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d_path: saner calling conventions for __dentry_path()

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1) lift NUL-termination into the callers
2) pass pointer to the end of buffer instead of that to beginning.

(1) allows to simplify dentry_path() - we don't need to play silly
games with restoring the leading / of "//deleted" after __dentry_path()
would've overwritten it with NUL.

We also do not need to check if (either) prepend() in there fails -
if the buffer is not large enough, we'll end with negative buflen
after prepend() and __dentry_path() will return the right value
(ERR_PTR(-ENAMETOOLONG)) just fine.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2021-05-17 20:16:51 -04:00
parent dfe5087675
commit 3a291c974c
1 changed files with 12 additions and 19 deletions
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31
fs/d_path.c
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@ -326,22 +326,21 @@ char *simple_dname(struct dentry *dentry, char *buffer, int buflen)
/* /*
* Write full pathname from the root of the filesystem into the buffer. * Write full pathname from the root of the filesystem into the buffer.
*/ */
static char *__dentry_path(const struct dentry *d, char *buf, int buflen) static char *__dentry_path(const struct dentry *d, char *p, int buflen)
{ {
const struct dentry *dentry; const struct dentry *dentry;
char *end, *retval; char *end, *retval;
int len, seq = 0; int len, seq = 0;
int error = 0; int error = 0;
if (buflen < 2) if (buflen < 1)
goto Elong; goto Elong;
rcu_read_lock(); rcu_read_lock();
restart: restart:
dentry = d; dentry = d;
end = buf + buflen; end = p;
len = buflen; len = buflen;
prepend(&end, &len, "", 1);
/* Get '/' right */ /* Get '/' right */
retval = end-1; retval = end-1;
*retval = '/'; *retval = '/';
@ -373,27 +372,21 @@ Elong:
char *dentry_path_raw(const struct dentry *dentry, char *buf, int buflen) char *dentry_path_raw(const struct dentry *dentry, char *buf, int buflen)
{ {
return __dentry_path(dentry, buf, buflen); char *p = buf + buflen;
prepend(&p, &buflen, "", 1);
return __dentry_path(dentry, p, buflen);
} }
EXPORT_SYMBOL(dentry_path_raw); EXPORT_SYMBOL(dentry_path_raw);
char *dentry_path(const struct dentry *dentry, char *buf, int buflen) char *dentry_path(const struct dentry *dentry, char *buf, int buflen)
{ {
char *p = NULL; char *p = buf + buflen;
char *retval;
if (d_unlinked(dentry)) { if (unlikely(d_unlinked(dentry)))
p = buf + buflen; prepend(&p, &buflen, "//deleted", 10);
if (prepend(&p, &buflen, "//deleted", 10) != 0) else
goto Elong; prepend(&p, &buflen, "", 1);
buflen++; return __dentry_path(dentry, p, buflen);
}
retval = __dentry_path(dentry, buf, buflen);
if (!IS_ERR(retval) && p)
*p = '/'; /* restore '/' overriden with '\0' */
return retval;
Elong:
return ERR_PTR(-ENAMETOOLONG);
} }
static void get_fs_root_and_pwd_rcu(struct fs_struct *fs, struct path *root, static void get_fs_root_and_pwd_rcu(struct fs_struct *fs, struct path *root,