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step_into(): move fetching ->d_inode past handle_mounts() 

... and lose messing with it in __follow_mount_rcu()

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2022-07-03 22:35:56 -04:00
parent 4cb6402480
commit 3bd8bc8971
1 changed files with 11 additions and 20 deletions
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31
fs/namei.c
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@ -1474,8 +1474,7 @@ EXPORT_SYMBOL(follow_down);
* Try to skip to top of mountpoint pile in rcuwalk mode. Fail if
* we meet a managed dentry that would need blocking.
*/
static bool __follow_mount_rcu(struct nameidata *nd, struct path *path,
struct inode **inode)
static bool __follow_mount_rcu(struct nameidata *nd, struct path *path)
{
struct dentry *dentry = path->dentry;
unsigned int flags = dentry->d_flags;
@ -1505,13 +1504,6 @@ static bool __follow_mount_rcu(struct nameidata *nd, struct path *path,
dentry = path->dentry = mounted->mnt.mnt_root;
nd->state |= ND_JUMPED;
nd->next_seq = read_seqcount_begin(&dentry->d_seq);
*inode = dentry->d_inode;
/*
* We don't need to re-check ->d_seq after this
* ->d_inode read - there will be an RCU delay
* between mount hash removal and ->mnt_root
* becoming unpinned.
*/
flags = dentry->d_flags;
// makes sure that non-RCU pathwalk could reach
// this state.
@ -1527,7 +1519,7 @@ static bool __follow_mount_rcu(struct nameidata *nd, struct path *path,
}
static inline int handle_mounts(struct nameidata *nd, struct dentry *dentry,
struct path *path, struct inode **inode)
struct path *path)
{
bool jumped;
int ret;
@ -1536,12 +1528,7 @@ static inline int handle_mounts(struct nameidata *nd, struct dentry *dentry,
path->dentry = dentry;
if (nd->flags & LOOKUP_RCU) {
unsigned int seq = nd->next_seq;
*inode = dentry->d_inode;
if (read_seqcount_retry(&dentry->d_seq, seq))
return -ECHILD;
if (unlikely(!*inode))
return -ENOENT;
if (likely(__follow_mount_rcu(nd, path, inode)))
if (likely(__follow_mount_rcu(nd, path)))
return 0;
// *path and nd->next_seq might've been clobbered
path->mnt = nd->path.mnt;
@ -1561,8 +1548,6 @@ static inline int handle_mounts(struct nameidata *nd, struct dentry *dentry,
dput(path->dentry);
if (path->mnt != nd->path.mnt)
mntput(path->mnt);
} else {
*inode = d_backing_inode(path->dentry);
}
return ret;
}
@ -1843,15 +1828,21 @@ static const char *step_into(struct nameidata *nd, int flags,
{
struct path path;
struct inode *inode;
int err = handle_mounts(nd, dentry, &path, &inode);
int err = handle_mounts(nd, dentry, &path);
if (err < 0)
return ERR_PTR(err);
inode = path.dentry->d_inode;
if (likely(!d_is_symlink(path.dentry)) ||
((flags & WALK_TRAILING) && !(nd->flags & LOOKUP_FOLLOW)) ||
(flags & WALK_NOFOLLOW)) {
/* not a symlink or should not follow */
if (!(nd->flags & LOOKUP_RCU)) {
if (nd->flags & LOOKUP_RCU) {
if (read_seqcount_retry(&path.dentry->d_seq, nd->next_seq))
return ERR_PTR(-ECHILD);
if (unlikely(!inode))
return ERR_PTR(-ENOENT);
} else {
dput(nd->path.dentry);
if (nd->path.mnt != path.mnt)
mntput(nd->path.mnt);