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authorNeilBrown <neilb@suse.de>2014-08-04 17:06:29 +1000
committerAl Viro <viro@zeniv.linux.org.uk>2014-08-07 14:40:10 -0400
commitb8faf035ea9d0011b04856a8198e2e212d93346a (patch)
treefe06d46ee4a2d659f05740e331a8c823d62d5e3a /fs/namei.c
parent7c33d5972ce382bcc506d16235f1e9b7d22cbef8 (diff)
downloadlwn-b8faf035ea9d0011b04856a8198e2e212d93346a.tar.gz
lwn-b8faf035ea9d0011b04856a8198e2e212d93346a.zip
VFS: allow ->d_manage() to declare -EISDIR in rcu_walk mode.
In REF-walk mode, ->d_manage can return -EISDIR to indicate that the dentry is not really a mount trap (or even a mount point) and that any mounts or any DCACHE_NEED_AUTOMOUNT flag should be ignored. RCU-walk mode doesn't currently support this, so if there is a dentry with DCACHE_NEED_AUTOMOUNT set but which shouldn't be a mount-trap, lookup_fast() will always drop in REF-walk mode. With this patch, an -EISDIR from ->d_manage will always cause mounts and automounts to be ignored, both in REF-walk and RCU-walk. Bug-fixed-by: Dan Carpenter <dan.carpenter@oracle.com> Cc: Ian Kent <raven@themaw.net> Signed-off-by: NeilBrown <neilb@suse.de> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'fs/namei.c')
-rw-r--r--fs/namei.c27
1 files changed, 16 insertions, 11 deletions
diff --git a/fs/namei.c b/fs/namei.c
index 0ff23cecb1bb..8a217c48f6db 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1091,10 +1091,10 @@ int follow_down_one(struct path *path)
}
EXPORT_SYMBOL(follow_down_one);
-static inline bool managed_dentry_might_block(struct dentry *dentry)
+static inline int managed_dentry_rcu(struct dentry *dentry)
{
- return (dentry->d_flags & DCACHE_MANAGE_TRANSIT &&
- dentry->d_op->d_manage(dentry, true) < 0);
+ return (dentry->d_flags & DCACHE_MANAGE_TRANSIT) ?
+ dentry->d_op->d_manage(dentry, true) : 0;
}
/*
@@ -1110,11 +1110,18 @@ static bool __follow_mount_rcu(struct nameidata *nd, struct path *path,
* Don't forget we might have a non-mountpoint managed dentry
* that wants to block transit.
*/
- if (unlikely(managed_dentry_might_block(path->dentry)))
+ switch (managed_dentry_rcu(path->dentry)) {
+ case -ECHILD:
+ default:
return false;
+ case -EISDIR:
+ return true;
+ case 0:
+ break;
+ }
if (!d_mountpoint(path->dentry))
- return true;
+ return !(path->dentry->d_flags & DCACHE_NEED_AUTOMOUNT);
mounted = __lookup_mnt(path->mnt, path->dentry);
if (!mounted)
@@ -1130,7 +1137,8 @@ static bool __follow_mount_rcu(struct nameidata *nd, struct path *path,
*/
*inode = path->dentry->d_inode;
}
- return read_seqretry(&mount_lock, nd->m_seq);
+ return read_seqretry(&mount_lock, nd->m_seq) &&
+ !(path->dentry->d_flags & DCACHE_NEED_AUTOMOUNT);
}
static int follow_dotdot_rcu(struct nameidata *nd)
@@ -1402,11 +1410,8 @@ static int lookup_fast(struct nameidata *nd,
}
path->mnt = mnt;
path->dentry = dentry;
- if (unlikely(!__follow_mount_rcu(nd, path, inode)))
- goto unlazy;
- if (unlikely(path->dentry->d_flags & DCACHE_NEED_AUTOMOUNT))
- goto unlazy;
- return 0;
+ if (likely(__follow_mount_rcu(nd, path, inode)))
+ return 0;
unlazy:
if (unlazy_walk(nd, dentry))
return -ECHILD;