[PATCH v2 3/3] nfsd: start non-blocking writeback after adding nfsd_file to the LRU

[Jeff Layton <jlayton@xxxxxxxxxx>]

When a GC entry gets added to the LRU, kick off SYNC_NONE writeback
so that we can be ready to close it out when the time comes.

Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx>
---
 fs/nfsd/filecache.c | 37 +++++++++++++++++++++++++++++++------
 1 file changed, 31 insertions(+), 6 deletions(-)

diff --git a/fs/nfsd/filecache.c b/fs/nfsd/filecache.c
index d2bbded805d4..491d3d9a1870 100644
--- a/fs/nfsd/filecache.c
+++ b/fs/nfsd/filecache.c
@@ -316,7 +316,7 @@ nfsd_file_alloc(struct nfsd_file_lookup_key *key, unsigned int may)
 }
 
 static void
-nfsd_file_flush(struct nfsd_file *nf)
+nfsd_file_fsync(struct nfsd_file *nf)
 {
 	struct file *file = nf->nf_file;
 
@@ -327,6 +327,22 @@ nfsd_file_flush(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;
+	unsigned long nrpages;
+
+	if (!file || !(file->f_mode & FMODE_WRITE))
+		return;
+
+	nrpages = file->f_mapping->nrpages;
+	if (nrpages) {
+		this_cpu_add(nfsd_file_pages_flushed, nrpages);
+		filemap_flush(file->f_mapping);
+	}
+}
+
 static void
 nfsd_file_free(struct nfsd_file *nf)
 {
@@ -337,7 +353,7 @@ nfsd_file_free(struct nfsd_file *nf)
 	this_cpu_inc(nfsd_file_releases);
 	this_cpu_add(nfsd_file_total_age, age);
 
-	nfsd_file_flush(nf);
+	nfsd_file_fsync(nf);
 
 	if (nf->nf_mark)
 		nfsd_file_mark_put(nf->nf_mark);
@@ -500,12 +516,21 @@ nfsd_file_put(struct nfsd_file *nf)
 
 	if (test_bit(NFSD_FILE_GC, &nf->nf_flags)) {
 		/*
-		 * If this is the last reference (nf_ref == 1), then transfer
-		 * it to the LRU. If the add to the LRU fails, just put it as
-		 * usual.
+		 * If this is the last reference (nf_ref == 1), then try
+		 * to transfer it to the LRU.
+		 */
+		if (refcount_dec_not_one(&nf->nf_ref))
+			return;
+
+		/*
+		 * If the add to the list succeeds, try to kick off SYNC_NONE
+		 * writeback. If the add fails, then just fall through to
+		 * decrement as usual.
 		 */
-		if (refcount_dec_not_one(&nf->nf_ref) || nfsd_file_lru_add(nf))
+		if (nfsd_file_lru_add(nf)) {
+			nfsd_file_flush(nf);
 			return;
+		}
 	}
 	__nfsd_file_put(nf);
 }
-- 
2.37.3