fs: dcache reduce branches in lookup path
Reduce some branches and memory accesses in dcache lookup by adding dentry
flags to indicate common d_ops are set, rather than having to check them.
This saves a pointer memory access (dentry->d_op) in common path lookup
situations, and saves another pointer load and branch in cases where we
have d_op but not the particular operation.
Patched with:
git grep -E '[.>]([[:space:]])*d_op([[:space:]])*=' | xargs sed -e 's/\([^\t ]*\)->d_op = \(.*\);/d_set_d_op(\1, \2);/' -e 's/\([^\t ]*\)\.d_op = \(.*\);/d_set_d_op(\&\1, \2);/' -i
Signed-off-by: Nick Piggin <npiggin@kernel.dk>
diff --git a/fs/namei.c b/fs/namei.c
index c731b50..90bd287 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -587,6 +587,17 @@
return dentry;
}
+static inline int need_reval_dot(struct dentry *dentry)
+{
+ if (likely(!(dentry->d_flags & DCACHE_OP_REVALIDATE)))
+ return 0;
+
+ if (likely(!(dentry->d_sb->s_type->fs_flags & FS_REVAL_DOT)))
+ return 0;
+
+ return 1;
+}
+
/*
* force_reval_path - force revalidation of a dentry
*
@@ -610,10 +621,9 @@
/*
* only check on filesystems where it's possible for the dentry to
- * become stale. It's assumed that if this flag is set then the
- * d_revalidate op will also be defined.
+ * become stale.
*/
- if (!(dentry->d_sb->s_type->fs_flags & FS_REVAL_DOT))
+ if (!need_reval_dot(dentry))
return 0;
status = dentry->d_op->d_revalidate(dentry, nd);
@@ -1003,7 +1013,7 @@
* See if the low-level filesystem might want
* to use its own hash..
*/
- if (parent->d_op && parent->d_op->d_hash) {
+ if (unlikely(parent->d_flags & DCACHE_OP_HASH)) {
int err = parent->d_op->d_hash(parent, nd->inode, name);
if (err < 0)
return err;
@@ -1029,7 +1039,7 @@
return -ECHILD;
nd->seq = seq;
- if (dentry->d_op && dentry->d_op->d_revalidate) {
+ if (dentry->d_flags & DCACHE_OP_REVALIDATE) {
/* We commonly drop rcu-walk here */
if (nameidata_dentry_drop_rcu(nd, dentry))
return -ECHILD;
@@ -1043,7 +1053,7 @@
if (!dentry)
goto need_lookup;
found:
- if (dentry->d_op && dentry->d_op->d_revalidate)
+ if (dentry->d_flags & DCACHE_OP_REVALIDATE)
goto need_revalidate;
done:
path->mnt = mnt;
@@ -1281,8 +1291,7 @@
* We bypassed the ordinary revalidation routines.
* We may need to check the cached dentry for staleness.
*/
- if (nd->path.dentry && nd->path.dentry->d_sb &&
- (nd->path.dentry->d_sb->s_type->fs_flags & FS_REVAL_DOT)) {
+ if (need_reval_dot(nd->path.dentry)) {
if (nameidata_drop_rcu_maybe(nd))
return -ECHILD;
err = -ESTALE;
@@ -1602,7 +1611,7 @@
* See if the low-level filesystem might want
* to use its own hash..
*/
- if (base->d_op && base->d_op->d_hash) {
+ if (base->d_flags & DCACHE_OP_HASH) {
err = base->d_op->d_hash(base, inode, name);
dentry = ERR_PTR(err);
if (err < 0)
@@ -1616,7 +1625,7 @@
*/
dentry = d_lookup(base, name);
- if (dentry && dentry->d_op && dentry->d_op->d_revalidate)
+ if (dentry && (dentry->d_flags & DCACHE_OP_REVALIDATE))
dentry = do_revalidate(dentry, nd);
if (!dentry)
@@ -2070,7 +2079,7 @@
follow_dotdot(nd);
dir = nd->path.dentry;
case LAST_DOT:
- if (nd->path.mnt->mnt_sb->s_type->fs_flags & FS_REVAL_DOT) {
+ if (need_reval_dot(dir)) {
if (!dir->d_op->d_revalidate(dir, nd)) {
error = -ESTALE;
goto exit;