&
-		    !(current->flags & PF_FSTRANS) &&
 		    !bdi_write_congested(&nfss->backing_dev_info)) {
 			wait_on_page_bit_killable_timeout(page, PG_private,
 							  HZ);