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massage __follow_mount_rcu() a bit 

make the loop more similar to that in follow_managed(), with
explicit tracking of flags, etc.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2020-01-16 09:52:04 -05:00
parent c108837e06
commit ea936aeb3e
1 changed files with 35 additions and 35 deletions
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70
fs/namei.c
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@ -1269,12 +1269,6 @@ int follow_down_one(struct path *path)
}
EXPORT_SYMBOL(follow_down_one);
static inline int managed_dentry_rcu(const struct path *path)
{
return (path->dentry->d_flags & DCACHE_MANAGE_TRANSIT) ?
path->dentry->d_op->d_manage(path, true) : 0;
}
/*
* Try to skip to top of mountpoint pile in rcuwalk mode. Fail if
* we meet a managed dentry that would need blocking.
@ -1282,43 +1276,49 @@ static inline int managed_dentry_rcu(const struct path *path)
static bool __follow_mount_rcu(struct nameidata *nd, struct path *path,
struct inode **inode, unsigned *seqp)
{
struct dentry *dentry = path->dentry;
unsigned int flags = dentry->d_flags;
if (likely(!(flags & DCACHE_MANAGED_DENTRY)))
return true;
if (unlikely(nd->flags & LOOKUP_NO_XDEV))
return false;
for (;;) {
struct mount *mounted;
/*
* Don't forget we might have a non-mountpoint managed dentry
* that wants to block transit.
*/
switch (managed_dentry_rcu(path)) {
case -ECHILD:
default:
return false;
case -EISDIR:
return true;
case 0:
break;
if (unlikely(flags & DCACHE_MANAGE_TRANSIT)) {
int res = dentry->d_op->d_manage(path, true);
if (res)
return res == -EISDIR;
flags = dentry->d_flags;
}
if (!d_mountpoint(path->dentry))
return !(path->dentry->d_flags & DCACHE_NEED_AUTOMOUNT);
mounted = __lookup_mnt(path->mnt, path->dentry);
if (!mounted)
break;
if (unlikely(nd->flags & LOOKUP_NO_XDEV))
return false;
path->mnt = &mounted->mnt;
path->dentry = mounted->mnt.mnt_root;
nd->flags |= LOOKUP_JUMPED;
*seqp = read_seqcount_begin(&path->dentry->d_seq);
/*
* Update the inode too. We don't need to re-check the
* dentry sequence number here after this d_inode read,
* because a mount-point is always pinned.
*/
*inode = path->dentry->d_inode;
if (flags & DCACHE_MOUNTED) {
struct mount *mounted = __lookup_mnt(path->mnt, dentry);
if (mounted) {
path->mnt = &mounted->mnt;
dentry = path->dentry = mounted->mnt.mnt_root;
nd->flags |= LOOKUP_JUMPED;
*seqp = 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;
continue;
}
if (read_seqretry(&mount_lock, nd->m_seq))
return false;
}
return !(flags & DCACHE_NEED_AUTOMOUNT);
}
return !read_seqretry(&mount_lock, nd->m_seq) &&
!(path->dentry->d_flags & DCACHE_NEED_AUTOMOUNT);
}
static inline int handle_mounts(struct nameidata *nd, struct dentry *dentry,