This patch disambiguates multiple mount-instances of the same filesystem (or part of the same filesystem), by introducing a new interface /proc/mounts_new. The interface has the following format. ------------------------------------------------------------ FSID mntpt root-dentry fstype fs-options ------------------------------------------------------------ NOTE: root-dentry is the path to the dentry w.r.t to the root dentry of the same filesystem. for example: lets say we attempt the following commands mount --bind /var /mnt mount --bind /mnt/tmp /tmp1 'cat /proc/mounts' shows the following: /dev/root /mnt ext2 rw 0 0 /dev/root /tmp1 ext2 rw 0 0 NOTE: The above mount entries, do not indicate that /tmp1 contains the same directory tree as /var/tmp. But 'cat /proc/mounts_new' shows us the following: 0x6200 /mnt /var ext2 rw 0 0 0x6200 /tmp1 /var/tmp ext2 rw 0 0 The above entries clearly indicates that /var/tmp directory of the ext2 filesystem with fsid=0x6200 is the directory tree that resides under /tmp1 Signed-off-by: Ram Pai --- fs/dcache.c | 53 ++++++++++++++++++++++++++++++++ fs/namespace.c | 35 ++++++++++++++++++--- fs/proc/base.c | 32 +++++++++++++++++-- fs/proc/proc_misc.c | 1 fs/seq_file.c | 77 ++++++++++++++++++++++++++++++++++------------- include/linux/dcache.h | 1 include/linux/seq_file.h | 1 7 files changed, 172 insertions(+), 28 deletions(-) Index: linux-2.6.17.10/fs/proc/base.c =================================================================== --- linux-2.6.17.10.orig/fs/proc/base.c +++ linux-2.6.17.10/fs/proc/base.c @@ -104,6 +104,7 @@ enum pid_directory_inos { PROC_TGID_MAPS, PROC_TGID_NUMA_MAPS, PROC_TGID_MOUNTS, + PROC_TGID_MOUNTS_NEW, PROC_TGID_MOUNTSTATS, PROC_TGID_WCHAN, #ifdef CONFIG_MMU @@ -145,6 +146,7 @@ enum pid_directory_inos { PROC_TID_MAPS, PROC_TID_NUMA_MAPS, PROC_TID_MOUNTS, + PROC_TID_MOUNTS_NEW, PROC_TID_MOUNTSTATS, PROC_TID_WCHAN, #ifdef CONFIG_MMU @@ -203,6 +205,7 @@ static struct pid_entry tgid_base_stuff[ E(PROC_TGID_ROOT, "root", S_IFLNK|S_IRWXUGO), E(PROC_TGID_EXE, "exe", S_IFLNK|S_IRWXUGO), E(PROC_TGID_MOUNTS, "mounts", S_IFREG|S_IRUGO), + E(PROC_TGID_MOUNTS_NEW,"mounts_new", S_IFREG|S_IRUGO), E(PROC_TGID_MOUNTSTATS, "mountstats", S_IFREG|S_IRUSR), #ifdef CONFIG_MMU E(PROC_TGID_SMAPS, "smaps", S_IFREG|S_IRUGO), @@ -246,6 +249,7 @@ static struct pid_entry tid_base_stuff[] E(PROC_TID_ROOT, "root", S_IFLNK|S_IRWXUGO), E(PROC_TID_EXE, "exe", S_IFLNK|S_IRWXUGO), E(PROC_TID_MOUNTS, "mounts", S_IFREG|S_IRUGO), + E(PROC_TID_MOUNTS_NEW, "mounts_new", S_IFREG|S_IRUGO), #ifdef CONFIG_MMU E(PROC_TID_SMAPS, "smaps", S_IFREG|S_IRUGO), #endif @@ -692,13 +696,13 @@ static struct file_operations proc_smaps }; #endif -extern struct seq_operations mounts_op; struct proc_mounts { struct seq_file m; int event; }; -static int mounts_open(struct inode *inode, struct file *file) +static int __mounts_open(struct inode *inode, struct file *file, + struct seq_operations *mounts_op) { struct task_struct *task = proc_task(inode); struct namespace *namespace; @@ -716,7 +720,7 @@ static int mounts_open(struct inode *ino p = kmalloc(sizeof(struct proc_mounts), GFP_KERNEL); if (p) { file->private_data = &p->m; - ret = seq_open(file, &mounts_op); + ret = seq_open(file, mounts_op); if (!ret) { p->m.private = namespace; p->event = namespace->event; @@ -729,6 +733,16 @@ static int mounts_open(struct inode *ino return ret; } +extern struct seq_operations mounts_op, mounts_new_op; +static int mounts_open(struct inode *inode, struct file *file) +{ + return (__mounts_open(inode, file, &mounts_op)); +} +static int mounts_new_open(struct inode *inode, struct file *file) +{ + return __mounts_open(inode, file, &mounts_new_op); +} + static int mounts_release(struct inode *inode, struct file *file) { struct seq_file *m = file->private_data; @@ -763,6 +777,14 @@ static struct file_operations proc_mount .poll = mounts_poll, }; +static struct file_operations proc_mounts_new_operations = { + .open = mounts_new_open, + .read = seq_read, + .llseek = seq_lseek, + .release = mounts_release, + .poll = mounts_poll, +}; + extern struct seq_operations mountstats_op; static int mountstats_open(struct inode *inode, struct file *file) { @@ -1799,6 +1821,10 @@ static struct dentry *proc_pident_lookup case PROC_TGID_MOUNTS: inode->i_fop = &proc_mounts_operations; break; + case PROC_TID_MOUNTS_NEW: + case PROC_TGID_MOUNTS_NEW: + inode->i_fop = &proc_mounts_new_operations; + break; #ifdef CONFIG_MMU case PROC_TID_SMAPS: case PROC_TGID_SMAPS: Index: linux-2.6.17.10/fs/dcache.c =================================================================== --- linux-2.6.17.10.orig/fs/dcache.c +++ linux-2.6.17.10/fs/dcache.c @@ -1477,6 +1477,59 @@ char * d_path(struct dentry *dentry, str return res; } +static inline int prepend(char **buffer, int *buflen, const char *str, + int namelen) +{ + if ((*buflen -= namelen) < 0) + return 1; + *buffer -= namelen; + memcpy(*buffer, str, namelen); + return 0; +} + +/* + * write full pathname into buffer and return start of pathname. + * If @vfsmnt is not specified return the path relative to the + * its filesystem's root. + */ +char * dentry_path(struct dentry *dentry, char *buf, int buflen) +{ + char * end = buf+buflen; + char * retval; + + spin_lock(&dcache_lock); + prepend(&end, &buflen, "\0", 1); + if (!IS_ROOT(dentry) && d_unhashed(dentry)) { + if (prepend(&end, &buflen, "//deleted", 10)) + goto Elong; + } + /* Get '/' right */ + retval = end-1; + *retval = '/'; + + for (;;) { + struct dentry * parent; + if (IS_ROOT(dentry)) + break; + + parent = dentry->d_parent; + prefetch(parent); + + if (prepend(&end, &buflen, dentry->d_name.name, + dentry->d_name.len) || + prepend(&end, &buflen, "/", 1)) + goto Elong; + + retval = end; + dentry = parent; + } + spin_unlock(&dcache_lock); + return retval; +Elong: + spin_unlock(&dcache_lock); + return ERR_PTR(-ENAMETOOLONG); +} + /* * NOTE! The user-level library version returns a * character pointer. The kernel system call just Index: linux-2.6.17.10/fs/seq_file.c =================================================================== --- linux-2.6.17.10.orig/fs/seq_file.c +++ linux-2.6.17.10/fs/seq_file.c @@ -338,38 +338,75 @@ int seq_printf(struct seq_file *m, const } EXPORT_SYMBOL(seq_printf); -int seq_path(struct seq_file *m, - struct vfsmount *mnt, struct dentry *dentry, +static inline char *mangle_path(char *s, char *p, char *esc) +{ + while (s <= p) { + char c = *p++; + if (!c) { + return s; + } else if (!strchr(esc, c)) { + *s++ = c; + } else if (s + 4 > p) { + break; + } else { + *s++ = '\\'; + *s++ = '0' + ((c & 0300) >> 6); + *s++ = '0' + ((c & 070) >> 3); + *s++ = '0' + (c & 07); + } + } + return NULL; +} + +/* + * return the absolute path of 'dentry' residing in mount 'mnt'. + */ +int seq_path(struct seq_file *m, struct vfsmount *mnt, struct dentry *dentry, char *esc) { + char *p = NULL; if (m->count < m->size) { char *s = m->buf + m->count; - char *p = d_path(dentry, mnt, s, m->size - m->count); + p = d_path(dentry, mnt, s, m->size - m->count); if (!IS_ERR(p)) { - while (s <= p) { - char c = *p++; - if (!c) { - p = m->buf + m->count; - m->count = s - m->buf; - return s - p; - } else if (!strchr(esc, c)) { - *s++ = c; - } else if (s + 4 > p) { - break; - } else { - *s++ = '\\'; - *s++ = '0' + ((c & 0300) >> 6); - *s++ = '0' + ((c & 070) >> 3); - *s++ = '0' + (c & 07); - } + s = mangle_path(s, p, esc); + if (s) { + p = m->buf + m->count; + m->count = s - m->buf; + return s - p; } } } m->count = m->size; - return -1; + return p == ERR_PTR(-ENAMETOOLONG) ? 