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Subject[PATCH RFC 4/4] proc: support flushing dcache entries of a task on multiple procfs mounts
Date
This allows to flush dcache entries of a task on multiple procfs mounts
per pid namespace.

Maybe this patch is nedded since this is just an optimization and maybe
it contains bugs.

Signed-off-by: Djalal Harouni <tixxdz@gmail.com>
---
fs/proc/base.c | 28 ++++++++++++++++++++++------
fs/proc/inode.c | 13 +++++++++++--
fs/proc/root.c | 13 +++++++++++++
include/linux/pid_namespace.h | 42 ++++++++++++++++++++++++++++++++++++++++++
include/linux/proc_fs.h | 5 +++++
5 files changed, 93 insertions(+), 8 deletions(-)

diff --git a/fs/proc/base.c b/fs/proc/base.c
index fd16566..0b96eb1 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -1739,7 +1739,6 @@ int pid_getattr(const struct path *path, struct kstat *stat,
struct task_struct *task;
struct inode *inode = d_inode(path->dentry);
struct proc_fs_info *fs_info = proc_sb(inode->i_sb);
- struct pid_namespace *pid = fs_info->pid_ns;

generic_fillattr(inode, stat);

@@ -2967,7 +2966,8 @@ static const struct inode_operations proc_tgid_base_inode_operations = {
.permission = proc_pid_permission,
};

-static void proc_flush_task_mnt(struct vfsmount *mnt, pid_t pid, pid_t tgid)
+static void proc_flush_task_mnt_root(struct dentry *mnt_root,
+ pid_t pid, pid_t tgid)
{
struct dentry *dentry, *leader, *dir;
char buf[PROC_NUMBUF];
@@ -2976,7 +2976,7 @@ static void proc_flush_task_mnt(struct vfsmount *mnt, pid_t pid, pid_t tgid)
name.name = buf;
name.len = snprintf(buf, sizeof(buf), "%d", pid);
/* no ->d_hash() rejects on procfs */
- dentry = d_hash_and_lookup(mnt->mnt_root, &name);
+ dentry = d_hash_and_lookup(mnt_root, &name);
if (dentry) {
d_invalidate(dentry);
dput(dentry);
@@ -2987,7 +2987,7 @@ static void proc_flush_task_mnt(struct vfsmount *mnt, pid_t pid, pid_t tgid)

name.name = buf;
name.len = snprintf(buf, sizeof(buf), "%d", tgid);
- leader = d_hash_and_lookup(mnt->mnt_root, &name);
+ leader = d_hash_and_lookup(mnt_root, &name);
if (!leader)
goto out;

@@ -3042,14 +3042,30 @@ void proc_flush_task(struct task_struct *task)
int i;
struct pid *pid, *tgid;
struct upid *upid;
+ struct proc_fs_info *fs_info_entry;
+ struct pid_namespace *pid_ns;
+ struct dentry *mnt_root;

pid = task_pid(task);
tgid = task_tgid(task);

for (i = 0; i <= pid->level; i++) {
upid = &pid->numbers[i];
- proc_flush_task_mnt(upid->ns->proc_mnt, upid->nr,
- tgid->numbers[i].nr);
+ pid_ns = upid->ns;
+
+ pidns_procfs_lock_shared(pid_ns);
+ list_for_each_entry(fs_info_entry, &pid_ns->procfs_mounts,
+ pidns_entry) {
+ if (proc_fs_get_unshare(fs_info_entry) == PROC_FS_V2) {
+ mnt_root = fs_info_entry->sb->s_root;
+ proc_flush_task_mnt_root(mnt_root, upid->nr,
+ tgid->numbers[i].nr);
+ }
+ }
+ pidns_procfs_unlock_shared(pid_ns);
+
+ mnt_root = pid_ns->proc_mnt->mnt_root;
+ proc_flush_task_mnt_root(mnt_root, upid->nr, tgid->numbers[i].nr);
}
}

diff --git a/fs/proc/inode.c b/fs/proc/inode.c
index 5f7557d..73e49b3 100644
--- a/fs/proc/inode.c
+++ b/fs/proc/inode.c
@@ -478,10 +478,19 @@ struct inode *proc_get_inode(struct super_block *sb, struct proc_dir_entry *de)
int proc_fill_super(struct super_block *s, void *data, int silent)
{
struct proc_fs_info *fs_info = proc_sb(s);
+ struct pid_namespace *ns = get_pid_ns(fs_info->pid_ns);
struct inode *root_inode;
- int ret;
+ int ret, version;

