From: Ram Pai [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//mountinfo which attempts to address all these deficiencies. Code shared between /proc//mounts and /proc//mountinfo is extracted into separate functions. Thanks to Al Viro for the help in getting the design right. Signed-off-by: Ram Pai Signed-off-by: Miklos Szeredi --- Documentation/filesystems/proc.txt | 33 ++++++++++ fs/namespace.c | 121 +++++++++++++++++++++++++++++-------- fs/proc/base.c | 15 ++++ include/linux/mnt_namespace.h | 1 4 files changed, 147 insertions(+), 23 deletions(-) Index: vfs-2.6/Documentation/filesystems/proc.txt =================================================================== --- vfs-2.6.orig/Documentation/filesystems/proc.txt 2008-03-26 21:37:52.000000000 +0100 +++ vfs-2.6/Documentation/filesystems/proc.txt 2008-03-26 21:43:05.000000000 +0100 @@ -43,6 +43,7 @@ Table of Contents 2.13 /proc//oom_score - Display current oom-killer score 2.14 /proc//io - Display the IO accounting fields 2.15 /proc//coredump_filter - Core dump filtering settings + 2.16 /proc//mountinfo - Information about mounts ------------------------------------------------------------------------------ Preface @@ -2348,4 +2349,36 @@ For example: $ echo 0x7 > /proc/self/coredump_filter $ ./some_program +2.16 /proc//mountinfo - Information about mounts +-------------------------------------------------------- + +This file contains lines of the form: + +36 35 98:0 /mnt1 /mnt2 rw,noatime rw master:1 - ext3 /dev/root,errors=continue +(1)(2)(3) (4) (5) (6) (7) (8) (9) (10) (11) (12) + +(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) super options: filesystem type independent, per super block options +(8) optional fields: zero or more fields of the form "tag[:value]" +(9) separator: marks the end of the optional fields +(10) filesystem type: name of filesystem of the form "type[.subtype]" +(11) mount source: filesystem specific information or "none" +(12) filesystem options: filesystem type dependent 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 + ------------------------------------------------------------------------------ Index: vfs-2.6/fs/namespace.c =================================================================== --- vfs-2.6.orig/fs/namespace.c 2008-03-26 21:43:03.000000000 +0100 +++ vfs-2.6/fs/namespace.c 2008-03-26 21:43:05.000000000 +0100 @@ -753,20 +753,30 @@ static void m_stop(struct seq_file *m, v up_read(&namespace_sem); } -static int show_vfsmnt(struct seq_file *m, void *v) +struct proc_fs_info { + int flag; + const char *str; +}; + +static void show_sb_opts(struct seq_file *m, struct super_block *sb) { - struct vfsmount *mnt = list_entry(v, struct vfsmount, mnt_list); - int err = 0; - static struct proc_fs_info { - int flag; - char *str; - } fs_info[] = { + 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" }, @@ -775,27 +785,37 @@ static int show_vfsmnt(struct seq_file * { 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"); @@ -809,6 +829,61 @@ 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; + size_t count_save = m->count; + 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, rewind seq_file. Ugly, + * but necessary for race-free detection of unreachable + * mountpoints. + */ + m->count = count_save; + return 0; + } + seq_puts(m, mnt->mnt_flags & MNT_READONLY ? " ro" : " rw"); + show_mnt_opts(m, mnt); + seq_puts(m, sb->s_flags & MS_RDONLY ? " ro" : " rw"); + show_sb_opts(m, sb); + + /* 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"); + 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); @@ -829,7 +904,7 @@ static int show_vfsstat(struct seq_file /* 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) { Index: vfs-2.6/fs/proc/base.c =================================================================== --- vfs-2.6.orig/fs/proc/base.c 2008-03-26 21:43:03.000000000 +0100 +++ vfs-2.6/fs/proc/base.c 2008-03-26 21:43:05.000000000 +0100 @@ -604,6 +604,19 @@ static const struct file_operations proc .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); @@ -2285,6 +2298,7 @@ static const struct pid_entry tgid_base_ 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), @@ -2616,6 +2630,7 @@ static const struct pid_entry tid_base_s 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), Index: vfs-2.6/include/linux/mnt_namespace.h =================================================================== --- vfs-2.6.orig/include/linux/mnt_namespace.h 2008-03-26 21:43:03.000000000 +0100 +++ vfs-2.6/include/linux/mnt_namespace.h 2008-03-26 21:43:05.000000000 +0100 @@ -46,6 +46,7 @@ static inline void get_mnt_ns(struct mnt } extern const struct seq_operations mounts_op; +extern const struct seq_operations mountinfo_op; extern const struct seq_operations mountstats_op; #endif -- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/