Quoting Eric W. Biederman ([email protected]): > > /proc/thread-self is derived from /proc/self. /proc/thread-self > points to the directory in proc containing information about the > current thread. > > This funtionality has been missing for a long time, and is tricky to > implement in userspace as gettid() is not exported by glibc. More > importantly this allows fixing defects in /proc/mounts and /proc/net > where in a threaded application today they wind up being empty files > when only the initial pthread has exited, causing problems for other > threads. > > Signed-off-by: "Eric W. Biederman" <[email protected]>
Hi Eric, I've not had a chance to test these, but apart from two trivial comments below these look good to me, and I appreciate the feature. So with the two fixes (if needed), Acked-by: Serge Hallyn <[email protected]> > --- > fs/proc/Makefile | 1 + > fs/proc/base.c | 15 +++++--- > fs/proc/inode.c | 7 +++- > fs/proc/internal.h | 6 +++ > fs/proc/root.c | 3 ++ > fs/proc/thread_self.c | 85 > +++++++++++++++++++++++++++++++++++++++++++ > include/linux/pid_namespace.h | 1 + > 7 files changed, 112 insertions(+), 6 deletions(-) > create mode 100644 fs/proc/thread_self.c > > diff --git a/fs/proc/Makefile b/fs/proc/Makefile > index 239493ec718e..7151ea428041 100644 > --- a/fs/proc/Makefile > +++ b/fs/proc/Makefile > @@ -23,6 +23,7 @@ proc-y += version.o > proc-y += softirqs.o > proc-y += namespaces.o > proc-y += self.o > +proc-y += thread_self.o > proc-$(CONFIG_PROC_SYSCTL) += proc_sysctl.o > proc-$(CONFIG_NET) += proc_net.o > proc-$(CONFIG_PROC_KCORE) += kcore.o > diff --git a/fs/proc/base.c b/fs/proc/base.c > index ed34e405c6b9..0131156ce7c9 100644 > --- a/fs/proc/base.c > +++ b/fs/proc/base.c > @@ -2847,7 +2847,7 @@ retry: > return iter; > } > > -#define TGID_OFFSET (FIRST_PROCESS_ENTRY + 1) > +#define TGID_OFFSET (FIRST_PROCESS_ENTRY + 2) > > /* for the /proc/ directory itself, after non-process stuff has been done */ > int proc_pid_readdir(struct file *file, struct dir_context *ctx) > @@ -2859,14 +2859,19 @@ int proc_pid_readdir(struct file *file, struct > dir_context *ctx) > if (pos >= PID_MAX_LIMIT + TGID_OFFSET) > return 0; > > - if (pos == TGID_OFFSET - 1) { > + if (pos == TGID_OFFSET - 2) { > struct inode *inode = ns->proc_self->d_inode; > if (!dir_emit(ctx, "self", 4, inode->i_ino, DT_LNK)) > return 0; > - iter.tgid = 0; > - } else { > - iter.tgid = pos - TGID_OFFSET; > + ctx->pos = pos = pos + 1; > + } > + if (pos == TGID_OFFSET - 1) { > + struct inode *inode = ns->proc_thread_self->d_inode; > + if (!dir_emit(ctx, "thread-self", 11, inode->i_ino, DT_LNK)) > + return 0; > + ctx->pos = pos = pos + 1; > } > + iter.tgid = pos - TGID_OFFSET; > iter.task = NULL; > for (iter = next_tgid(ns, iter); > iter.task; > diff --git a/fs/proc/inode.c b/fs/proc/inode.c > index 0adbc02d60e3..333080d7a671 100644 > --- a/fs/proc/inode.c > +++ b/fs/proc/inode.c > @@ -442,6 +442,7 @@ struct inode *proc_get_inode(struct super_block *sb, > struct proc_dir_entry *de) > int proc_fill_super(struct super_block *s) > { > struct inode *root_inode; > + int ret; > > s->s_flags |= MS_NODIRATIME | MS_NOSUID | MS_NOEXEC; > s->s_blocksize = 1024; > @@ -463,5 +464,9 @@ int proc_fill_super(struct super_block *s) > return -ENOMEM; > } > > - return proc_setup_self(s); > + ret = proc_setup_self(s); > + if (ret) { > + return ret; > + } > + return proc_setup_thread_self(s); > } > diff --git a/fs/proc/internal.h b/fs/proc/internal.h > index 3ab6d14e71c5..ee04619173b2 100644 > --- a/fs/proc/internal.h > +++ b/fs/proc/internal.h > @@ -234,6 +234,12 @@ static inline int proc_net_init(void) { return 0; } > extern int proc_setup_self(struct super_block *); > > /* > + * proc_thread_self.c > + */ > +extern int proc_setup_thread_self(struct super_block *); > +extern void proc_thread_self_init(void); > + > +/* > * proc_sysctl.c > */ > #ifdef CONFIG_PROC_SYSCTL > diff --git a/fs/proc/root.c b/fs/proc/root.c > index 5dbadecb234d..48f1c03bc7ed 