[PATCH v2] NFS: Don't invalidate directory mapping until attributes expire

[Benjamin Coddington <bcodding@redhat.com>]

This approach uses another bit in the inode flags..  if that's too expensive
for this ls -l optimization, I will look for another way.

Change from v1:
	Doesn't completely break the commit 311324ad1713 functionality.

8<-----------------------------------------------------------------------------

Commit 311324ad1713666a6e803aecf0d4e1a136a5b34a ("NFS: Be more aggressive
in using readdirplus for 'ls -l' situations") removed the optimization
added by commit 07b5ce8ef2d87f1914054804720d6facbaa3f4ce ("NFS: Make nfs_readdir
revalidate less often") to bypass the revalidation of the directory mapping
on subsequent calls into nfs_readdir().  Add that optimization back here.

A directory modified once every second and containing 40k entries takes my
system around 80 seconds to list.  With this patch, that time is reduced to
7 seconds.

Signed-off-by: Benjamin Coddington <bcodding@redhat.com>
---
 fs/nfs/dir.c           | 3 ++-
 include/linux/nfs_fs.h | 1 +
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
index 19d93d0cd400..88f5dd561025 100644
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -477,6 +477,7 @@ void nfs_force_use_readdirplus(struct inode *dir)
 {
 	if (!list_empty(&NFS_I(dir)->open_files)) {
 		nfs_advise_use_readdirplus(dir);
+		set_bit(NFS_INO_FORCE_RDPLUS, &NFS_I(dir)->flags);
 		nfs_zap_mapping(dir, dir->i_mapping);
 	}
 }
@@ -878,7 +879,7 @@ static bool nfs_dir_mapping_need_revalidate(struct inode *dir)
 
 	if (nfs_attribute_cache_expired(dir))
 		return true;
-	if (nfsi->cache_validity & NFS_INO_INVALID_DATA)
+	if (test_and_clear_bit(NFS_INO_FORCE_RDPLUS, &nfsi->flags))
 		return true;
 	return false;
 }
diff --git a/include/linux/nfs_fs.h b/include/linux/nfs_fs.h
index d71278c3c5bd..729cddb7364f 100644
--- a/include/linux/nfs_fs.h
+++ b/include/linux/nfs_fs.h
@@ -211,6 +211,7 @@ struct nfs_inode {
 #define NFS_INO_LAYOUTCOMMIT	(9)		/* layoutcommit required */
 #define NFS_INO_LAYOUTCOMMITTING (10)		/* layoutcommit inflight */
 #define NFS_INO_LAYOUTSTATS	(11)		/* layoutstats inflight */
+#define NFS_INO_FORCE_RDPLUS	(12)		/* force readdirplus */
 
 static inline struct nfs_inode *NFS_I(const struct inode *inode)
 {
-- 
2.5.5