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Commit 2d4d4864 authored by Ram Pai's avatar Ram Pai Committed by Al Viro
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[patch 6/7] vfs: mountinfo: add /proc/<pid>/mountinfo 



[mszeredi@suse.cz] rewrite and split big patch into managable chunks

/proc/mounts in its current form lacks important information:

 - propagation state
 - root of mount for bind mounts
 - the st_dev value used within the filesystem
 - identifier for each mount and it's parent

It also suffers from the following problems:

 - not easily extendable
 - ambiguity of mountpoints within a chrooted environment
 - doesn't distinguish between filesystem dependent and independent options
 - doesn't distinguish between per mount and per super block options

This patch introduces /proc/<pid>/mountinfo which attempts to address
all these deficiencies.

Code shared between /proc/<pid>/mounts and /proc/<pid>/mountinfo is
extracted into separate functions.

Thanks to Al Viro for the help in getting the design right.

Signed-off-by: default avatarRam Pai <linuxram@us.ibm.com>
Signed-off-by: default avatarMiklos Szeredi <mszeredi@suse.cz>
Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent a1a2c409

Documentation/filesystems/proc.txt

+32 −0
Original line number Diff line number Diff line
@@ -43,6 +43,7 @@ Table of Contents 
  2.13	/proc/<pid>/oom_score - Display current oom-killer score

  2.14	/proc/<pid>/io - Display the IO accounting fields

  2.15	/proc/<pid>/coredump_filter - Core dump filtering settings

  2.16	/proc/<pid>/mountinfo - Information about mounts



------------------------------------------------------------------------------

Preface
@@ -2348,4 +2349,35 @@ For example: 
  $ echo 0x7 > /proc/self/coredump_filter

  $ ./some_program



2.16	/proc/<pid>/mountinfo - Information about mounts

--------------------------------------------------------



This file contains lines of the form:



36 35 98:0 /mnt1 /mnt2 rw,noatime master:1 - ext3 /dev/root rw,errors=continue

(1)(2)(3)   (4)   (5)      (6)      (7)   (8) (9)   (10)         (11)



(1) mount ID:  unique identifier of the mount (may be reused after umount)

(2) parent ID:  ID of parent (or of self for the top of the mount tree)

(3) major:minor:  value of st_dev for files on filesystem

(4) root:  root of the mount within the filesystem

(5) mount point:  mount point relative to the process's root

(6) mount options:  per mount options

(7) optional fields:  zero or more fields of the form "tag[:value]"

(8) separator:  marks the end of the optional fields

(9) filesystem type:  name of filesystem of the form "type[.subtype]"

(10) mount source:  filesystem specific information or "none"

(11) super options:  per super block options



Parsers should ignore all unrecognised optional fields.  Currently the

possible optional fields are:



shared:X  mount is shared in peer group X

master:X  mount is slave to peer group X

unbindable  mount is unbindable



For more information on mount propagation see:



  Documentation/filesystems/sharedsubtree.txt



------------------------------------------------------------------------------

fs/namespace.c

+96 −23
Original line number Diff line number Diff line
@@ -746,20 +746,30 @@ static void m_stop(struct seq_file *m, void *v) 
	up_read(&namespace_sem);

}



static int show_vfsmnt(struct seq_file *m, void *v)

{

	struct vfsmount *mnt = list_entry(v, struct vfsmount, mnt_list);

	int err = 0;

	static struct proc_fs_info {

struct proc_fs_info {

	int flag;

		char *str;

	} fs_info[] = {

	const char *str;

};



static void show_sb_opts(struct seq_file *m, struct super_block *sb)

{

	static const struct proc_fs_info fs_info[] = {

		{ MS_SYNCHRONOUS, ",sync" },

		{ MS_DIRSYNC, ",dirsync" },

		{ MS_MANDLOCK, ",mand" },

		{ 0, NULL }

	};

	static struct proc_fs_info mnt_info[] = {

	const struct proc_fs_info *fs_infop;



	for (fs_infop = fs_info; fs_infop->flag; fs_infop++) {

		if (sb->s_flags & fs_infop->flag)

			seq_puts(m, fs_infop->str);

