If LOOKUP_RCU is set, follow_link will not take/drop reference counts. Replace cond_resched() with _cond_resched() as the latter is a no-op if rcu_read_lock() is held while the former will give a warning in that case.
After taking a copy of dentry->d_inode, check d_seq to ensure this is still the symlink we were looking for. Signed-off-by: NeilBrown <[email protected]> --- fs/namei.c | 27 +++++++++++++++++++-------- 1 file changed, 19 insertions(+), 8 deletions(-) diff --git a/fs/namei.c b/fs/namei.c index 72f5a4f91855..40ff4cb04244 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -897,16 +897,21 @@ follow_link(struct path *link, struct nameidata *nd, void **p) char *s; nd->flags &= ~LOOKUP_LINK_RCU; - if (nd->flags & LOOKUP_RCU) + if (nd->flags & LOOKUP_RCU) { nd->flags |= LOOKUP_LINK_RCU; - else if (link->mnt == nd->path.mnt) + if (__read_seqcount_retry(&dentry->d_seq, nd->seq)) { + error = -ECHILD; + goto out_put_nd_path; + } + } else if (link->mnt == nd->path.mnt) mntget(link->mnt); error = -ELOOP; if (unlikely(nd->total_link_count >= 40)) goto out_put_nd_path; - cond_resched(); + /* If rcu_read_locked(), this will not resched, and will not warn */ + _cond_resched(); nd->total_link_count++; if (nd->flags & LOOKUP_RCU) { @@ -938,11 +943,17 @@ follow_link(struct path *link, struct nameidata *nd, void **p) return PTR_ERR(s); } if (*s == '/') { - if (!nd->root.mnt) - set_root(nd); - path_put(&nd->path); - nd->path = nd->root; - path_get(&nd->root); + if (nd->flags & LOOKUP_RCU) { + if (!nd->root.mnt) + set_root_rcu(nd); + nd->path = nd->root; + } else { + if (!nd->root.mnt) + set_root(nd); + path_put(&nd->path); + nd->path = nd->root; + path_get(&nd->root); + } nd->flags |= LOOKUP_JUMPED; } nd->inode = nd->path.dentry->d_inode; -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
