diff --git a/fs/namei.c b/fs/namei.c index 07c00ade4c1a578625e6772e9e2a2e590b36639a..98e24fdb22c10cd7008b994274ffc5bf4fe52aaa 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -691,6 +691,8 @@ static bool try_to_unlazy(struct nameidata *nd) BUG_ON(!(nd->flags & LOOKUP_RCU)); nd->flags &= ~LOOKUP_RCU; + if (nd->flags & LOOKUP_CACHED) + goto out1; if (unlikely(!legitimize_links(nd))) goto out1; if (unlikely(!legitimize_path(nd, &nd->path, nd->seq))) @@ -727,6 +729,8 @@ static int unlazy_child(struct nameidata *nd, struct dentry *dentry, unsigned se BUG_ON(!(nd->flags & LOOKUP_RCU)); nd->flags &= ~LOOKUP_RCU; + if (nd->flags & LOOKUP_CACHED) + goto out2; if (unlikely(!legitimize_links(nd))) goto out2; if (unlikely(!legitimize_mnt(nd->path.mnt, nd->m_seq))) @@ -798,6 +802,7 @@ static int complete_walk(struct nameidata *nd) if (!(nd->state & ND_ROOT_PRESET)) if (!(nd->flags & LOOKUP_IS_SCOPED)) nd->root.mnt = NULL; + nd->flags &= ~LOOKUP_CACHED; if (!try_to_unlazy(nd)) return -ECHILD; } @@ -2210,6 +2215,10 @@ static const char *path_init(struct nameidata *nd, unsigned flags) int error; const char *s = nd->name->name; + /* LOOKUP_CACHED requires RCU, ask caller to retry */ + if ((flags & (LOOKUP_RCU | LOOKUP_CACHED)) == LOOKUP_CACHED) + return ERR_PTR(-EAGAIN); + if (!*s) flags &= ~LOOKUP_RCU; if (flags & LOOKUP_RCU) diff --git a/include/linux/namei.h b/include/linux/namei.h index ca94eb5d2b16676fc999e649357c569bdfe3cb13..be9a2b349ca7e80e003f4ce86bd2512a928f1494 100644 --- a/include/linux/namei.h +++ b/include/linux/namei.h @@ -43,6 +43,7 @@ enum {LAST_NORM, LAST_ROOT, LAST_DOT, LAST_DOTDOT}; #define LOOKUP_NO_XDEV 0x040000 /* No mountpoint crossing. */ #define LOOKUP_BENEATH 0x080000 /* No escaping from starting point. */ #define LOOKUP_IN_ROOT 0x100000 /* Treat dirfd as fs root. */ +#define LOOKUP_CACHED 0x200000 /* Only do cached lookup */ /* LOOKUP_* flags which do scope-related checks based on the dirfd. */ #define LOOKUP_IS_SCOPED (LOOKUP_BENEATH | LOOKUP_IN_ROOT)