[PATCH v2 2/3] namei: Standardize callers of filename_lookup()

From: Stephen Brennan
Date: Tue Sep 07 2021 - 16:51:07 EST


filename_lookup() has two variants, one which drops the caller's
reference to filename (filename_lookup), and one which does
not (__filename_lookup). This can be confusing as it's unusual to drop a
caller's reference. Remove filename_lookup, rename __filename_lookup
to filename_lookup, and convert all callers. The cost is a few slightly
longer functions, but the clarity is greater.

Link: https://lore.kernel.org/linux-fsdevel/YS+dstZ3xfcLxhoB@xxxxxxxxxxxxxxxxxxxxx/
Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Stephen Brennan <stephen.s.brennan@xxxxxxxxxx>
---
fs/fs_parser.c | 1 -
fs/namei.c | 41 ++++++++++++++++++++++++-----------------
2 files changed, 24 insertions(+), 18 deletions(-)

diff --git a/fs/fs_parser.c b/fs/fs_parser.c
index 980d44fd3a36..3df07c0e32b3 100644
--- a/fs/fs_parser.c
+++ b/fs/fs_parser.c
@@ -165,7 +165,6 @@ int fs_lookup_param(struct fs_context *fc,
return invalf(fc, "%s: not usable as path", param->key);
}

- f->refcnt++; /* filename_lookup() drops our ref. */
ret = filename_lookup(param->dirfd, f, flags, _path, NULL);
if (ret < 0) {
errorf(fc, "%s: Lookup failure for '%s'", param->key, f->name);
diff --git a/fs/namei.c b/fs/namei.c
index f2af301cc79f..76871b7f127a 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -2467,7 +2467,7 @@ static int path_lookupat(struct nameidata *nd, unsigned flags, struct path *path
return err;
}

-static int __filename_lookup(int dfd, struct filename *name, unsigned flags,
+int filename_lookup(int dfd, struct filename *name, unsigned flags,
struct path *path, struct path *root)
{
int retval;
@@ -2488,15 +2488,6 @@ static int __filename_lookup(int dfd, struct filename *name, unsigned flags,
return retval;
}

-int filename_lookup(int dfd, struct filename *name, unsigned flags,
- struct path *path, struct path *root)
-{
- int retval = __filename_lookup(dfd, name, flags, path, root);
-
- putname(name);
- return retval;
-}
-
/* Returns 0 and nd will be valid on success; Retuns error, otherwise. */
static int path_parentat(struct nameidata *nd, unsigned flags,
struct path *parent)
@@ -2571,8 +2562,14 @@ struct dentry *kern_path_locked(const char *name, struct path *path)

int kern_path(const char *name, unsigned int flags, struct path *path)
{
- return filename_lookup(AT_FDCWD, getname_kernel(name),
- flags, path, NULL);
+ struct filename *filename;
+ int ret;
+
+ filename = getname_kernel(name);
+ ret = filename_lookup(AT_FDCWD, filename, flags, path, NULL);
+ putname(filename);
+ return ret;
+
}
EXPORT_SYMBOL(kern_path);

@@ -2588,10 +2585,15 @@ int vfs_path_lookup(struct dentry *dentry, struct vfsmount *mnt,
const char *name, unsigned int flags,
struct path *path)
{
+ struct filename *filename;
struct path root = {.mnt = mnt, .dentry = dentry};
+ int ret;
+
+ filename = getname_kernel(name);
/* the first argument of filename_lookup() is ignored with root */
- return filename_lookup(AT_FDCWD, getname_kernel(name),
- flags , path, &root);
+ ret = filename_lookup(AT_FDCWD, filename, flags, path, &root);
+ putname(filename);
+ return ret;
}
EXPORT_SYMBOL(vfs_path_lookup);

@@ -2795,8 +2797,13 @@ int path_pts(struct path *path)
int user_path_at_empty(int dfd, const char __user *name, unsigned flags,
struct path *path, int *empty)
{
- return filename_lookup(dfd, getname_flags(name, flags, empty),
- flags, path, NULL);
+ struct filename *filename;
+ int ret;
+
+ filename = getname_flags(name, flags, empty);
+ ret = filename_lookup(dfd, filename, flags, path, NULL);
+ putname(filename);
+ return ret;
}
EXPORT_SYMBOL(user_path_at_empty);

@@ -4421,7 +4428,7 @@ int do_linkat(int olddfd, struct filename *old, int newdfd,
if (flags & AT_SYMLINK_FOLLOW)
how |= LOOKUP_FOLLOW;
retry:
- error = __filename_lookup(olddfd, old, how, &old_path, NULL);
+ error = filename_lookup(olddfd, old, how, &old_path, NULL);
if (error)
goto out_putnames;

--
2.30.2