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authorAl Viro <viro@zeniv.linux.org.uk>2018-03-06 03:15:50 +0300
committerAl Viro <viro@zeniv.linux.org.uk>2018-03-29 22:07:46 +0300
commit7a5cf791a747640adb2a1b5e3838321b26953a23 (patch)
tree9f0ccb7e00c71d575102c457cf695a6975e7c58a /fs/dcache.c
parent43986d63b60fd0152d9038ee3f0f9294efa8c983 (diff)
downloadlinux-7a5cf791a747640adb2a1b5e3838321b26953a23.tar.xz
split d_path() and friends into a separate file
Those parts of fs/dcache.c are pretty much self-contained. Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'fs/dcache.c')
-rw-r--r--fs/dcache.c467
1 files changed, 1 insertions, 466 deletions
diff --git a/fs/dcache.c b/fs/dcache.c
index 91626643fc86..c870343f904f 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -14,7 +14,7 @@
* the dcache entry is deleted or garbage collected.
*/
-#include <linux/syscalls.h>
+#include <linux/ratelimit.h>
#include <linux/string.h>
#include <linux/mm.h>
#include <linux/fs.h>
@@ -24,15 +24,11 @@
#include <linux/hash.h>
#include <linux/cache.h>
#include <linux/export.h>
-#include <linux/mount.h>
-#include <linux/uaccess.h>
#include <linux/security.h>
#include <linux/seqlock.h>
#include <linux/bootmem.h>
-#include <linux/fs_struct.h>
#include <linux/bit_spinlock.h>
#include <linux/rculist_bl.h>
-#include <linux/prefetch.h>
#include <linux/list_lru.h>
#include "internal.h"
#include "mount.h"
@@ -3072,467 +3068,6 @@ out:
}
EXPORT_SYMBOL(d_splice_alias);
-static int prepend(char **buffer, int *buflen, const char *str, int namelen)
-{
- *buflen -= namelen;
- if (*buflen < 0)
- return -ENAMETOOLONG;
- *buffer -= namelen;
- memcpy(*buffer, str, namelen);
- return 0;
-}
-
-/**
- * prepend_name - prepend a pathname in front of current buffer pointer
- * @buffer: buffer pointer
- * @buflen: allocated length of the buffer
- * @name: name string and length qstr structure
- *
- * With RCU path tracing, it may race with d_move(). Use READ_ONCE() to
- * make sure that either the old or the new name pointer and length are
- * fetched. However, there may be mismatch between length and pointer.
- * The length cannot be trusted, we need to copy it byte-by-byte until
- * the length is reached or a null byte is found. It also prepends "/" at
- * the beginning of the name. The sequence number check at the caller will
- * retry it again when a d_move() does happen. So any garbage in the buffer
- * due to mismatched pointer and length will be discarded.
- *
- * Load acquire is needed to make sure that we see that terminating NUL.
- */
-static int prepend_name(char **buffer, int *buflen, const struct qstr *name)
-{
- const char *dname = smp_load_acquire(&name->name); /* ^^^ */
- u32 dlen = READ_ONCE(name->len);
- char *p;
-
- *buflen -= dlen + 1;
- if (*buflen < 0)
- return -ENAMETOOLONG;
- p = *buffer -= dlen + 1;
- *p++ = '/';
- while (dlen--) {
- char c = *dname++;
- if (!c)
- break;
- *p++ = c;
- }
- return 0;
-}
-
-/**
- * prepend_path - Prepend path string to a buffer
- * @path: the dentry/vfsmount to report
- * @root: root vfsmnt/dentry
- * @buffer: pointer to the end of the buffer
- * @buflen: pointer to buffer length
- *
- * The function will first try to write out the pathname without taking any
- * lock other than the RCU read lock to make sure that dentries won't go away.
- * It only checks the sequence number of the global rename_lock as any change
- * in the dentry's d_seq will be preceded by changes in the rename_lock
- * sequence number. If the sequence number had been changed, it will restart
- * the whole pathname back-tracing sequence again by taking the rename_lock.
