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authorLinus Torvalds <torvalds@linux-foundation.org>2024-06-10 20:47:06 +0200
committerLinus Torvalds <torvalds@linux-foundation.org>2024-06-19 21:34:34 +0200
commite60cc61153e61e4e38bd983492df9959e82ae4dc (patch)
treec3e9b33a0ad49b111aa0f9a13fe43ec8c04a0894 /fs/dcache.c
parentLinux 6.10-rc4 (diff)
downloadlinux-e60cc61153e61e4e38bd983492df9959e82ae4dc.tar.xz
linux-e60cc61153e61e4e38bd983492df9959e82ae4dc.zip
vfs: dcache: move hashlen_hash() from callers into d_hash()
Both __d_lookup_rcu() and __d_lookup_rcu_op_compare() have the full 'name_hash' value of the qstr that they want to look up, and mask it off to just the low 32-bit hash before calling down to d_hash(). Other callers just load the 32-bit hash and pass it as the argument. If we move the masking into d_hash() itself, it simplifies the two callers that currently do the masking, and is a no-op for the other cases. It doesn't actually change the generated code since the compiler will inline d_hash() and see that the end result is the same. [ Technically, since the parse tree changes, the code generation may not be 100% the same, and for me on x86-64, this does result in gcc switching the operands around for one 'cmpl' instruction. So not necessarily the exact same code generation, but equivalent ] However, this does encapsulate the 'd_hash()' operation more, and makes the shift operation in particular be a "shift 32 bits right, return full word". Which matches the instruction semantics on both x86-64 and arm64 better, since a 32-bit shift will clear the upper bits. That makes the next step of introducing a "shift by runtime constant" more obvious and generates the shift with no extraneous type masking. Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs/dcache.c')
-rw-r--r--fs/dcache.c8
1 files changed, 4 insertions, 4 deletions
diff --git a/fs/dcache.c b/fs/dcache.c
index 407095188f83..8b4382f5c99d 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -100,9 +100,9 @@ static unsigned int d_hash_shift __ro_after_init;
static struct hlist_bl_head *dentry_hashtable __ro_after_init;
-static inline struct hlist_bl_head *d_hash(unsigned int hash)
+static inline struct hlist_bl_head *d_hash(unsigned long hashlen)
{
- return dentry_hashtable + (hash >> d_hash_shift);
+ return dentry_hashtable + ((u32)hashlen >> d_hash_shift);
}
#define IN_LOOKUP_SHIFT 10
@@ -2104,7 +2104,7 @@ static noinline struct dentry *__d_lookup_rcu_op_compare(
unsigned *seqp)
{
u64 hashlen = name->hash_len;
- struct hlist_bl_head *b = d_hash(hashlen_hash(hashlen));
+ struct hlist_bl_head *b = d_hash(hashlen);
struct hlist_bl_node *node;
struct dentry *dentry;
@@ -2171,7 +2171,7 @@ struct dentry *__d_lookup_rcu(const struct dentry *parent,
{
u64 hashlen = name->hash_len;
const unsigned char *str = name->name;
- struct hlist_bl_head *b = d_hash(hashlen_hash(hashlen));
+ struct hlist_bl_head *b = d_hash(hashlen);
struct hlist_bl_node *node;
struct dentry *dentry;