forked from Minki/linux
VFS: replace {, total_}link_count in task_struct with pointer to nameidata
task_struct currently contains two ad-hoc members for use by the VFS: link_count and total_link_count. These are only interesting to fs/namei.c, so exposing them explicitly is poor layering. Incidentally, link_count isn't used anymore, so it can just die. This patches replaces those with a single pointer to 'struct nameidata'. This structure represents the current filename lookup of which there can only be one per process, and is a natural place to store total_link_count. This will allow the current "nameidata" argument to all follow_link operations to be removed as current->nameidata can be used instead in the _very_ few instances that care about it at all. As there are occasional circumstances where pathname lookup can recurse, such as through kern_path_locked, we always save and old current->nameidata (if there is one) when setting a new value, and make sure any active link_counts are preserved. follow_mount and follow_automount now get a 'struct nameidata *' rather than 'int flags' so that they can directly access total_link_count, rather than going through 'current'. Suggested-by: Al Viro <viro@ZenIV.linux.org.uk> Signed-off-by: NeilBrown <neilb@suse.de> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
NeilBrown
Al Viro
parent
44163f3005
commit
756daf263e
70
fs/namei.c
70
fs/namei.c
@ -505,6 +505,7 @@ struct nameidata {
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unsigned seq, m_seq;
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int last_type;
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unsigned depth;
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int total_link_count;
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struct file *base;
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struct saved {
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struct path link;
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@ -513,16 +514,25 @@ struct nameidata {
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} *stack, internal[EMBEDDED_LEVELS];
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};
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static void set_nameidata(struct nameidata *nd)
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static struct nameidata *set_nameidata(struct nameidata *p)
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{
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nd->stack = nd->internal;
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struct nameidata *old = current->nameidata;
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p->stack = p->internal;
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p->total_link_count = old ? old->total_link_count : 0;
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current->nameidata = p;
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return old;
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}
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static void restore_nameidata(struct nameidata *nd)
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static void restore_nameidata(struct nameidata *old)
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{
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if (nd->stack != nd->internal) {
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kfree(nd->stack);
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nd->stack = nd->internal;
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struct nameidata *now = current->nameidata;
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current->nameidata = old;
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if (old)
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old->total_link_count = now->total_link_count;
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if (now->stack != now->internal) {
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kfree(now->stack);
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now->stack = now->internal;
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}
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}
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@ -970,7 +980,7 @@ EXPORT_SYMBOL(follow_up);
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* - return -EISDIR to tell follow_managed() to stop and return the path we
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* were called with.
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*/
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static int follow_automount(struct path *path, unsigned flags,
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static int follow_automount(struct path *path, struct nameidata *nd,
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bool *need_mntput)
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{
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struct vfsmount *mnt;
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@ -990,13 +1000,13 @@ static int follow_automount(struct path *path, unsigned flags,
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* as being automount points. These will need the attentions
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* of the daemon to instantiate them before they can be used.
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*/
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if (!(flags & (LOOKUP_PARENT | LOOKUP_DIRECTORY |
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LOOKUP_OPEN | LOOKUP_CREATE | LOOKUP_AUTOMOUNT)) &&
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if (!(nd->flags & (LOOKUP_PARENT | LOOKUP_DIRECTORY |
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LOOKUP_OPEN | LOOKUP_CREATE | LOOKUP_AUTOMOUNT)) &&
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path->dentry->d_inode)
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return -EISDIR;
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current->total_link_count++;
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if (current->total_link_count >= 40)
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nd->total_link_count++;
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if (nd->total_link_count >= 40)
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return -ELOOP;
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mnt = path->dentry->d_op->d_automount(path);
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@ -1010,7 +1020,7 @@ static int follow_automount(struct path *path, unsigned flags,
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* the path being looked up; if it wasn't then the remainder of
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* the path is inaccessible and we should say so.