- * In this case, there is no need to take the RCU read lock as the recursive
- * parent pointer references will keep the dentry chain alive as long as no
- * rename operation is performed.
- */
-static int prepend_path(const struct path *path,
- const struct path *root,
- char **buffer, int *buflen)
-{
- struct dentry *dentry;
- struct vfsmount *vfsmnt;
- struct mount *mnt;
- int error = 0;
- unsigned seq, m_seq = 0;
- char *bptr;
- int blen;
-
- rcu_read_lock();
-restart_mnt:
- read_seqbegin_or_lock(&mount_lock, &m_seq);
- seq = 0;
- rcu_read_lock();
-restart:
- bptr = *buffer;
- blen = *buflen;
- error = 0;
- dentry = path->dentry;
- vfsmnt = path->mnt;
- mnt = real_mount(vfsmnt);
- read_seqbegin_or_lock(&rename_lock, &seq);
- while (dentry != root->dentry || vfsmnt != root->mnt) {
- struct dentry * parent;
-
- if (dentry == vfsmnt->mnt_root || IS_ROOT(dentry)) {
- struct mount *parent = READ_ONCE(mnt->mnt_parent);
- /* Escaped? */
- if (dentry != vfsmnt->mnt_root) {
- bptr = *buffer;
- blen = *buflen;
- error = 3;
- break;
- }
- /* Global root? */
- if (mnt != parent) {
- dentry = READ_ONCE(mnt->mnt_mountpoint);
- mnt = parent;
- vfsmnt = &mnt->mnt;
- continue;
- }
- if (!error)
- error = is_mounted(vfsmnt) ? 1 : 2;
- break;
- }
- parent = dentry->d_parent;
- prefetch(parent);
- error = prepend_name(&bptr, &blen, &dentry->d_name);
- if (error)
- break;
-
- dentry = parent;
- }
- if (!(seq & 1))
- rcu_read_unlock();
- if (need_seqretry(&rename_lock, seq)) {
- seq = 1;
- goto restart;
- }
- done_seqretry(&rename_lock, seq);
-
- if (!(m_seq & 1))
- rcu_read_unlock();
- if (need_seqretry(&mount_lock, m_seq)) {
- m_seq = 1;
- goto restart_mnt;
- }
- done_seqretry(&mount_lock, m_seq);
-
- if (error >= 0 && bptr == *buffer) {
- if (--blen < 0)
- error = -ENAMETOOLONG;
- else
- *--bptr = '/';
- }
- *buffer = bptr;
- *buflen = blen;
- return error;
-}
-
-/**
- * __d_path - return the path of a dentry
- * @path: the dentry/vfsmount to report
- * @root: root vfsmnt/dentry
- * @buf: buffer to return value in
- * @buflen: buffer length
- *
- * Convert a dentry into an ASCII path name.
- *
- * Returns a pointer into the buffer or an error code if the
- * path was too long.
- *
- * "buflen" should be positive.
- *
- * If the path is not reachable from the supplied root, return %NULL.
- */
-char *__d_path(const struct path *path,
- const struct path *root,
- char *buf, int buflen)
-{
- char *res = buf + buflen;
- int error;
-
- prepend(&res, &buflen, "\0", 1);
- error = prepend_path(path, root, &res, &buflen);
-
- if (error < 0)
- return ERR_PTR(error);
- if (error > 0)
- return NULL;
- return res;
-}
-
-char *d_absolute_path(const struct path *path,
- char *buf, int buflen)
-{
- struct path root = {};
- char *res = buf + buflen;
- int error;
-
- prepend(&res, &buflen, "\0", 1);
- error = prepend_path(path, &root, &res, &buflen);
-
- if (error > 1)
- error = -EINVAL;
- if (error < 0)
- return ERR_PTR(error);
- return res;
-}
-
-/*
- * same as __d_path but appends "(deleted)" for unlinked files.
