On Mon, Jun 23, 2025 at 06:03:15PM +0100, Al Viro wrote:
> I don't know... 7 callers with explicit strlen():
> drivers/gpu/drm/i915/gem/i915_gemfs.c:16: return vfs_parse_fs_string(fc, key, val, strlen(val));
> drivers/gpu/drm/v3d/v3d_gemfs.c:12: return vfs_parse_fs_string(fc, key, val, strlen(val));
> fs/namespace.c:1284: ret = vfs_parse_fs_string(fc, "source",
> fs/namespace.c:3799: err = vfs_parse_fs_string(fc, "subtype",
> fs/namespace.c:3802: err = vfs_parse_fs_string(fc, "source", name, strlen(name));
> fs/nfs/fs_context.c:1230: ret = vfs_parse_fs_string(fc, "context",
> kernel/trace/trace.c:10280: ret = vfs_parse_fs_string(fc, "source",
>
> 3 callers that could as well use strlen(), except that some of them need
> to cope with NULL (using 0 for length in that case):
> fs/fs_context.c:230: ret = vfs_parse_fs_string(fc, key, value, v_len);
> fs/nfs/namespace.c:293: ret = vfs_parse_fs_string(fc, "source", p, buffer + 4096 - p);
> fs/smb/client/fs_context.c:785: ret = vfs_parse_fs_string(fc, key, value, len);
>
> 1 caller that really does need len < strlen(s):
> fs/afs/mntpt.c:140: ret = vfs_parse_fs_string(fc, "source", content, size - 1);
>
> > I just feel that at a minimum you shouldn't implement add_param()
> > twice, because some other users *would* want to do that.
> >
> > So I wish you had made that a real helper - which would obviously then
> > also force a naming change ("fs_context_add_param()".
Frankly, looking at that stuff... I wonder if we should add
vfs_parse_fs_qstr() for "comes with length" variant and lose the length
argument of vfs_parse_fs_string().
Yes, it's a flagday change. Compiler will immediately catch any place
that needs to be converted, and D/f/porting.rst part should be clear
enough.
How about something like the following (completely untested), on top of -rc3?
Objections, anyone?
[PATCH] change the calling conventions for vfs_parse_fs_string()
Absolute majority of callers are passing the 4th argument equal to
strlen() of the 3rd one.
Drop the v_size argument, add vfs_parse_fs_qstr() for the cases that
want independent length.
Signed-off-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
---
diff --git a/Documentation/filesystems/mount_api.rst b/Documentation/filesystems/mount_api.rst
index e149b89118c8..c99ab1f7fea4 100644
--- a/Documentation/filesystems/mount_api.rst
+++ b/Documentation/filesystems/mount_api.rst
@@ -504,10 +504,18 @@ returned.
clear the pointer, but then becomes responsible for disposing of the
object.
+ * ::
+
+ int vfs_parse_fs_qstr(struct fs_context *fc, const char *key,
+ const struct qstr *value);
+
+ A wrapper around vfs_parse_fs_param() that copies the value string it is
+ passed.
+
* ::
int vfs_parse_fs_string(struct fs_context *fc, const char *key,
- const char *value, size_t v_size);
+ const char *value);
A wrapper around vfs_parse_fs_param() that copies the value string it is
passed.
diff --git a/Documentation/filesystems/porting.rst b/Documentation/filesystems/porting.rst
index 3616d7161dab..cbbabdf130a6 100644
--- a/Documentation/filesystems/porting.rst
+++ b/Documentation/filesystems/porting.rst
@@ -1249,3 +1249,13 @@ Using try_lookup_noperm() will require linux/namei.h to be included.
Calling conventions for ->d_automount() have changed; we should *not* grab
an extra reference to new mount - it should be returned with refcount 1.
