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-rw-r--r--fs/d_path.c142
1 files changed, 75 insertions, 67 deletions
diff --git a/fs/d_path.c b/fs/d_path.c
index 83db83446afd..06e93dd031bf 100644
--- a/fs/d_path.c
+++ b/fs/d_path.c
@@ -8,12 +8,26 @@
#include <linux/prefetch.h>
#include "mount.h"
-static void prepend(char **buffer, int *buflen, const char *str, int namelen)
+struct prepend_buffer {
+ char *buf;
+ int len;
+};
+#define DECLARE_BUFFER(__name, __buf, __len) \
+ struct prepend_buffer __name = {.buf = __buf + __len, .len = __len}
+
+static char *extract_string(struct prepend_buffer *p)
{
- *buflen -= namelen;
- if (likely(*buflen >= 0)) {
- *buffer -= namelen;
- memcpy(*buffer, str, namelen);
+ if (likely(p->len >= 0))
+ return p->buf;
+ return ERR_PTR(-ENAMETOOLONG);
+}
+
+static void prepend(struct prepend_buffer *p, const char *str, int namelen)
+{
+ p->len -= namelen;
+ if (likely(p->len >= 0)) {
+ p->buf -= namelen;
+ memcpy(p->buf, str, namelen);
}
}
@@ -34,22 +48,22 @@ static void prepend(char **buffer, int *buflen, const char *str, int namelen)
*
* Load acquire is needed to make sure that we see that terminating NUL.
*/
-static bool prepend_name(char **buffer, int *buflen, const struct qstr *name)
+static bool prepend_name(struct prepend_buffer *p, const struct qstr *name)
{
const char *dname = smp_load_acquire(&name->name); /* ^^^ */
u32 dlen = READ_ONCE(name->len);
- char *p;
+ char *s;
- *buflen -= dlen + 1;
- if (unlikely(*buflen < 0))
+ p->len -= dlen + 1;
+ if (unlikely(p->len < 0))
return false;
- p = *buffer -= dlen + 1;
- *p++ = '/';
+ s = p->buf -= dlen + 1;
+ *s++ = '/';
while (dlen--) {
char c = *dname++;
if (!c)
break;
- *p++ = c;
+ *s++ = c;
}
return true;
}
@@ -73,15 +87,14 @@ static bool prepend_name(char **buffer, int *buflen, const struct qstr *name)
*/
static int prepend_path(const struct path *path,
const struct path *root,
- char **buffer, int *buflen)
+ struct prepend_buffer *p)
{
struct dentry *dentry;
struct vfsmount *vfsmnt;
struct mount *mnt;
int error = 0;
unsigned seq, m_seq = 0;
- char *bptr;
- int blen;
+ struct prepend_buffer b;
rcu_read_lock();
restart_mnt:
@@ -89,8 +102,7 @@ restart_mnt:
seq = 0;
rcu_read_lock();
restart:
- bptr = *buffer;
- blen = *buflen;
+ b = *p;
error = 0;
dentry = path->dentry;
vfsmnt = path->mnt;
@@ -105,8 +117,7 @@ restart:
/* Escaped? */
if (dentry != vfsmnt->mnt_root) {
- bptr = *buffer;
- blen = *buflen;
+ b = *p;
error = 3;
break;
}
@@ -127,7 +138,7 @@ restart:
}
parent = dentry->d_parent;
prefetch(parent);
- if (!prepend_name(&bptr, &blen, &dentry->d_name))
+ if (!prepend_name(&b, &dentry->d_name))
break;
dentry = parent;
@@ -148,11 +159,10 @@ restart:
}
done_seqretry(&mount_lock, m_seq);
- if (blen == *buflen)
- prepend(&bptr, &blen, "/", 1);
+ if (b.len == p->len)
+ prepend(&b, "/", 1);
- *buffer = bptr;
- *buflen = blen;
+ *p = b;
return error;
}
@@ -176,24 +186,24 @@ char *__d_path(const struct path *path,
const struct path *root,
char *buf, int buflen)
{
- char *res = buf + buflen;
+ DECLARE_BUFFER(b, buf, buflen);
- prepend(&res, &buflen, "", 1);
- if (prepend_path(path, root, &res, &buflen) > 0)
+ prepend(&b, "", 1);
+ if (prepend_path(path, root, &b) > 0)
return NULL;
- return buflen >= 0 ? res : ERR_PTR(-ENAMETOOLONG);
+ return extract_string(&b);
}
char *d_absolute_path(const struct path *path,
char *buf, int buflen)
{
struct path root = {};
- char *res = buf + buflen;
+ DECLARE_BUFFER(b, buf, buflen);
- prepend(&res, &buflen, "", 1);
- if (prepend_path(path, &root, &res, &buflen) > 1)
+ prepend(&b, "", 1);
+ if (prepend_path(path, &root, &b) > 1)
return ERR_PTR(-EINVAL);
- return buflen >= 0 ? res : ERR_PTR(-ENAMETOOLONG);
+ return extract_string(&b);
}
static void get_fs_root_rcu(struct fs_struct *fs, struct path *root)
@@ -224,7 +234,7 @@ static void get_fs_root_rcu(struct fs_struct *fs, struct path *root)
