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follow_dotdot{,_rcu}(): lift switching nd->path to parent out of loop 

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2020-02-26 11:55:02 -05:00
parent a6a7eb7628
commit abc2c632e0
1 changed files with 12 additions and 8 deletions
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20
fs/namei.c
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@ -1365,7 +1365,9 @@ static inline int handle_mounts(struct nameidata *nd, struct dentry *dentry,
static int follow_dotdot_rcu(struct nameidata *nd) static int follow_dotdot_rcu(struct nameidata *nd)
{ {
struct dentry *parent = NULL;
struct inode *inode = nd->inode; struct inode *inode = nd->inode;
unsigned seq;
while (1) { while (1) {
if (path_equal(&nd->path, &nd->root)) { if (path_equal(&nd->path, &nd->root)) {
@ -1375,15 +1377,12 @@ static int follow_dotdot_rcu(struct nameidata *nd)
} }
if (nd->path.dentry != nd->path.mnt->mnt_root) { if (nd->path.dentry != nd->path.mnt->mnt_root) {
struct dentry *old = nd->path.dentry; struct dentry *old = nd->path.dentry;
struct dentry *parent = old->d_parent;
unsigned seq;
parent = old->d_parent;
inode = parent->d_inode; inode = parent->d_inode;
seq = read_seqcount_begin(&parent->d_seq); seq = read_seqcount_begin(&parent->d_seq);
if (unlikely(read_seqcount_retry(&old->d_seq, nd->seq))) if (unlikely(read_seqcount_retry(&old->d_seq, nd->seq)))
return -ECHILD; return -ECHILD;
nd->path.dentry = parent;
nd->seq = seq;
if (unlikely(!path_connected(nd->path.mnt, parent))) if (unlikely(!path_connected(nd->path.mnt, parent)))
return -ECHILD; return -ECHILD;
break; break;
@ -1406,6 +1405,10 @@ static int follow_dotdot_rcu(struct nameidata *nd)
nd->seq = seq; nd->seq = seq;
} }
} }
if (likely(parent)) {
nd->path.dentry = parent;
nd->seq = seq;
}
while (unlikely(d_mountpoint(nd->path.dentry))) { while (unlikely(d_mountpoint(nd->path.dentry))) {
struct mount *mounted; struct mount *mounted;
mounted = __lookup_mnt(nd->path.mnt, nd->path.dentry); mounted = __lookup_mnt(nd->path.mnt, nd->path.dentry);
@ -1442,7 +1445,7 @@ static void follow_mount(struct path *path)
static int follow_dotdot(struct nameidata *nd) static int follow_dotdot(struct nameidata *nd)
{ {
struct dentry *parent; struct dentry *parent = NULL;
while (1) { while (1) {
if (path_equal(&nd->path, &nd->root)) { if (path_equal(&nd->path, &nd->root)) {
if (unlikely(nd->flags & LOOKUP_BENEATH)) if (unlikely(nd->flags & LOOKUP_BENEATH))
@ -1452,13 +1455,10 @@ static int follow_dotdot(struct nameidata *nd)
if (nd->path.dentry != nd->path.mnt->mnt_root) { if (nd->path.dentry != nd->path.mnt->mnt_root) {
/* rare case of legitimate dget_parent()... */ /* rare case of legitimate dget_parent()... */
parent = dget_parent(nd->path.dentry); parent = dget_parent(nd->path.dentry);
if (unlikely(!path_connected(nd->path.mnt, parent))) { if (unlikely(!path_connected(nd->path.mnt, parent))) {
dput(parent); dput(parent);
return -ENOENT; return -ENOENT;
} }
dput(nd->path.dentry);
nd->path.dentry = parent;
break; break;
} }
if (!follow_up(&nd->path)) if (!follow_up(&nd->path))
@ -1466,6 +1466,10 @@ static int follow_dotdot(struct nameidata *nd)
if (unlikely(nd->flags & LOOKUP_NO_XDEV)) if (unlikely(nd->flags & LOOKUP_NO_XDEV))
return -EXDEV; return -EXDEV;
} }
if (likely(parent)) {
dput(nd->path.dentry);
nd->path.dentry = parent;
}
follow_mount(&nd->path); follow_mount(&nd->path);
nd->inode = nd->path.dentry->d_inode; nd->inode = nd->path.dentry->d_inode;
return 0; return 0;