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*/
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if (PTR_ERR(mnt) == -EISDIR && (flags & LOOKUP_PARENT))
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if (PTR_ERR(mnt) == -EISDIR && (nd->flags & LOOKUP_PARENT))
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return -EREMOTE;
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return PTR_ERR(mnt);
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}
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@ -1050,7 +1060,7 @@ static int follow_automount(struct path *path, unsigned flags,
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*
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* Serialization is taken care of in namespace.c
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*/
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static int follow_managed(struct path *path, unsigned flags)
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static int follow_managed(struct path *path, struct nameidata *nd)
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{
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struct vfsmount *mnt = path->mnt; /* held by caller, must be left alone */
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unsigned managed;
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@ -1094,7 +1104,7 @@ static int follow_managed(struct path *path, unsigned flags)
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/* Handle an automount point */
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if (managed & DCACHE_NEED_AUTOMOUNT) {
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ret = follow_automount(path, flags, &need_mntput);
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ret = follow_automount(path, nd, &need_mntput);
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if (ret < 0)
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break;
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continue;
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@ -1483,7 +1493,7 @@ unlazy:
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}
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path->mnt = mnt;
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path->dentry = dentry;
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err = follow_managed(path, nd->flags);
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err = follow_managed(path, nd);
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if (unlikely(err < 0)) {
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path_put_conditional(path, nd);
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return err;
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@ -1513,7 +1523,7 @@ static int lookup_slow(struct nameidata *nd, struct path *path)
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return PTR_ERR(dentry);
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path->mnt = nd->path.mnt;
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path->dentry = dentry;
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err = follow_managed(path, nd->flags);
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err = follow_managed(path, nd);
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if (unlikely(err < 0)) {
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path_put_conditional(path, nd);
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return err;
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@ -1563,7 +1573,7 @@ static void terminate_walk(struct nameidata *nd)
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static int pick_link(struct nameidata *nd, struct path *link)
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{
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int error;
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if (unlikely(current->total_link_count++ >= MAXSYMLINKS)) {
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if (unlikely(nd->total_link_count++ >= MAXSYMLINKS)) {
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path_to_nameidata(link, nd);
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return -ELOOP;
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}
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@ -1981,7 +1991,7 @@ static int path_init(int dfd, const struct filename *name, unsigned int flags,
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rcu_read_unlock();
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return -ECHILD;
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done:
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current->total_link_count = 0;
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nd->total_link_count = 0;
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return link_path_walk(s, nd);
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}
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@ -2087,10 +2097,9 @@ static int filename_lookup(int dfd, struct filename *name,
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unsigned int flags, struct nameidata *nd)
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{
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int retval;
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struct nameidata *saved_nd = set_nameidata(nd);
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set_nameidata(nd);
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retval = path_lookupat(dfd, name, flags | LOOKUP_RCU, nd);
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if (unlikely(retval == -ECHILD))
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retval = path_lookupat(dfd, name, flags, nd);
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if (unlikely(retval == -ESTALE))
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@ -2098,7 +2107,7 @@ static int filename_lookup(int dfd, struct filename *name,
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if (likely(!retval))
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audit_inode(name, nd->path.dentry, flags & LOOKUP_PARENT);
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restore_nameidata(nd);
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restore_nameidata(saved_nd);
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return retval;
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}
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@ -2426,11 +2435,11 @@ static int
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filename_mountpoint(int dfd, struct filename *name, struct path *path,
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unsigned int flags)
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{
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struct nameidata nd;
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struct nameidata nd, *saved;
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int error;
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if (IS_ERR(name))
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return PTR_ERR(name);
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set_nameidata(&nd);
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saved = set_nameidata(&nd);
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error = path_mountpoint(dfd, name, path, &nd, flags | LOOKUP_RCU);
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if (unlikely(error == -ECHILD))
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error = path_mountpoint(dfd, name, path, &nd, flags);
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@ -2438,7 +2447,7 @@ filename_mountpoint(int dfd, struct filename *name, struct path *path,
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error = path_mountpoint(dfd, name, path, &nd, flags | LOOKUP_REVAL);
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if (likely(!error))
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audit_inode(name, path->dentry, 0);
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restore_nameidata(&nd);
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restore_nameidata(saved);
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putname(name);
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return error;
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}
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@ -3087,7 +3096,7 @@ retry_lookup:
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if ((open_flag & (O_EXCL | O_CREAT)) == (O_EXCL | O_CREAT))
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goto exit_dput;
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error = follow_managed(&path, nd->flags);
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error = follow_managed(&path, nd);
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if (error < 0)
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goto exit_dput;
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@ -3323,31 +3332,29 @@ out2:
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struct file *do_filp_open(int dfd, struct filename *pathname,
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const struct open_flags *op)
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{
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struct nameidata nd;
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struct nameidata nd, *saved_nd = set_nameidata(&nd);
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int flags = op->lookup_flags;
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struct file *filp;
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set_nameidata(&nd);
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filp = path_openat(dfd, pathname, &nd, op, flags | LOOKUP_RCU);
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if (unlikely(filp == ERR_PTR(-ECHILD)))
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filp = path_openat(dfd, pathname, &nd, op, flags);
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if (unlikely(filp == ERR_PTR(-ESTALE)))
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filp = path_openat(dfd, pathname, &nd, op, flags | LOOKUP_REVAL);
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restore_nameidata(&nd);
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restore_nameidata(saved_nd);
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return filp;
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}
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struct file *do_file_open_root(struct dentry *dentry, struct vfsmount *mnt,
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const char *name, const struct open_flags *op)
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{
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struct nameidata nd;
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struct nameidata nd, *saved_nd;
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struct file *file;
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struct filename *filename;
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int flags = op->lookup_flags | LOOKUP_ROOT;
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nd.root.mnt = mnt;
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nd.root.dentry = dentry;
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set_nameidata(&nd);
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if (d_is_symlink(dentry) && op->intent & LOOKUP_OPEN)
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return ERR_PTR(-ELOOP);
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@ -3356,12 +3363,13 @@ struct file *do_file_open_root(struct dentry *dentry, struct vfsmount *mnt,
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if (unlikely(IS_ERR(filename)))
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return ERR_CAST(filename);
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saved_nd = set_nameidata(&nd);
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file = path_openat(-1, filename, &nd, op, flags | LOOKUP_RCU);
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if (unlikely(file == ERR_PTR(-ECHILD)))
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file = path_openat(-1, filename, &nd, op, flags);
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if (unlikely(file == ERR_PTR(-ESTALE)))
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file = path_openat(-1, filename, &nd, op, flags | LOOKUP_REVAL);
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restore_nameidata(&nd);
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restore_nameidata(saved_nd);
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putname(filename);
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return file;
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}
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@ -1461,7 +1461,7 @@ struct task_struct {
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it with task_lock())
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- initialized normally by setup_new_exec */
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/* file system info */
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int link_count, total_link_count;
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struct nameidata *nameidata;
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#ifdef CONFIG_SYSVIPC
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/* ipc stuff */
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struct sysv_sem sysvsem;
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