[Devel] [PATCH vz8 1/3] Revert "ms/proc/mounts: add cursor"
Konstantin Khorenko
khorenko at virtuozzo.com
Fri Jul 9 15:26:25 MSK 2021
This reverts commit 2e01d45a2a2dbfa302b387584474645172b7c5bd.
There is another version of this patch in vz7 3.10.0-1160.15.2.vz7.173.8
kernel, so we revert the current (old and wrong) one, will cherry-pick
v2 in following patch.
Signed-off-by: Konstantin Khorenko <khorenko at virtuozzo.com>
---
fs/mount.h | 14 ++-----
fs/namespace.c | 92 ++++++++-----------------------------------
fs/proc_namespace.c | 4 +-
fs/sync.c | 5 ---
include/linux/mount.h | 4 +-
5 files changed, 22 insertions(+), 97 deletions(-)
diff --git a/fs/mount.h b/fs/mount.h
index 66b863fa3db0..9225fc7bce30 100644
--- a/fs/mount.h
+++ b/fs/mount.h
@@ -9,13 +9,7 @@ struct mnt_namespace {
atomic_t count;
struct ns_common ns;
struct mount * root;
- /*
- * Traversal and modification of .list is protected by either
- * - taking namespace_sem for write, OR
- * - taking namespace_sem for read AND taking .ns_lock.
- */
struct list_head list;
- spinlock_t ns_lock;
struct user_namespace *user_ns;
struct ucounts *ucounts;
u64 seq; /* Sequence number to prevent loops */
@@ -143,13 +137,12 @@ struct proc_mounts {
struct mnt_namespace *ns;
struct path root;
int (*show)(struct seq_file *, struct vfsmount *);
- struct mount cursor;
+ void *cached_mount;
+ u64 cached_event;
+ loff_t cached_index;
};
extern const struct seq_operations mounts_op;
-extern inline void lock_ns_list(struct mnt_namespace *ns);
-extern inline void unlock_ns_list(struct mnt_namespace *ns);
-extern inline bool mnt_is_cursor(struct mount *mnt);
extern bool __is_local_mountpoint(struct dentry *dentry);
static inline bool is_local_mountpoint(struct dentry *dentry)
@@ -164,4 +157,3 @@ static inline bool is_anon_ns(struct mnt_namespace *ns)
{
return ns->seq == 0;
}
-extern void mnt_cursor_del(struct mnt_namespace *ns, struct mount *cursor);
diff --git a/fs/namespace.c b/fs/namespace.c
index 321a79198aac..cdeb83740de5 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -671,21 +671,6 @@ struct vfsmount *lookup_mnt(const struct path *path)
return m;
}
-inline void lock_ns_list(struct mnt_namespace *ns)
-{
- spin_lock(&ns->ns_lock);
-}
-
-inline void unlock_ns_list(struct mnt_namespace *ns)
-{
- spin_unlock(&ns->ns_lock);
-}
-
-inline bool mnt_is_cursor(struct mount *mnt)
-{
- return mnt->mnt.mnt_flags & MNT_CURSOR;
-}
-
/*
* __is_local_mountpoint - Test to see if dentry is a mountpoint in the
* current mount namespace.
@@ -711,15 +696,11 @@ bool __is_local_mountpoint(struct dentry *dentry)
goto out;
down_read(&namespace_sem);
- lock_ns_list(ns);
list_for_each_entry(mnt, &ns->list, mnt_list) {
- if (mnt_is_cursor(mnt))
- continue;
is_covered = (mnt->mnt_mountpoint == dentry);
if (is_covered)
break;
}
- unlock_ns_list(ns);
up_read(&namespace_sem);
out:
return is_covered;
@@ -1299,70 +1280,46 @@ struct vfsmount *mnt_clone_internal(const struct path *path)
}
#ifdef CONFIG_PROC_FS
-static struct mount *mnt_list_next(struct mnt_namespace *ns,
- struct list_head *p)
-{
- struct mount *mnt, *ret = NULL;
-
- lock_ns_list(ns);
- list_for_each_continue(p, &ns->list) {
- mnt = list_entry(p, typeof(*mnt), mnt_list);
- if (!mnt_is_cursor(mnt)) {
- ret = mnt;
- break;
- }
- }
- unlock_ns_list(ns);
-
- return ret;
-}
-
/* iterator; we want it to have access to namespace_sem, thus here... */
static void *m_start(struct seq_file *m, loff_t *pos)
{
struct proc_mounts *p = m->private;
- struct list_head *prev;
down_read(&namespace_sem);
- if (!*pos) {
- prev = &p->ns->list;
- } else {
- prev = &p->cursor.mnt_list;
-
- /* Read after we'd reached the end? */
- if (list_empty(prev))
- return NULL;
+ if (p->cached_event == p->ns->event) {
+ void *v = p->cached_mount;
+ if (*pos == p->cached_index)
+ return v;
+ if (*pos == p->cached_index + 1) {
+ v = seq_list_next(v, &p->ns->list, &p->cached_index);
+ return p->cached_mount = v;
+ }
}
- return mnt_list_next(p->ns, prev);
+
+ p->cached_event = p->ns->event;
+ p->cached_mount = seq_list_start(&p->ns->list, *pos);
+ p->cached_index = *pos;
+ return p->cached_mount;
}