- */
-static int path_with_deleted(const struct path *path,
- const struct path *root,
- char **buf, int *buflen)
-{
- prepend(buf, buflen, "\0", 1);
- if (d_unlinked(path->dentry)) {
- int error = prepend(buf, buflen, " (deleted)", 10);
- if (error)
- return error;
- }
-
- return prepend_path(path, root, buf, buflen);
-}
-
-static int prepend_unreachable(char **buffer, int *buflen)
-{
- return prepend(buffer, buflen, "(unreachable)", 13);
-}
-
-static void get_fs_root_rcu(struct fs_struct *fs, struct path *root)
-{
- unsigned seq;
-
- do {
- seq = read_seqcount_begin(&fs->seq);
- *root = fs->root;
- } while (read_seqcount_retry(&fs->seq, seq));
-}
-
-/**
- * d_path - return the path of a dentry
- * @path: path to report
- * @buf: buffer to return value in
- * @buflen: buffer length
- *
- * Convert a dentry into an ASCII path name. If the entry has been deleted
- * the string " (deleted)" is appended. Note that this is ambiguous.
- *
- * Returns a pointer into the buffer or an error code if the path was
- * too long. Note: Callers should use the returned pointer, not the passed
- * in buffer, to use the name! The implementation often starts at an offset
- * into the buffer, and may leave 0 bytes at the start.
- *
- * "buflen" should be positive.
- */
-char *d_path(const struct path *path, char *buf, int buflen)
-{
- char *res = buf + buflen;
- struct path root;
- int error;
-
- /*
- * We have various synthetic filesystems that never get mounted. On
- * these filesystems dentries are never used for lookup purposes, and
- * thus don't need to be hashed. They also don't need a name until a
- * user wants to identify the object in /proc/pid/fd/. The little hack
- * below allows us to generate a name for these objects on demand:
- *
- * Some pseudo inodes are mountable. When they are mounted
- * path->dentry == path->mnt->mnt_root. In that case don't call d_dname
- * and instead have d_path return the mounted path.
- */
- if (path->dentry->d_op && path->dentry->d_op->d_dname &&
- (!IS_ROOT(path->dentry) || path->dentry != path->mnt->mnt_root))
- return path->dentry->d_op->d_dname(path->dentry, buf, buflen);
-
- rcu_read_lock();
- get_fs_root_rcu(current->fs, &root);
- error = path_with_deleted(path, &root, &res, &buflen);
- rcu_read_unlock();
-
- if (error < 0)
- res = ERR_PTR(error);
- return res;
-}
-EXPORT_SYMBOL(d_path);
-
-/*
- * Helper function for dentry_operations.d_dname() members
- */
-char *dynamic_dname(struct dentry *dentry, char *buffer, int buflen,
- const char *fmt, ...)
-{
- va_list args;
- char temp[64];
- int sz;
-
- va_start(args, fmt);
- sz = vsnprintf(temp, sizeof(temp), fmt, args) + 1;
- va_end(args);
-
- if (sz > sizeof(temp) || sz > buflen)
- return ERR_PTR(-ENAMETOOLONG);
-
- buffer += buflen - sz;
- return memcpy(buffer, temp, sz);
-}
-
-char *simple_dname(struct dentry *dentry, char *buffer, int buflen)
-{
- char *end = buffer + buflen;
- /* these dentries are never renamed, so d_lock is not needed */
- if (prepend(&end, &buflen, " (deleted)", 11) ||
- prepend(&end, &buflen, dentry->d_name.name, dentry->d_name.len) ||
- prepend(&end, &buflen, "/", 1))
- end = ERR_PTR(-ENAMETOOLONG);
- return end;
-}
-EXPORT_SYMBOL(simple_dname);
-
-/*
- * Write full pathname from the root of the filesystem into the buffer.
