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authorLinus Torvalds <torvalds@linux-foundation.org>2012-03-02 14:49:24 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2012-03-02 14:49:24 -0800
commit200e9ef7ab51f3dce4f35f90ea458cf43ea83bb8 (patch)
tree0fb908e21482546aef9c9fff5580ca79fec1cd56
parent5707c87f20bca9e76969bb4096149de6ef74cbb9 (diff)
downloadlinux-stericsson-200e9ef7ab51f3dce4f35f90ea458cf43ea83bb8.tar.gz
vfs: split up name hashing in link_path_walk() into helper function
The code in link_path_walk() that finds out the length and the hash of the next path component is some of the hottest code in the kernel. And I have a version of it that does things at the full width of the CPU wordsize at a time, but that means that we *really* want to split it up into a separate helper function. So this re-organizes the code a bit and splits the hashing part into a helper function called "hash_name()". It returns the length of the pathname component, while at the same time computing and writing the hash to the appropriate location. The code generation is slightly changed by this patch, but generally for the better - and the added abstraction actually makes the code easier to read too. And the new interface is well suited for replacing just the "hash_name()" function with alternative implementations. Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--fs/namei.c52
1 files changed, 34 insertions, 18 deletions
diff --git a/fs/namei.c b/fs/namei.c
index ec72fa1acb14..71807dc7e402 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1383,6 +1383,25 @@ unsigned int full_name_hash(const unsigned char *name, unsigned int len)
}
/*
+ * We know there's a real path component here of at least
+ * one character.
+ */
+static inline unsigned long hash_name(const char *name, unsigned int *hashp)
+{
+ unsigned long hash = init_name_hash();
+ unsigned long len = 0, c;
+
+ c = (unsigned char)*name;
+ do {
+ len++;
+ hash = partial_name_hash(c, hash);
+ c = (unsigned char)name[len];
+ } while (c && c != '/');
+ *hashp = end_name_hash(hash);
+ return len;
+}
+
+/*
* Name resolution.
* This is the basic name resolution function, turning a pathname into
* the final dentry. We expect 'base' to be positive and a directory.
@@ -1402,31 +1421,22 @@ static int link_path_walk(const char *name, struct nameidata *nd)
/* At this point we know we have a real path component. */
for(;;) {
- unsigned long hash;
struct qstr this;
- unsigned int c;
+ long len;
int type;
err = may_lookup(nd);
if (err)
break;
+ len = hash_name(name, &this.hash);
this.name = name;
- c = *(const unsigned char *)name;
-
- hash = init_name_hash();
- do {
- name++;
- hash = partial_name_hash(c, hash);
- c = *(const unsigned char *)name;
- } while (c && (c != '/'));
- this.len = name - (const char *) this.name;
- this.hash = end_name_hash(hash);
+ this.len = len;
type = LAST_NORM;
- if (this.name[0] == '.') switch (this.len) {
+ if (name[0] == '.') switch (len) {
case 2:
- if (this.name[1] == '.') {
+ if (name[1] == '.') {
type = LAST_DOTDOT;
nd->flags |= LOOKUP_JUMPED;
}
@@ -1445,12 +1455,18 @@ static int link_path_walk(const char *name, struct nameidata *nd)
}
}
- /* remove trailing slashes? */
- if (!c)
+ if (!name[len])
goto last_component;
- while (*++name == '/');
- if (!*name)
+ /*
+ * If it wasn't NUL, we know it was '/'. Skip that
+ * slash, and continue until no more slashes.
+ */
+ do {
+ len++;
+ } while (unlikely(name[len] == '/'));
+ if (!name[len])
goto last_component;
+ name += len;
err = walk_component(nd, &next, &this, type, LOOKUP_FOLLOW);
if (err < 0)