static void *m_next(struct seq_file *m, void *v, loff_t *pos)
{
struct proc_mounts *p = m->private;
- struct mount *mnt = v;
- ++*pos;
- return mnt_list_next(p->ns, &mnt->mnt_list);
+ p->cached_mount = seq_list_next(v, &p->ns->list, pos);
+ p->cached_index = *pos;
+ return p->cached_mount;
}
static void m_stop(struct seq_file *m, void *v)
{
- struct proc_mounts *p = m->private;
- struct mount *mnt = v;
-
- lock_ns_list(p->ns);
- if (mnt)
- list_move_tail(&p->cursor.mnt_list, &mnt->mnt_list);
- else
- list_del_init(&p->cursor.mnt_list);
- unlock_ns_list(p->ns);
up_read(&namespace_sem);
}
static int m_show(struct seq_file *m, void *v)
{
struct proc_mounts *p = m->private;
- struct mount *r = v;
+ struct mount *r = list_entry(v, struct mount, mnt_list);
return p->show(m, &r->mnt);
}
@@ -1372,15 +1329,6 @@ const struct seq_operations mounts_op = {
.stop = m_stop,
.show = m_show,
};
-
-void mnt_cursor_del(struct mnt_namespace *ns, struct mount *cursor)
-{
- down_read(&namespace_sem);
- lock_ns_list(ns);
- list_del(&cursor->mnt_list);
- unlock_ns_list(ns);
- up_read(&namespace_sem);
-}
#endif /* CONFIG_PROC_FS */
/**
@@ -3363,7 +3311,6 @@ static struct mnt_namespace *alloc_mnt_ns(struct user_namespace *user_ns, bool a
INIT_LIST_HEAD(&new_ns->list);
INIT_LIST_HEAD(&new_ns->mntns_list);
init_waitqueue_head(&new_ns->poll);
- spin_lock_init(&new_ns->ns_lock);
new_ns->user_ns = get_user_ns(user_ns);
new_ns->ucounts = ucounts;
return new_ns;
@@ -3876,14 +3823,10 @@ static bool mnt_already_visible(struct mnt_namespace *ns, struct vfsmount *new,
bool visible = false;
down_read(&namespace_sem);
- lock_ns_list(ns);
list_for_each_entry(mnt, &ns->list, mnt_list) {
struct mount *child;
int mnt_flags;
- if (mnt_is_cursor(mnt))
- continue;
-
if (mnt->mnt.mnt_sb->s_type != new->mnt_sb->s_type)
continue;
@@ -3931,7 +3874,6 @@ static bool mnt_already_visible(struct mnt_namespace *ns, struct vfsmount *new,
next: ;
}
found:
- unlock_ns_list(ns);
up_read(&namespace_sem);
return visible;
}
diff --git a/fs/proc_namespace.c b/fs/proc_namespace.c
index 969f9c8fbdc0..e16fb8f2049e 100644
--- a/fs/proc_namespace.c
+++ b/fs/proc_namespace.c
@@ -279,8 +279,7 @@ static int mounts_open_common(struct inode *inode, struct file *file,
p->ns = ns;
p->root = root;
p->show = show;
- INIT_LIST_HEAD(&p->cursor.mnt_list);
- p->cursor.mnt.mnt_flags = MNT_CURSOR;
+ p->cached_event = ~0ULL;
return 0;
@@ -297,7 +296,6 @@ static int mounts_release(struct inode *inode, struct file *file)
struct seq_file *m = file->private_data;
struct proc_mounts *p = m->private;
path_put(&p->root);
- mnt_cursor_del(p->ns, &p->cursor);
put_mnt_ns(p->ns);
return seq_release_private(inode, file);
}
diff --git a/fs/sync.c b/fs/sync.c
index 75a1e019ee7c..ef4b1d17fe5a 100644
--- a/fs/sync.c
+++ b/fs/sync.c
@@ -134,11 +134,7 @@ static int sync_collect_filesystems(struct ve_struct *ve, struct list_head *sync
BUG_ON(!list_empty(sync_list));
down_read(&namespace_sem);
- lock_ns_list(mnt_ns);
list_for_each_entry(mnt, &mnt_ns->list, mnt_list) {
- if (mnt_is_cursor(mnt))
- continue;
-
if (sync_filesystem_collected(sync_list, mnt->mnt.mnt_sb))
continue;
@@ -158,7 +154,6 @@ static int sync_collect_filesystems(struct ve_struct *ve, struct list_head *sync
spin_unlock(&sb_lock);
list_add_tail(&ss->list, sync_list);
}
- unlock_ns_list(mnt_ns);
up_read(&namespace_sem);
return ret;
}
diff --git a/include/linux/mount.h b/include/linux/mount.h
index 5316b60e9028..45b1f56c6c2f 100644
--- a/include/linux/mount.h
+++ b/include/linux/mount.h
@@ -49,8 +49,7 @@ struct mnt_namespace;
#define MNT_ATIME_MASK (MNT_NOATIME | MNT_NODIRATIME | MNT_RELATIME )
#define MNT_INTERNAL_FLAGS (MNT_SHARED | MNT_WRITE_HOLD | MNT_INTERNAL | \
- MNT_DOOMED | MNT_SYNC_UMOUNT | MNT_MARKED | \
- MNT_CURSOR)
+ MNT_DOOMED | MNT_SYNC_UMOUNT | MNT_MARKED)
#define MNT_INTERNAL 0x4000
@@ -64,7 +63,6 @@ struct mnt_namespace;
#define MNT_SYNC_UMOUNT 0x2000000
#define MNT_MARKED 0x4000000
#define MNT_UMOUNT 0x8000000
-#define MNT_CURSOR 0x10000000
struct vfsmount {
struct dentry *mnt_root; /* root of the mounted tree */
--
2.28.0
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