From 16b1c1cd71176ab0a76b26818fbf12db9183ed57 Mon Sep 17 00:00:00 2001 From: Miklos Szeredi Date: Mon, 21 May 2012 17:30:19 +0200 Subject: [PATCH] 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 +++++++++++++++++++++++++++++++++++-- include/linux/errno.h | 1 + 2 files changed, 36 insertions(+), 2 deletions(-) diff --git a/fs/namei.c b/fs/namei.c index 998d531..7d69419 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: diff --git a/include/linux/errno.h b/include/linux/errno.h index 2d09bfa..e0de516 100644 --- a/include/linux/errno.h +++ b/include/linux/errno.h @@ -17,6 +17,7 @@ #define ENOIOCTLCMD 515 /* No ioctl command */ #define ERESTART_RESTARTBLOCK 516 /* restart by calling sys_restart_syscall */ #define EPROBE_DEFER 517 /* Driver requests probe retry */ +#define EOPENSTALE 518 /* open found a stale dentry */ /* Defined for the NFSv3 protocol */ #define EBADHANDLE 521 /* Illegal NFS file handle */ -- 2.7.4