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vfs - check non-mountpoint dentry might block in __follow_mount_rcu()

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When following a mount in rcu-walk mode we must check if the incoming dentry
is telling us it may need to block, even if it isn't actually a mountpoint.

Signed-off-by: Ian Kent <raven@themaw.net>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Ian Kent 2011-03-25 01:51:02 +08:00 committed by Al Viro
parent b81a618dcd
commit 62a7375e5d
1 changed files with 18 additions and 5 deletions
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23
fs/namei.c
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@ -992,6 +992,12 @@ int follow_down_one(struct path *path)
return 0; return 0;
} }
static inline bool managed_dentry_might_block(struct dentry *dentry)
{
return (dentry->d_flags & DCACHE_MANAGE_TRANSIT &&
dentry->d_op->d_manage(dentry, true) < 0);
}
/* /*
* Skip to top of mountpoint pile in rcuwalk mode. We abort the rcu-walk if we * Skip to top of mountpoint pile in rcuwalk mode. We abort the rcu-walk if we
* meet a managed dentry and we're not walking to "..". True is returned to * meet a managed dentry and we're not walking to "..". True is returned to
@ -1000,19 +1006,26 @@ int follow_down_one(struct path *path)
static bool __follow_mount_rcu(struct nameidata *nd, struct path *path, static bool __follow_mount_rcu(struct nameidata *nd, struct path *path,
struct inode **inode, bool reverse_transit) struct inode **inode, bool reverse_transit)
{ {
while (d_mountpoint(path->dentry)) { for (;;) {
struct vfsmount *mounted; struct vfsmount *mounted;
if (unlikely(path->dentry->d_flags & DCACHE_MANAGE_TRANSIT) && /*
!reverse_transit && * Don't forget we might have a non-mountpoint managed dentry
path->dentry->d_op->d_manage(path->dentry, true) < 0) * that wants to block transit.
*/
*inode = path->dentry->d_inode;
if (!reverse_transit &&
unlikely(managed_dentry_might_block(path->dentry)))
return false; return false;
if (!d_mountpoint(path->dentry))
break;
mounted = __lookup_mnt(path->mnt, path->dentry, 1); mounted = __lookup_mnt(path->mnt, path->dentry, 1);
if (!mounted) if (!mounted)
break; break;
path->mnt = mounted; path->mnt = mounted;
path->dentry = mounted->mnt_root; path->dentry = mounted->mnt_root;
nd->seq = read_seqcount_begin(&path->dentry->d_seq); nd->seq = read_seqcount_begin(&path->dentry->d_seq);
*inode = path->dentry->d_inode;
} }
if (unlikely(path->dentry->d_flags & DCACHE_NEED_AUTOMOUNT)) if (unlikely(path->dentry->d_flags & DCACHE_NEED_AUTOMOUNT))