[PATCH v4 5/5] nfsd: start non-blocking writeback after adding nfsd_file to the LRU

[Jeff Layton <jlayton@kernel.org>]

When a GC entry gets added to the LRU, kick off SYNC_NONE writeback
so that we can be ready to close it when the time comes. This should
help minimize delays when freeing objects reaped from the LRU.

Signed-off-by: Jeff Layton <jlayton@kernel.org>
---
 fs/nfsd/filecache.c | 23 +++++++++++++++++++++--
 1 file changed, 21 insertions(+), 2 deletions(-)

diff --git a/fs/nfsd/filecache.c b/fs/nfsd/filecache.c
index 47cdc6129a7b..c43b6cff03e2 100644
--- a/fs/nfsd/filecache.c
+++ b/fs/nfsd/filecache.c
@@ -325,6 +325,20 @@ nfsd_file_fsync(struct nfsd_file *nf)
 		nfsd_reset_write_verifier(net_generic(nf->nf_net, nfsd_net_id));
 }
 
+static void
+nfsd_file_flush(struct nfsd_file *nf)
+{
+	struct file *file = nf->nf_file;
+	struct address_space *mapping;
+
+	if (!file || !(file->f_mode & FMODE_WRITE))
+		return;
+
+	mapping = file->f_mapping;
+	if (mapping_tagged(mapping, PAGECACHE_TAG_DIRTY))
+		filemap_flush(mapping);
+}
+
 static int
 nfsd_file_check_write_error(struct nfsd_file *nf)
 {
@@ -484,9 +498,14 @@ nfsd_file_put(struct nfsd_file *nf)
 
 		/* Try to add it to the LRU.  If that fails, decrement. */
 		if (nfsd_file_lru_add(nf)) {
-			/* If it's still hashed, we're done */
-			if (test_bit(NFSD_FILE_HASHED, &nf->nf_flags))
+			/*
+			 * If it's still hashed, we can just return now,
+			 * after kicking off SYNC_NONE writeback.
+			 */
+			if (test_bit(NFSD_FILE_HASHED, &nf->nf_flags)) {
+				nfsd_file_flush(nf);
 				return;
+			}
 
 			/*
 			 * We're racing with unhashing, so try to remove it from
-- 
2.38.1