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vfs: link_path_walk: move more of the name hashing into hash_name()

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This avoids having to return the length of the component entirely by
just doing all of the name processing in hash_name().  We can just
return the end of the path component, and a flag for the DOT and DOTDOT
cases.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Linus Torvalds 2024-06-17 09:05:52 -07:00
parent 58b0afa038
commit 13694f0dbc
1 changed files with 32 additions and 19 deletions
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51
fs/namei.c
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@ -2174,21 +2174,37 @@ EXPORT_SYMBOL(hashlen_string);
* Calculate the length and hash of the path component, and
* return the length as the result.
*/
static inline unsigned long hash_name(struct nameidata *nd,
const char *name,
unsigned long *lastword)
static inline const char *hash_name(struct nameidata *nd,
const char *name,
unsigned long *lastword)
{
unsigned long a = 0, b, x = 0, y = (unsigned long)nd->path.dentry;
unsigned long a, b, x, y = (unsigned long)nd->path.dentry;
unsigned long adata, bdata, mask, len;
const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS;
len = 0;
goto inside;
/*
* The first iteration is special, because it can result in
* '.' and '..' and has no mixing other than the final fold.
*/
a = load_unaligned_zeropad(name);
b = a ^ REPEAT_BYTE('/');
if (has_zero(a, &adata, &constants) | has_zero(b, &bdata, &constants)) {
adata = prep_zero_mask(a, adata, &constants);
bdata = prep_zero_mask(b, bdata, &constants);
mask = create_zero_mask(adata | bdata);
a &= zero_bytemask(mask);
*lastword = a;
len = find_zero(mask);
nd->last.hash = fold_hash(a, y);
nd->last.len = len;
return name + len;
}
len = 0;
x = 0;
do {
HASH_MIX(x, y, a);
len += sizeof(unsigned long);
inside:
a = load_unaligned_zeropad(name+len);
b = a ^ REPEAT_BYTE('/');
} while (!(has_zero(a, &adata, &constants) | has_zero(b, &bdata, &constants)));
@ -2197,13 +2213,13 @@ static inline unsigned long hash_name(struct nameidata *nd,
bdata = prep_zero_mask(b, bdata, &constants);
mask = create_zero_mask(adata | bdata);
a &= zero_bytemask(mask);
*lastword = a;
x ^= a;
len += find_zero(mask);
*lastword = 0; // Multi-word components cannot be DOT or DOTDOT
nd->last.hash = fold_hash(x, y);
nd->last.len = len;
return len;
return name + len;
}
/*
@ -2247,7 +2263,7 @@ EXPORT_SYMBOL(hashlen_string);
* We know there's a real path component here of at least
* one character.
*/
static inline unsigned long hash_name(struct nameidata *nd, const char *name, unsigned long *lastword)
static inline const char *hash_name(struct nameidata *nd, const char *name, unsigned long *lastword)
{
unsigned long hash = init_name_hash(nd->path.dentry);
unsigned long len = 0, c, last = 0;
@ -2259,10 +2275,14 @@ static inline unsigned long hash_name(struct nameidata *nd, const char *name, un
hash = partial_name_hash(c, hash);
c = (unsigned char)name[len];
} while (c && c != '/');
// This is reliable for DOT or DOTDOT, since the component
// cannot contain NUL characters - top bits being zero means
// we cannot have had any other pathnames.
*lastword = last;
nd->last.hash = end_name_hash(hash);
nd->last.len = len;
return len;
return name + len;
}
#endif
@ -2301,7 +2321,6 @@ static int link_path_walk(const char *name, struct nameidata *nd)
struct mnt_idmap *idmap;
const char *link;
unsigned long lastword;
unsigned int len;
idmap = mnt_idmap(nd->path.mnt);
err = may_lookup(idmap, nd);
@ -2309,25 +2328,19 @@ static int link_path_walk(const char *name, struct nameidata *nd)
return err;
nd->last.name = name;
len = hash_name(nd, name, &lastword);
name += len;
name = hash_name(nd, name, &lastword);
switch(lastword) {
case LAST_WORD_IS_DOTDOT:
if (len != 2)
goto normal;
nd->last_type = LAST_DOTDOT;
nd->state |= ND_JUMPED;
break;
case LAST_WORD_IS_DOT:
if (len != 1)
goto normal;
nd->last_type = LAST_DOT;
break;
default:
normal:
nd->last_type = LAST_NORM;
nd->state &= ~ND_JUMPED;