From 16b1c1cd71176ab0a76b26818fbf12db9183ed57 Mon Sep 17 00:00:00 2001 From: Miklos Szeredi Date: Mon, 21 May 2012 17:30:19 +0200 Subject: vfs: retry last component if opening stale dentry NFS optimizes away d_revalidates for last component of open. This means that open itself can find the dentry stale. This patch allows the filesystem to return EOPENSTALE and the VFS will retry the lookup on just the last component if possible. If the lookup was done using RCU mode, including the last component, then this is not possible since the parent dentry is lost. In this case fall back to non-RCU lookup. Currently this is not used since NFS will always leave RCU mode. Signed-off-by: Miklos Szeredi Signed-off-by: Al Viro --- fs/namei.c | 37 +++++++++++++++++++++++++++++++++++-- 1 file changed, 35 insertions(+), 2 deletions(-) (limited to 'fs') diff --git a/fs/namei.c b/fs/namei.c index 998d5316921a..7d694194024a 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -2202,6 +2202,8 @@ static struct file *do_last(struct nameidata *nd, struct path *path, struct file *filp; struct inode *inode; int symlink_ok = 0; + struct path save_parent = { .dentry = NULL, .mnt = NULL }; + bool retried = false; int error; nd->flags &= ~LOOKUP_PARENT; @@ -2267,6 +2269,7 @@ static struct file *do_last(struct nameidata *nd, struct path *path, if (nd->last.name[nd->last.len]) goto exit; +retry_lookup: mutex_lock(&dir->d_inode->i_mutex); dentry = lookup_hash(nd); @@ -2349,12 +2352,21 @@ finish_lookup: return NULL; } - path_to_nameidata(path, nd); + if ((nd->flags & LOOKUP_RCU) || nd->path.mnt != path->mnt) { + path_to_nameidata(path, nd); + } else { + save_parent.dentry = nd->path.dentry; + save_parent.mnt = mntget(path->mnt); + nd->path.dentry = path->dentry; + + } nd->inode = inode; /* Why this, you ask? _Now_ we might have grown LOOKUP_JUMPED... */ error = complete_walk(nd); - if (error) + if (error) { + path_put(&save_parent); return ERR_PTR(error); + } error = -EISDIR; if ((open_flag & O_CREAT) && S_ISDIR(nd->inode->i_mode)) goto exit; @@ -2377,6 +2389,20 @@ common: if (error) goto exit; filp = nameidata_to_filp(nd); + if (filp == ERR_PTR(-EOPENSTALE) && save_parent.dentry && !retried) { + BUG_ON(save_parent.dentry != dir); + path_put(&nd->path); + nd->path = save_parent; + nd->inode = dir->d_inode; + save_parent.mnt = NULL; + save_parent.dentry = NULL; + if (want_write) { + mnt_drop_write(nd->path.mnt); + want_write = 0; + } + retried = true; + goto retry_lookup; + } if (!IS_ERR(filp)) { error = ima_file_check(filp, op->acc_mode); if (error) { @@ -2396,6 +2422,7 @@ common: out: if (want_write) mnt_drop_write(nd->path.mnt); + path_put(&save_parent); terminate_walk(nd); return filp; @@ -2459,6 +2486,12 @@ out: if (base) fput(base); release_open_intent(nd); + if (filp == ERR_PTR(-EOPENSTALE)) { + if (flags & LOOKUP_RCU) + filp = ERR_PTR(-ECHILD); + else + filp = ERR_PTR(-ESTALE); + } return filp; out_filp: -- cgit v1.2.3