*/
char *d_path(const struct path *path, char *buf, int buflen)
{
- char *res = buf + buflen;
+ DECLARE_BUFFER(b, buf, buflen);
struct path root;
/*
@@ -245,13 +255,13 @@ char *d_path(const struct path *path, char *buf, int buflen)
rcu_read_lock();
get_fs_root_rcu(current->fs, &root);
if (unlikely(d_unlinked(path->dentry)))
- prepend(&res, &buflen, " (deleted)", 11);
+ prepend(&b, " (deleted)", 11);
else
- prepend(&res, &buflen, "", 1);
- prepend_path(path, &root, &res, &buflen);
+ prepend(&b, "", 1);
+ prepend_path(path, &root, &b);
rcu_read_unlock();
- return buflen >= 0 ? res : ERR_PTR(-ENAMETOOLONG);
+ return extract_string(&b);
}
EXPORT_SYMBOL(d_path);
@@ -278,36 +288,34 @@ char *dynamic_dname(struct dentry *dentry, char *buffer, int buflen,
char *simple_dname(struct dentry *dentry, char *buffer, int buflen)
{
- char *end = buffer + buflen;
+ DECLARE_BUFFER(b, buffer, buflen);
/* these dentries are never renamed, so d_lock is not needed */
- prepend(&end, &buflen, " (deleted)", 11);
- prepend(&end, &buflen, dentry->d_name.name, dentry->d_name.len);
- prepend(&end, &buflen, "/", 1);
- return buflen >= 0 ? end : ERR_PTR(-ENAMETOOLONG);
+ prepend(&b, " (deleted)", 11);
+ prepend(&b, dentry->d_name.name, dentry->d_name.len);
+ prepend(&b, "/", 1);
+ return extract_string(&b);
}
/*
* Write full pathname from the root of the filesystem into the buffer.
*/
-static char *__dentry_path(const struct dentry *d, char *p, int buflen)
+static char *__dentry_path(const struct dentry *d, struct prepend_buffer *p)
{
const struct dentry *dentry;
- char *end;
- int len, seq = 0;
+ struct prepend_buffer b;
+ int seq = 0;
rcu_read_lock();
restart:
dentry = d;
- end = p;
- len = buflen;
+ b = *p;
read_seqbegin_or_lock(&rename_lock, &seq);
while (!IS_ROOT(dentry)) {
const struct dentry *parent = dentry->d_parent;
prefetch(parent);
- if (!prepend_name(&end, &len, &dentry->d_name))
+ if (!prepend_name(&b, &dentry->d_name))
break;
-
dentry = parent;
}
if (!(seq & 1))
@@ -317,28 +325,29 @@ restart:
goto restart;
}
done_seqretry(&rename_lock, seq);
- if (len == buflen)
- prepend(&end, &len, "/", 1);
- return len >= 0 ? end : ERR_PTR(-ENAMETOOLONG);
+ if (b.len == p->len)
+ prepend(&b, "/", 1);
+ return extract_string(&b);
}
char *dentry_path_raw(const struct dentry *dentry, char *buf, int buflen)
{
- char *p = buf + buflen;
- prepend(&p, &buflen, "", 1);
- return __dentry_path(dentry, p, buflen);
+ DECLARE_BUFFER(b, buf, buflen);
+
+ prepend(&b, "", 1);
+ return __dentry_path(dentry, &b);
}
EXPORT_SYMBOL(dentry_path_raw);
char *dentry_path(const struct dentry *dentry, char *buf, int buflen)
{
- char *p = buf + buflen;
+ DECLARE_BUFFER(b, buf, buflen);
if (unlikely(d_unlinked(dentry)))
- prepend(&p, &buflen, "//deleted", 10);
+ prepend(&b, "//deleted", 10);
else
- prepend(&p, &buflen, "", 1);
- return __dentry_path(dentry, p, buflen);
+ prepend(&b, "", 1);
+ return __dentry_path(dentry, &b);
}
static void get_fs_root_and_pwd_rcu(struct fs_struct *fs, struct path *root,
@@ -386,24 +395,23 @@ SYSCALL_DEFINE2(getcwd, char __user *, buf, unsigned long, size)
error = -ENOENT;
if (!d_unlinked(pwd.dentry)) {
unsigned long len;
- char *cwd = page + PATH_MAX;
- int buflen = PATH_MAX;
+ DECLARE_BUFFER(b, page, PATH_MAX);
- prepend(&cwd, &buflen, "", 1);
- if (prepend_path(&pwd, &root, &cwd, &buflen) > 0)
- prepend(&cwd, &buflen, "(unreachable)", 13);
+ prepend(&b, "", 1);
+ if (prepend_path(&pwd, &root, &b) > 0)
+ prepend(&b, "(unreachable)", 13);
rcu_read_unlock();
- if (buflen < 0) {
+ if (b.len < 0) {
error = -ENAMETOOLONG;
goto out;
}
error = -ERANGE;
- len = PATH_MAX + page - cwd;
+ len = PATH_MAX - b.len;
if (len <= size) {
error = len;
- if (copy_to_user(buf, cwd, len))
+ if (copy_to_user(buf, b.buf, len))
error = -EFAULT;
}
} else {
generated by cgit v1.2.3 (git 2.25.1) at 2024-11-13 07:53:58 +0000