vfs: make it possible to access the dentry hash/len as one 64-bit entry
This allows comparing hash and len in one operation on 64-bit
architectures. Right now only __d_lookup_rcu() takes advantage of this,
since that is the case we care most about.
The use of anonymous struct/unions hides the alternate 64-bit approach
from most users, the exception being a few cases where we initialize a
'struct qstr' with a static initializer. This makes the problematic
cases use a new QSTR_INIT() helper function for that (but initializing
just the name pointer with a "{ .name = xyzzy }" initializer remains
valid, as does just copying another qstr structure).
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/fs/dcache.c b/fs/dcache.c
index e6707a1..92099f6 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -1502,7 +1502,7 @@
struct dentry *res = NULL;
if (root_inode) {
- static const struct qstr name = { .name = "/", .len = 1 };
+ static const struct qstr name = QSTR_INIT("/", 1);
res = __d_alloc(root_inode->i_sb, &name);
if (res)
@@ -1816,10 +1816,9 @@
const struct qstr *name,
unsigned *seqp, struct inode *inode)
{
- unsigned int len = name->len;
- unsigned int hash = name->hash;
+ u64 hashlen = name->hash_len;
const unsigned char *str = name->name;
- struct hlist_bl_head *b = d_hash(parent, hash);
+ struct hlist_bl_head *b = d_hash(parent, hashlen_hash(hashlen));
struct hlist_bl_node *node;
struct dentry *dentry;
@@ -1846,9 +1845,6 @@
hlist_bl_for_each_entry_rcu(dentry, node, b, d_hash) {
unsigned seq;
- if (dentry->d_name.hash != hash)
- continue;
-
seqretry:
/*
* The dentry sequence count protects us from concurrent
@@ -1871,6 +1867,8 @@
*seqp = seq;
if (unlikely(parent->d_flags & DCACHE_OP_COMPARE)) {
+ if (dentry->d_name.hash != hashlen_hash(hashlen))
+ continue;
switch (slow_dentry_cmp(parent, inode, dentry, seq, name)) {
case D_COMP_OK:
return dentry;
@@ -1881,9 +1879,9 @@
}
}
- if (dentry->d_name.len != len)
+ if (dentry->d_name.hash_len != hashlen)
continue;
- if (!dentry_cmp(dentry, str, len))
+ if (!dentry_cmp(dentry, str, hashlen_len(hashlen)))
return dentry;
}
return NULL;