- get_pid_ns(fs_info->pid_ns);
+ fs_info->sb = s;
+
+ version = proc_fs_get_unshare(fs_info);
+
+ if (version == PROC_FS_V2) {
+ pidns_procfs_lock(ns);
+ list_add_tail(&fs_info->pidns_entry, &ns->procfs_mounts);
+ pidns_procfs_unlock(ns);
+ }

if (!proc_parse_options(data, fs_info))
return -EINVAL;
diff --git a/fs/proc/root.c b/fs/proc/root.c
index 7a8f425..73f972f 100644
--- a/fs/proc/root.c
+++ b/fs/proc/root.c
@@ -222,6 +222,7 @@ static struct dentry *proc_mount(struct file_system_type *fs_type,

static void proc_destroy_sb(struct super_block *sb)
{
+ int version;
struct proc_fs_info *fs_info = proc_sb(sb);
struct pid_namespace *ns = (struct pid_namespace *)fs_info->pid_ns;

@@ -229,6 +230,15 @@ static void proc_destroy_sb(struct super_block *sb)
dput(ns->proc_self);
if (ns->proc_thread_self)
dput(ns->proc_thread_self);
+
+ version = proc_fs_get_unshare(fs_info);
+
+ if (version == PROC_FS_V2) {
+ pidns_procfs_lock(ns);
+ list_del(&fs_info->pidns_entry);
+ pidns_procfs_unlock(ns);
+ }
+
kill_anon_super(sb);
put_pid_ns(ns);
kfree(fs_info);
@@ -352,6 +362,9 @@ int pid_ns_prepare_proc(struct pid_namespace *ns)
return PTR_ERR(mnt);

ns->proc_mnt = mnt;
+ init_rwsem(&ns->rw_procfs_mnts);
+ INIT_LIST_HEAD(&ns->procfs_mounts);
+
return 0;
}

diff --git a/include/linux/pid_namespace.h b/include/linux/pid_namespace.h
index c2a989d..05639c8 100644
--- a/include/linux/pid_namespace.h
+++ b/include/linux/pid_namespace.h
@@ -41,6 +41,8 @@ struct pid_namespace {
struct vfsmount *proc_mnt;
struct dentry *proc_self;
struct dentry *proc_thread_self;
+ struct rw_semaphore rw_procfs_mnts;
+ struct list_head procfs_mounts; /* list of separated procfs mounts */
#endif
#ifdef CONFIG_BSD_PROCESS_ACCT
struct fs_pin *bacct;
@@ -107,4 +109,44 @@ extern struct pid_namespace *task_active_pid_ns(struct task_struct *tsk);
void pidhash_init(void);
void pidmap_init(void);

+#ifdef CONFIG_PROC_FS
+static inline void pidns_procfs_lock(struct pid_namespace *pid_ns)
+{
+ down_write(&pid_ns->rw_procfs_mnts);
+}
+
+static inline void pidns_procfs_unlock(struct pid_namespace *pid_ns)
+{
+ up_write(&pid_ns->rw_procfs_mnts);
+}
+
+static inline void pidns_procfs_lock_shared(struct pid_namespace *pid_ns)
+{
+ down_read(&pid_ns->rw_procfs_mnts);
+}
+
+static inline void pidns_procfs_unlock_shared(struct pid_namespace *pid_ns)
+{
+ up_read(&pid_ns->rw_procfs_mnts);
+}
+#else /* !CONFIG_PROC_FS */
+
+static inline void pidns_procfs_lock(struct pid_namespace *pid_ns)
+{
+}
+
+static inline void pidns_procfs_unlock(struct pid_namespace *pid_ns)
+{
+}
+
+static inline void pidns_procfs_lock_shared(struct pid_namespace *pid_ns)
+{
+}
+
+static inline void pidns_procfs_unlock_shared(struct pid_namespace *pid_ns)
+{
+}
+
+#endif /* CONFIG_PROC_FS */
+
#endif /* _LINUX_PID_NS_H */
diff --git a/include/linux/proc_fs.h b/include/linux/proc_fs.h
index e3a78a5..b2200e3 100644
--- a/include/linux/proc_fs.h
+++ b/include/linux/proc_fs.h
@@ -15,7 +15,12 @@ enum {

struct proc_fs_info {
refcount_t users;
+
+ struct super_block *sb;
struct pid_namespace *pid_ns;
+
+ struct list_head pidns_entry; /* Node in procfs_mounts of a pidns */
+
kgid_t pid_gid;
int hide_pid;
int version;
--
2.10.2
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