+
+---
+
+**mandatory**
+
+Calling conventions for vfs_parse_fs_string() have changed; it does *not*
+take length anymore (value ? strlen(value) : 0 is used). If you want
+a different length, use
+ vfs_parse_fs_qstr(fc, key, &QSTR_INIT(value, len))
+instead.
diff --git a/fs/afs/mntpt.c b/fs/afs/mntpt.c
index 9434a5399f2b..33d1bb2b75bf 100644
--- a/fs/afs/mntpt.c
+++ b/fs/afs/mntpt.c
@@ -137,7 +137,8 @@ static int afs_mntpt_set_params(struct fs_context *fc, struct dentry *mntpt)
ret = -EINVAL;
if (content[size - 1] == '.')
- ret = vfs_parse_fs_string(fc, "source", content, size - 1);
+ ret = vfs_parse_fs_qstr(fc, "source",
+ &QSTR_INIT(content, size - 1));
do_delayed_call(&cleanup);
if (ret < 0)
return ret;
diff --git a/fs/fs_context.c b/fs/fs_context.c
index 666e61753aed..93b7ebf8d927 100644
--- a/fs/fs_context.c
+++ b/fs/fs_context.c
@@ -161,25 +161,24 @@ int vfs_parse_fs_param(struct fs_context *fc, struct fs_parameter *param)
EXPORT_SYMBOL(vfs_parse_fs_param);
/**
- * vfs_parse_fs_string - Convenience function to just parse a string.
+ * vfs_parse_fs_qstr - Convenience function to just parse a string.
* @fc: Filesystem context.
* @key: Parameter name.
* @value: Default value.
- * @v_size: Maximum number of bytes in the value.
*/
-int vfs_parse_fs_string(struct fs_context *fc, const char *key,
- const char *value, size_t v_size)
+int vfs_parse_fs_qstr(struct fs_context *fc, const char *key,
+ const struct qstr *value)
{
int ret;
struct fs_parameter param = {
.key = key,
.type = fs_value_is_flag,
- .size = v_size,
+ .size = value ? value->len : 0,
};
if (value) {
- param.string = kmemdup_nul(value, v_size, GFP_KERNEL);
+ param.string = kmemdup_nul(value->name, value->len, GFP_KERNEL);
if (!param.string)
return -ENOMEM;
param.type = fs_value_is_string;
@@ -189,7 +188,7 @@ int vfs_parse_fs_string(struct fs_context *fc, const char *key,
kfree(param.string);
return ret;
}
-EXPORT_SYMBOL(vfs_parse_fs_string);
+EXPORT_SYMBOL(vfs_parse_fs_qstr);
/**
* vfs_parse_monolithic_sep - Parse key[=val][,key[=val]]* mount data
@@ -218,16 +217,14 @@ int vfs_parse_monolithic_sep(struct fs_context *fc, void *data,
while ((key = sep(&options)) != NULL) {
if (*key) {
- size_t v_len = 0;
char *value = strchr(key, '=');
if (value) {
if (unlikely(value == key))
continue;
*value++ = 0;
- v_len = strlen(value);
}
- ret = vfs_parse_fs_string(fc, key, value, v_len);
+ ret = vfs_parse_fs_string(fc, key, value);
if (ret < 0)
break;
}
diff --git a/fs/namespace.c b/fs/namespace.c
index e13d9ab4f564..c5cc8406d24c 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -1312,8 +1312,7 @@ struct vfsmount *vfs_kern_mount(struct file_system_type *type,
return ERR_CAST(fc);
if (name)
- ret = vfs_parse_fs_string(fc, "source",
- name, strlen(name));
+ ret = vfs_parse_fs_string(fc, "source", name);
if (!ret)
ret = parse_monolithic_mount_data(fc, data);
if (!ret)
@@ -3873,10 +3872,9 @@ static int do_new_mount(struct path *path, const char *fstype, int sb_flags,
fc->oldapi = true;
if (subtype)
- err = vfs_parse_fs_string(fc, "subtype",
- subtype, strlen(subtype));