- */
-static char *__dentry_path(struct dentry *d, char *buf, int buflen)
-{
- struct dentry *dentry;
- char *end, *retval;
- int len, seq = 0;
- int error = 0;
-
- if (buflen < 2)
- goto Elong;
-
- rcu_read_lock();
-restart:
- dentry = d;
- end = buf + buflen;
- len = buflen;
- prepend(&end, &len, "\0", 1);
- /* Get '/' right */
- retval = end-1;
- *retval = '/';
- read_seqbegin_or_lock(&rename_lock, &seq);
- while (!IS_ROOT(dentry)) {
- struct dentry *parent = dentry->d_parent;
-
- prefetch(parent);
- error = prepend_name(&end, &len, &dentry->d_name);
- if (error)
- break;
-
- retval = end;
- dentry = parent;
- }
- if (!(seq & 1))
- rcu_read_unlock();
- if (need_seqretry(&rename_lock, seq)) {
- seq = 1;
- goto restart;
- }
- done_seqretry(&rename_lock, seq);
- if (error)
- goto Elong;
- return retval;
-Elong:
- return ERR_PTR(-ENAMETOOLONG);
-}
-
-char *dentry_path_raw(struct dentry *dentry, char *buf, int buflen)
-{
- return __dentry_path(dentry, buf, buflen);
-}
-EXPORT_SYMBOL(dentry_path_raw);
-
-char *dentry_path(struct dentry *dentry, char *buf, int buflen)
-{
- char *p = NULL;
- char *retval;
-
- if (d_unlinked(dentry)) {
- p = buf + buflen;
- if (prepend(&p, &buflen, "//deleted", 10) != 0)
- goto Elong;
- buflen++;
- }
- retval = __dentry_path(dentry, buf, buflen);
- if (!IS_ERR(retval) && p)
- *p = '/'; /* restore '/' overriden with '\0' */
- return retval;
-Elong:
- return ERR_PTR(-ENAMETOOLONG);
-}
-
-static void get_fs_root_and_pwd_rcu(struct fs_struct *fs, struct path *root,
- struct path *pwd)
-{
- unsigned seq;
-
- do {
- seq = read_seqcount_begin(&fs->seq);
- *root = fs->root;
- *pwd = fs->pwd;
- } while (read_seqcount_retry(&fs->seq, seq));
-}
-
-/*
- * NOTE! The user-level library version returns a
- * character pointer. The kernel system call just
- * returns the length of the buffer filled (which
- * includes the ending '\0' character), or a negative
- * error value. So libc would do something like
- *
- * char *getcwd(char * buf, size_t size)
- * {
- * int retval;
- *
- * retval = sys_getcwd(buf, size);
- * if (retval >= 0)
- * return buf;
- * errno = -retval;
- * return NULL;
- * }
- */
-SYSCALL_DEFINE2(getcwd, char __user *, buf, unsigned long, size)
-{
- int error;
- struct path pwd, root;
- char *page = __getname();
-
- if (!page)
- return -ENOMEM;
-
- rcu_read_lock();
- get_fs_root_and_pwd_rcu(current->fs, &root, &pwd);
-
- error = -ENOENT;
- if (!d_unlinked(pwd.dentry)) {
- unsigned long len;
- char *cwd = page + PATH_MAX;
- int buflen = PATH_MAX;
-
- prepend(&cwd, &buflen, "\0", 1);
- error = prepend_path(&pwd, &root, &cwd, &buflen);
- rcu_read_unlock();
-
- if (error < 0)
- goto out;
-
- /* Unreachable from current root */
- if (error > 0) {
- error = prepend_unreachable(&cwd, &buflen);
- if (error)
- goto out;
- }
-
- error = -ERANGE;
- len = PATH_MAX + page - cwd;
- if (len <= size) {
- error = len;
- if (copy_to_user(buf, cwd, len))
- error = -EFAULT;
- }
- } else {
- rcu_read_unlock();
- }
-
-out:
- __putname(page);
- return error;
-}
-
/*
* Test whether new_dentry is a subdirectory of old_dentry.
*