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@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
---
fs/open.c | 6 ++++++
include/linux/fcntl.h | 2 +-
include/uapi/linux/openat2.h | 4 ++++
3 files changed, 11 insertions(+), 1 deletion(-)
diff --git a/fs/open.c b/fs/open.c
index 1e06e443a565..ca5444733acd 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -1091,6 +1091,12 @@ inline int build_open_flags(const struct open_how *how, struct open_flags *op)
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;
diff --git a/include/linux/fcntl.h b/include/linux/fcntl.h
index 921e750843e6..766fcd973beb 100644
--- 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 */
diff --git a/include/uapi/linux/openat2.h b/include/uapi/linux/openat2.h
index 58b1eb711360..a5feb7604948 100644
--- 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 */
--
2.29.2
