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d_path: lift -ENAMETOOLONG handling into callers of prepend_path()

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The only negative value ever returned by prepend_path() is -ENAMETOOLONG
and callers can recognize that situation (overflow) by looking at the
sign of buflen.  Lift that into the callers; we already have the
same logics (buf if buflen is non-negative, ERR_PTR(-ENAMETOOLONG) otherwise)
in several places and that'll become a new primitive several commits down
the road.

Make prepend_path() return 0 instead of -ENAMETOOLONG.  That makes for
saner calling conventions (0/1/2/3/-ENAMETOOLONG is obnoxious) and
callers actually get simpler, especially once the aforementioned
primitive gets added.

In prepend_path() itself we switch prepending the / (in case of
empty path) to use of prepend() - no need to open-code that, compiler
will do the right thing.  It's exactly the same logics as in
__dentry_path().

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2021-05-17 22:29:03 -04:00
parent d8548232ea
commit 01a4428ee7
1 changed files with 11 additions and 28 deletions
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39
fs/d_path.c
View file

@ -127,8 +127,7 @@ static int prepend_path(const struct path *path,
}
parent = dentry->d_parent;
prefetch(parent);
error = prepend_name(&bptr, &blen, &dentry->d_name);
if (error)
if (unlikely(prepend_name(&bptr, &blen, &dentry->d_name) < 0))
break;
dentry = parent;
@ -149,12 +148,9 @@ static int prepend_path(const struct path *path,
}
done_seqretry(&mount_lock, m_seq);
if (error >= 0 && bptr == *buffer) {
if (--blen < 0)
error = -ENAMETOOLONG;
else
*--bptr = '/';
}
if (blen == *buflen)
prepend(&bptr, &blen, "/", 1);
*buffer = bptr;
*buflen = blen;
return error;
@ -181,16 +177,11 @@ char *__d_path(const struct path *path,
char *buf, int buflen)
{
char *res = buf + buflen;
int error;
prepend(&res, &buflen, "", 1);
error = prepend_path(path, root, &res, &buflen);
if (error < 0)
return ERR_PTR(error);
if (error > 0)
if (prepend_path(path, root, &res, &buflen) > 0)
return NULL;
return res;
return buflen >= 0 ? res : ERR_PTR(-ENAMETOOLONG);
}
char *d_absolute_path(const struct path *path,
@ -198,16 +189,11 @@ char *d_absolute_path(const struct path *path,
{
struct path root = {};
char *res = buf + buflen;
int error;
prepend(&res, &buflen, "", 1);
error = prepend_path(path, &root, &res, &buflen);
if (error > 1)
error = -EINVAL;
if (error < 0)
return ERR_PTR(error);
return res;
if (prepend_path(path, &root, &res, &buflen) > 1)
return ERR_PTR(-EINVAL);
return buflen >= 0 ? res : ERR_PTR(-ENAMETOOLONG);
}
static void get_fs_root_rcu(struct fs_struct *fs, struct path *root)
@ -240,7 +226,6 @@ char *d_path(const struct path *path, char *buf, int buflen)
{
char *res = buf + buflen;
struct path root;
int error;
/*
* We have various synthetic filesystems that never get mounted. On
@ -263,12 +248,10 @@ char *d_path(const struct path *path, char *buf, int buflen)
prepend(&res, &buflen, " (deleted)", 11);
else
prepend(&res, &buflen, "", 1);
error = prepend_path(path, &root, &res, &buflen);
prepend_path(path, &root, &res, &buflen);
rcu_read_unlock();
if (error < 0)
res = ERR_PTR(error);
return res;
return buflen >= 0 ? res : ERR_PTR(-ENAMETOOLONG);
}
EXPORT_SYMBOL(d_path);