From: Jens Axboe axboe@kernel.dk
[ Upstream commit 99668f618062816ca7ba639b007eb145b9d3d41e ]
Now that we support non-blocking path resolution internally, expose it via openat2() in the struct open_how ->resolve flags. This allows applications using openat2() to limit path resolution to the extent that it is already cached.
If the lookup cannot be satisfied in a non-blocking manner, openat2(2) will return -1/-EAGAIN.
Cc: Al Viro viro@zeniv.linux.org.uk Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Al Viro viro@zeniv.linux.org.uk Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/open.c | 6 ++++++ include/linux/fcntl.h | 2 +- include/uapi/linux/openat2.h | 4 ++++ 3 files changed, 11 insertions(+), 1 deletion(-)
--- a/fs/open.c +++ b/fs/open.c @@ -1099,6 +1099,12 @@ inline int build_open_flags(const struct lookup_flags |= LOOKUP_BENEATH; if (how->resolve & RESOLVE_IN_ROOT) lookup_flags |= LOOKUP_IN_ROOT; + if (how->resolve & RESOLVE_CACHED) { + /* Don't bother even trying for create/truncate/tmpfile open */ + if (flags & (O_TRUNC | O_CREAT | O_TMPFILE)) + return -EAGAIN; + lookup_flags |= LOOKUP_CACHED; + }
op->lookup_flags = lookup_flags; return 0; --- a/include/linux/fcntl.h +++ b/include/linux/fcntl.h @@ -19,7 +19,7 @@ /* List of all valid flags for the how->resolve argument: */ #define VALID_RESOLVE_FLAGS \ (RESOLVE_NO_XDEV | RESOLVE_NO_MAGICLINKS | RESOLVE_NO_SYMLINKS | \ - RESOLVE_BENEATH | RESOLVE_IN_ROOT) + RESOLVE_BENEATH | RESOLVE_IN_ROOT | RESOLVE_CACHED)
/* List of all open_how "versions". */ #define OPEN_HOW_SIZE_VER0 24 /* sizeof first published struct */ --- a/include/uapi/linux/openat2.h +++ b/include/uapi/linux/openat2.h @@ -35,5 +35,9 @@ struct open_how { #define RESOLVE_IN_ROOT 0x10 /* Make all jumps to "/" and ".." be scoped inside the dirfd (similar to chroot(2)). */ +#define RESOLVE_CACHED 0x20 /* Only complete if resolution can be + completed through cached lookup. May + return -EAGAIN if that's not + possible. */
#endif /* _UAPI_LINUX_OPENAT2_H */