0 : -1; } + EXPORT_SYMBOL(seq_path); +/* + * returns the path of the 'dentry' from the root of its filesystem. + */ +int seq_dentry(struct seq_file *m, struct dentry *dentry, char *esc) +{ + char *p = NULL; + if (m->count < m->size) { + char *s = m->buf + m->count; + p = dentry_path(dentry, s, m->size - m->count); + if (!IS_ERR(p)) { + s = mangle_path(s, p, esc); + if (s) { + p = m->buf + m->count; + m->count = s - m->buf; + return s - p; + } + } + } + m->count = m->size; + return p == ERR_PTR(-ENAMETOOLONG) ? 0 : -1; +} + +EXPORT_SYMBOL(seq_dentry); + static void *single_start(struct seq_file *p, loff_t *pos) { return NULL + (*pos == 0); Index: linux-2.6.17.10/fs/proc/proc_misc.c =================================================================== --- linux-2.6.17.10.orig/fs/proc/proc_misc.c +++ linux-2.6.17.10/fs/proc/proc_misc.c @@ -675,6 +675,7 @@ void __init proc_misc_init(void) create_proc_read_entry(p->name, 0, NULL, p->read_proc, NULL); proc_symlink("mounts", NULL, "self/mounts"); + proc_symlink("mounts_new", NULL, "self/mounts_new"); /* And now for trickier ones */ entry = create_proc_entry("kmsg", S_IRUSR, &proc_root); Index: linux-2.6.17.10/fs/namespace.c =================================================================== --- linux-2.6.17.10.orig/fs/namespace.c +++ linux-2.6.17.10/fs/namespace.c @@ -349,7 +349,7 @@ static inline void mangle(struct seq_fil seq_escape(m, s, " \t\n\\"); } -static int show_vfsmnt(struct seq_file *m, void *v) +static int show_options(struct seq_file *m, void *v) { struct vfsmount *mnt = v; int err = 0; @@ -372,10 +372,6 @@ static int show_vfsmnt(struct seq_file * }; struct proc_fs_info *fs_infop; - mangle(m, mnt->mnt_devname ? mnt->mnt_devname : "none"); - seq_putc(m, ' '); - seq_path(m, mnt, mnt->mnt_root, " \t\n\\"); - seq_putc(m, ' '); mangle(m, mnt->mnt_sb->s_type->name); seq_puts(m, mnt->mnt_sb->s_flags & MS_RDONLY ? " ro" : " rw"); for (fs_infop = fs_info; fs_infop->flag; fs_infop++) { @@ -392,6 +388,28 @@ static int show_vfsmnt(struct seq_file * return err; } +static int show_vfsmnt(struct seq_file *m, void *v) +{ + struct vfsmount *mnt = v; + mangle(m, mnt->mnt_devname ? mnt->mnt_devname : "none"); + seq_putc(m, ' '); + seq_path(m, mnt, mnt->mnt_root, " \t\n\\"); + seq_putc(m, ' '); + return show_options(m, v); +} + +static int show_vfsmnt_new(struct seq_file *m, void *v) +{ + struct vfsmount *mnt = v; + seq_printf(m, "0x%x", new_encode_dev(mnt->mnt_sb->s_dev)); + seq_putc(m, ' '); + seq_path(m, mnt, mnt->mnt_root, " \t\n\\"); + seq_putc(m, ' '); + seq_dentry(m, mnt->mnt_root, " \t\n\\"); + seq_putc(m, ' '); + return show_options(m, v); +} + struct seq_operations mounts_op = { .start = m_start, .next = m_next, @@ -399,6 +417,13 @@ struct seq_operations mounts_op = { .show = show_vfsmnt }; +struct seq_operations mounts_new_op = { + .start = m_start, + .next = m_next, + .stop = m_stop, + .show = show_vfsmnt_new +}; + static int show_vfsstat(struct seq_file *m, void *v) { struct vfsmount *mnt = v; Index: linux-2.6.17.10/include/linux/dcache.h =================================================================== --- linux-2.6.17.10.orig/include/linux/dcache.h +++ linux-2.6.17.10/include/linux/dcache.h @@ -281,6 +281,7 @@ extern struct dentry * d_hash_and_lookup extern int d_validate(struct dentry *, struct dentry *); extern char * d_path(struct dentry *, struct vfsmount *, char *, int); +extern char * dentry_path(struct dentry *, char *, int); /* Allocation counts.. */ Index: linux-2.6.17.10/include/linux/seq_file.h =================================================================== --- linux-2.6.17.10.orig/include/linux/seq_file.h +++ linux-2.6.17.10/include/linux/seq_file.h @@ -43,6 +43,7 @@ int seq_printf(struct seq_file *, const __attribute__ ((format (printf,2,3))); int seq_path(struct seq_file *, struct vfsmount *, struct dentry *, char *); +int seq_dentry(struct seq_file *, struct dentry *, char *); int single_open(struct file *, int (*)(struct seq_file *, void *), void *); int single_release(struct inode *, struct file *);