100644 > --- a/fs/proc/root.c > +++ b/fs/proc/root.c > @@ -149,6 +149,8 @@ static void proc_kill_sb(struct super_block *sb) > ns = (struct pid_namespace *)sb->s_fs_info; > if (ns->proc_self) > dput(ns->proc_self); > + if (ns->proc_thread_self) > + dput(ns->proc_thread_self); > kill_anon_super(sb); > put_pid_ns(ns); > } > @@ -170,6 +172,7 @@ void __init proc_root_init(void) > return; > > proc_self_init(); > + proc_thread_self_init(); > proc_symlink("mounts", NULL, "self/mounts"); > > proc_net_init(); > diff --git a/fs/proc/thread_self.c b/fs/proc/thread_self.c > new file mode 100644 > index 000000000000..59075b509df3 > --- /dev/null > +++ b/fs/proc/thread_self.c > @@ -0,0 +1,85 @@ > +#include <linux/sched.h> > +#include <linux/namei.h> > +#include <linux/slab.h> > +#include <linux/pid_namespace.h> > +#include "internal.h" > + > +/* > + * /proc/thread_self: > + */ > +static int proc_thread_self_readlink(struct dentry *dentry, char __user > *buffer, > + int buflen) > +{ > + struct pid_namespace *ns = dentry->d_sb->s_fs_info; > + pid_t tgid = task_tgid_nr_ns(current, ns); > + pid_t pid = task_pid_nr_ns(current, ns); > + char tmp[PROC_NUMBUF + 6 + PROC_NUMBUF]; In the extreme case you're not adding space for a \0 ? (Unless PROC_NUMBUF includes that) > + if (!pid) > + return -ENOENT; > + sprintf(tmp, "%d/task/%d", tgid, pid); > + return readlink_copy(buffer, buflen, tmp); > +} > + > +static void *proc_thread_self_follow_link(struct dentry *dentry, struct > nameidata *nd) > +{ > + struct pid_namespace *ns = dentry->d_sb->s_fs_info; > + pid_t tgid = task_tgid_nr_ns(current, ns); > + pid_t pid = task_pid_nr_ns(current, ns); > + char *name = ERR_PTR(-ENOENT); > + if (pid) { > + name = kmalloc(PROC_NUMBUF + 6 + PROC_NUMBUF, GFP_KERNEL); Same here. > + if (!name) > + name = ERR_PTR(-ENOMEM); > + else > + sprintf(name, "%d/task/%d", tgid, pid); > + } > + nd_set_link(nd, name); > + return NULL; > +} > + > +static const struct inode_operations proc_thread_self_inode_operations = { > + .readlink = proc_thread_self_readlink, > + .follow_link = proc_thread_self_follow_link, > + .put_link = kfree_put_link, > +}; > + > +static unsigned thread_self_inum; > + > +int proc_setup_thread_self(struct super_block *s) > +{ > + struct inode *root_inode = s->s_root->d_inode; > + struct pid_namespace *ns = s->s_fs_info; > + struct dentry *thread_self; > + > + mutex_lock(&root_inode->i_mutex); > + thread_self = d_alloc_name(s->s_root, "thread-self"); > + if (thread_self) { > + struct inode *inode = new_inode_pseudo(s); > + if (inode) { > + inode->i_ino = thread_self_inum; > + inode->i_mtime = inode->i_atime = inode->i_ctime = > CURRENT_TIME; > + inode->i_mode = S_IFLNK | S_IRWXUGO; > + inode->i_uid = GLOBAL_ROOT_UID; > + inode->i_gid = GLOBAL_ROOT_GID; > + inode->i_op = &proc_thread_self_inode_operations; > + d_add(thread_self, inode); > + } else { > + dput(thread_self); > + thread_self = ERR_PTR(-ENOMEM); > + } > + } else { > + thread_self = ERR_PTR(-ENOMEM); > + } > + mutex_unlock(&root_inode->i_mutex); > + if (IS_ERR(thread_self)) { > + pr_err("proc_fill_super: can't allocate /proc/thread_self\n"); > + return PTR_ERR(thread_self); > + } > + ns->proc_thread_self = thread_self; > + return 0; > +} > + > +void __init proc_thread_self_init(void) > +{ > + proc_alloc_inum(&thread_self_inum); > +} > diff --git a/include/linux/pid_namespace.h b/include/linux/pid_namespace.h > index 7246ef3d4455..1997ffc295a7 100644 > --- a/include/linux/pid_namespace.h > +++ b/include/linux/pid_namespace.h > @@ -33,6 +33,7 @@ struct pid_namespace { > #ifdef CONFIG_PROC_FS > struct vfsmount *proc_mnt; > struct dentry *proc_self; > + struct dentry *proc_thread_self; > #endif > #ifdef CONFIG_BSD_PROCESS_ACCT > struct bsd_acct_struct *bacct; > -- > 1.9.1 > > _______________________________________________ > Containers mailing list > [email protected] > https://lists.linuxfoundation.org/mailman/listinfo/containers -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
