NFS: Adapt readdirplus to application usage patterns
While the use of READDIRPLUS is significantly more efficient than
READDIR followed by many LOOKUP calls, it is still less efficient
than just READDIR if the attributes are not required.
This patch tracks when lookups are attempted on the directory,
and uses that information to selectively disable READDIRPLUS
on that directory.
The first 'readdir' call is always served using READDIRPLUS.
Subsequent calls only use READDIRPLUS if there was a successful
lookup or revalidation on a child in the mean time.
Credit for the original idea should go to Neil Brown. See:
http://www.spinics.net/lists/linux-nfs/msg19996.html
However, the implementation in this patch differs from Neil's
in that it focuses on tracking lookups rather than calls to
stat().
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Cc: Neil Brown <neilb@suse.de>
diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
index 82b42e2..d0884c0 100644
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -475,6 +475,29 @@
}
static
+bool nfs_use_readdirplus(struct inode *dir, struct file *filp)
+{
+ if (!nfs_server_capable(dir, NFS_CAP_READDIRPLUS))
+ return false;
+ if (test_and_clear_bit(NFS_INO_ADVISE_RDPLUS, &NFS_I(dir)->flags))
+ return true;
+ if (filp->f_pos == 0)
+ return true;
+ return false;
+}
+
+/*
+ * This function is called by the lookup code to request the use of
+ * readdirplus to accelerate any future lookups in the same
+ * directory.
+ */
+static
+void nfs_advise_use_readdirplus(struct inode *dir)
+{
+ set_bit(NFS_INO_ADVISE_RDPLUS, &NFS_I(dir)->flags);
+}
+
+static
void nfs_prime_dcache(struct dentry *parent, struct nfs_entry *entry)
{
struct qstr filename = {
@@ -874,7 +897,7 @@
desc->file = filp;
desc->dir_cookie = &dir_ctx->dir_cookie;
desc->decode = NFS_PROTO(inode)->decode_dirent;
- desc->plus = NFS_USE_READDIRPLUS(inode);
+ desc->plus = nfs_use_readdirplus(inode, filp) ? 1 : 0;
nfs_block_sillyrename(dentry);
res = nfs_revalidate_mapping(inode, filp->f_mapping);
@@ -1114,7 +1137,7 @@
if (!inode) {
if (nfs_neg_need_reval(dir, dentry, nd))
goto out_bad;
- goto out_valid;
+ goto out_valid_noent;
}
if (is_bad_inode(inode)) {
@@ -1156,6 +1179,9 @@
out_set_verifier:
nfs_set_verifier(dentry, nfs_save_change_attribute(dir));
out_valid:
+ /* Success: notify readdir to use READDIRPLUS */
+ nfs_advise_use_readdirplus(dir);
+ out_valid_noent:
dput(parent);
dfprintk(LOOKUPCACHE, "NFS: %s(%s/%s) is valid\n",
__func__, dentry->d_parent->d_name.name,
@@ -1311,6 +1337,9 @@
if (IS_ERR(res))
goto out_unblock_sillyrename;
+ /* Success: notify readdir to use READDIRPLUS */
+ nfs_advise_use_readdirplus(dir);
+
no_entry:
res = d_materialise_unique(dentry, inode);
if (res != NULL) {