	}

}



static void show_mnt_opts(struct seq_file *m, struct vfsmount *mnt)

{

	static const struct proc_fs_info mnt_info[] = {

		{ MNT_NOSUID, ",nosuid" },

		{ MNT_NODEV, ",nodev" },

		{ MNT_NOEXEC, ",noexec" },
@@ -768,27 +778,37 @@ static int show_vfsmnt(struct seq_file *m, void *v) 
		{ MNT_RELATIME, ",relatime" },

		{ 0, NULL }

	};

	struct proc_fs_info *fs_infop;

	const struct proc_fs_info *fs_infop;



	for (fs_infop = mnt_info; fs_infop->flag; fs_infop++) {

		if (mnt->mnt_flags & fs_infop->flag)

			seq_puts(m, fs_infop->str);

	}

}



static void show_type(struct seq_file *m, struct super_block *sb)

{

	mangle(m, sb->s_type->name);

	if (sb->s_subtype && sb->s_subtype[0]) {

		seq_putc(m, '.');

		mangle(m, sb->s_subtype);

	}

}



static int show_vfsmnt(struct seq_file *m, void *v)

{

	struct vfsmount *mnt = list_entry(v, struct vfsmount, mnt_list);

	int err = 0;

	struct path mnt_path = { .dentry = mnt->mnt_root, .mnt = mnt };



	mangle(m, mnt->mnt_devname ? mnt->mnt_devname : "none");

	seq_putc(m, ' ');

	seq_path(m, &mnt_path, " \t\n\\");

	seq_putc(m, ' ');

	mangle(m, mnt->mnt_sb->s_type->name);

	if (mnt->mnt_sb->s_subtype && mnt->mnt_sb->s_subtype[0]) {

		seq_putc(m, '.');

		mangle(m, mnt->mnt_sb->s_subtype);

	}

	show_type(m, mnt->mnt_sb);

	seq_puts(m, __mnt_is_readonly(mnt) ? " ro" : " rw");

	for (fs_infop = fs_info; fs_infop->flag; fs_infop++) {

		if (mnt->mnt_sb->s_flags & fs_infop->flag)

			seq_puts(m, fs_infop->str);

	}

	for (fs_infop = mnt_info; fs_infop->flag; fs_infop++) {

		if (mnt->mnt_flags & fs_infop->flag)

			seq_puts(m, fs_infop->str);

	}

	show_sb_opts(m, mnt->mnt_sb);

	show_mnt_opts(m, mnt);

	if (mnt->mnt_sb->s_op->show_options)

		err = mnt->mnt_sb->s_op->show_options(m, mnt);

	seq_puts(m, " 0 0\n");
@@ -802,6 +822,59 @@ const struct seq_operations mounts_op = { 
	.show	= show_vfsmnt

};



static int show_mountinfo(struct seq_file *m, void *v)

{

	struct proc_mounts *p = m->private;

	struct vfsmount *mnt = list_entry(v, struct vfsmount, mnt_list);

	struct super_block *sb = mnt->mnt_sb;

	struct path mnt_path = { .dentry = mnt->mnt_root, .mnt = mnt };

	struct path root = p->root;

	int err = 0;



	seq_printf(m, "%i %i %u:%u ", mnt->mnt_id, mnt->mnt_parent->mnt_id,

		   MAJOR(sb->s_dev), MINOR(sb->s_dev));

	seq_dentry(m, mnt->mnt_root, " \t\n\\");

	seq_putc(m, ' ');

	seq_path_root(m, &mnt_path, &root, " \t\n\\");

	if (root.mnt != p->root.mnt || root.dentry != p->root.dentry) {

		/*

		 * Mountpoint is outside root, discard that one.  Ugly,

		 * but less so than trying to do that in iterator in a

		 * race-free way (due to renames).

