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mount_setattr(): clean the control flow and calling conventions

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separate the "cleanup" and "apply" codepaths (they have almost no overlap),
fold the "cleanup" into "prepare" (which eliminates the need of ->revert)
and make loops more idiomatic.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2022-02-28 23:04:20 -05:00
parent 87bb5b6001
commit e257039f0f
1 changed files with 40 additions and 42 deletions
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82
fs/namespace.c
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@ -82,7 +82,6 @@ struct mount_kattr {
unsigned int lookup_flags;
bool recurse;
struct user_namespace *mnt_userns;
struct mount *revert;
};
/* /sys/fs */
@ -4014,32 +4013,39 @@ static inline bool mnt_allow_writers(const struct mount_kattr *kattr,
static int mount_setattr_prepare(struct mount_kattr *kattr, struct mount *mnt)
{
struct mount *m = mnt;
struct mount *m;
int err;
do {
int err = -EPERM;
unsigned int flags;
kattr->revert = m;
flags = recalc_flags(kattr, m);
if (!can_change_locked_flags(m, flags))
return err;
for (m = mnt; m; m = next_mnt(m, mnt)) {
if (!can_change_locked_flags(m, recalc_flags(kattr, m))) {
err = -EPERM;
break;
}
err = can_idmap_mount(kattr, m);
if (err)
return err;
break;
if (mnt_allow_writers(kattr, m))
continue;
if (!mnt_allow_writers(kattr, m)) {
err = mnt_hold_writers(m);
if (err)
break;
}
err = mnt_hold_writers(m);
if (err)
return err;
} while (kattr->recurse && (m = next_mnt(m, mnt)));
if (!kattr->recurse)
return 0;
}
kattr->revert = NULL;
return 0;
if (err) {
struct mount *p;
for (p = mnt; p != m; p = next_mnt(p, mnt)) {
/* If we had to hold writers unblock them. */
if (p->mnt.mnt_flags & MNT_WRITE_HOLD)
mnt_unhold_writers(p);
}
}
return err;
}
static void do_idmap_mount(const struct mount_kattr *kattr, struct mount *mnt)
@ -4067,36 +4073,27 @@ static void do_idmap_mount(const struct mount_kattr *kattr, struct mount *mnt)
put_user_ns(old_mnt_userns);
}
static void mount_setattr_finish(struct mount_kattr *kattr, struct mount *mnt)
static void mount_setattr_commit(struct mount_kattr *kattr, struct mount *mnt)
{
struct mount *m = mnt;
struct mount *m;
do {
if (!kattr->revert) {
unsigned int flags;
for (m = mnt; m; m = next_mnt(m, mnt)) {
unsigned int flags;
do_idmap_mount(kattr, m);
flags = recalc_flags(kattr, m);
WRITE_ONCE(m->mnt.mnt_flags, flags);
}
do_idmap_mount(kattr, m);
flags = recalc_flags(kattr, m);
WRITE_ONCE(m->mnt.mnt_flags, flags);
/* If we had to hold writers unblock them. */
if (m->mnt.mnt_flags & MNT_WRITE_HOLD)
mnt_unhold_writers(m);
if (!kattr->revert && kattr->propagation)
if (kattr->propagation)
change_mnt_propagation(m, kattr->propagation);
/*
* On failure, only cleanup until we found the first mount
* we failed to handle.
*/
if (kattr->revert == m)
return;
} while (kattr->recurse && (m = next_mnt(m, mnt)));
if (!kattr->revert)
touch_mnt_namespace(mnt->mnt_ns);
if (!kattr->recurse)
break;
}
touch_mnt_namespace(mnt->mnt_ns);
}
static int do_mount_setattr(struct path *path, struct mount_kattr *kattr)
@ -4144,7 +4141,8 @@ static int do_mount_setattr(struct path *path, struct mount_kattr *kattr)
* changes and if we failed we clean up.
*/
err = mount_setattr_prepare(kattr, mnt);
mount_setattr_finish(kattr, mnt);
if (!err)
mount_setattr_commit(kattr, mnt);
out:
unlock_mount_hash();