+ err = vfs_parse_fs_string(fc, "subtype", subtype);
if (!err && name)
- err = vfs_parse_fs_string(fc, "source", name, strlen(name));
+ err = vfs_parse_fs_string(fc, "source", name);
if (!err)
err = parse_monolithic_mount_data(fc, data);
if (!err && !mount_capable(fc))
diff --git a/fs/nfs/fs_context.c b/fs/nfs/fs_context.c
index 13f71ca8c974..de1ecb10831b 100644
--- a/fs/nfs/fs_context.c
+++ b/fs/nfs/fs_context.c
@@ -1227,8 +1227,7 @@ static int nfs23_parse_monolithic(struct fs_context *fc,
int ret;
data->context[NFS_MAX_CONTEXT_LEN] = '\0';
- ret = vfs_parse_fs_string(fc, "context",
- data->context, strlen(data->context));
+ ret = vfs_parse_fs_string(fc, "context", data->context);
if (ret < 0)
return ret;
#else
diff --git a/fs/nfs/namespace.c b/fs/nfs/namespace.c
index 7f1ec9c67ff2..2fe97ab57575 100644
--- a/fs/nfs/namespace.c
+++ b/fs/nfs/namespace.c
@@ -290,7 +290,8 @@ int nfs_do_submount(struct fs_context *fc)
nfs_errorf(fc, "NFS: Couldn't determine submount pathname");
ret = PTR_ERR(p);
} else {
- ret = vfs_parse_fs_string(fc, "source", p, buffer + 4096 - p);
+ ret = vfs_parse_fs_qstr(fc, "source",
+ &QSTR_INIT(p, buffer + 4096 - p));
if (!ret)
ret = vfs_get_tree(fc);
}
diff --git a/fs/smb/client/fs_context.c b/fs/smb/client/fs_context.c
index a634a34d4086..e750906c9c49 100644
--- a/fs/smb/client/fs_context.c
+++ b/fs/smb/client/fs_context.c
@@ -773,16 +773,14 @@ static int smb3_fs_context_parse_monolithic(struct fs_context *fc,
}
- len = 0;
value = strchr(key, '=');
if (value) {
if (value == key)
continue;
*value++ = 0;
- len = strlen(value);
}
- ret = vfs_parse_fs_string(fc, key, value, len);
+ ret = vfs_parse_fs_string(fc, key, value);
if (ret < 0)
break;
}
diff --git a/include/linux/fs_context.h b/include/linux/fs_context.h
index a19e4bd32e4d..a735ed23dd9f 100644
--- a/include/linux/fs_context.h
+++ b/include/linux/fs_context.h
@@ -134,8 +134,13 @@ extern struct fs_context *fs_context_for_submount(struct file_system_type *fs_ty
extern struct fs_context *vfs_dup_fs_context(struct fs_context *fc);
extern int vfs_parse_fs_param(struct fs_context *fc, struct fs_parameter *param);
-extern int vfs_parse_fs_string(struct fs_context *fc, const char *key,
- const char *value, size_t v_size);
+extern int vfs_parse_fs_qstr(struct fs_context *fc, const char *key,
+ const struct qstr *value);
+static inline int vfs_parse_fs_string(struct fs_context *fc, const char *key,
+ const char *value)
+{
+ return vfs_parse_fs_qstr(fc, key, value ? &QSTR(value) : NULL);
+}
int vfs_parse_monolithic_sep(struct fs_context *fc, void *data,
char *(*sep)(char **));
extern int generic_parse_monolithic(struct fs_context *fc, void *data);
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 95ae7c4e5835..77ff2608118b 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -10277,8 +10277,7 @@ static struct vfsmount *trace_automount(struct dentry *mntpt, void *ingore)
if (IS_ERR(fc))
return ERR_CAST(fc);
- ret = vfs_parse_fs_string(fc, "source",
- "tracefs", strlen("tracefs"));
+ ret = vfs_parse_fs_string(fc, "source", "tracefs");
if (!ret)
mnt = fc_mount(fc);
else