		 */

		return SEQ_SKIP;

	}

	seq_puts(m, mnt->mnt_flags & MNT_READONLY ? " ro" : " rw");

	show_mnt_opts(m, mnt);



	/* Tagged fields ("foo:X" or "bar") */

	if (IS_MNT_SHARED(mnt))

		seq_printf(m, " shared:%i", mnt->mnt_group_id);

	if (IS_MNT_SLAVE(mnt))

		seq_printf(m, " master:%i", mnt->mnt_master->mnt_group_id);

	if (IS_MNT_UNBINDABLE(mnt))

		seq_puts(m, " unbindable");



	/* Filesystem specific data */

	seq_puts(m, " - ");

	show_type(m, sb);

	seq_putc(m, ' ');

	mangle(m, mnt->mnt_devname ? mnt->mnt_devname : "none");

	seq_puts(m, sb->s_flags & MS_RDONLY ? " ro" : " rw");

	show_sb_opts(m, sb);

	if (sb->s_op->show_options)

		err = sb->s_op->show_options(m, mnt);

	seq_putc(m, '\n');

	return err;

}



const struct seq_operations mountinfo_op = {

	.start	= m_start,

	.next	= m_next,

	.stop	= m_stop,

	.show	= show_mountinfo,

};



static int show_vfsstat(struct seq_file *m, void *v)

{

	struct vfsmount *mnt = list_entry(v, struct vfsmount, mnt_list);
@@ -822,7 +895,7 @@ static int show_vfsstat(struct seq_file *m, void *v) 


	/* file system type */

	seq_puts(m, "with fstype ");

	mangle(m, mnt->mnt_sb->s_type->name);

	show_type(m, mnt->mnt_sb);



	/* optional statistics */

	if (mnt->mnt_sb->s_op->show_stats) {

fs/proc/base.c

+15 −0
Original line number Diff line number Diff line
@@ -604,6 +604,19 @@ static const struct file_operations proc_mounts_operations = { 
	.poll		= mounts_poll,

};



static int mountinfo_open(struct inode *inode, struct file *file)

{

	return mounts_open_common(inode, file, &mountinfo_op);

}



static const struct file_operations proc_mountinfo_operations = {

	.open		= mountinfo_open,

	.read		= seq_read,

	.llseek		= seq_lseek,

	.release	= mounts_release,

	.poll		= mounts_poll,

};



static int mountstats_open(struct inode *inode, struct file *file)

{

	return mounts_open_common(inode, file, &mountstats_op);
@@ -2303,6 +2316,7 @@ static const struct pid_entry tgid_base_stuff[] = { 
	LNK("root",       root),

	LNK("exe",        exe),

	REG("mounts",     S_IRUGO, mounts),

	REG("mountinfo",  S_IRUGO, mountinfo),

	REG("mountstats", S_IRUSR, mountstats),

#ifdef CONFIG_PROC_PAGE_MONITOR

	REG("clear_refs", S_IWUSR, clear_refs),
@@ -2635,6 +2649,7 @@ static const struct pid_entry tid_base_stuff[] = { 
	LNK("root",      root),

	LNK("exe",       exe),

	REG("mounts",    S_IRUGO, mounts),

	REG("mountinfo",  S_IRUGO, mountinfo),

#ifdef CONFIG_PROC_PAGE_MONITOR

	REG("clear_refs", S_IWUSR, clear_refs),

	REG("smaps",     S_IRUGO, smaps),

include/linux/mnt_namespace.h

+1 −0
Original line number Diff line number Diff line
@@ -46,6 +46,7 @@ static inline void get_mnt_ns(struct mnt_namespace *ns) 
}



extern const struct seq_operations mounts_op;

extern const struct seq_operations mountinfo_op;

extern const struct seq_operations mountstats_op;



#endif