RESOLVE_CACHED allows an application to attempt a cache-only open of a file. If this isn't possible, the request will fail with -1/EAGAIN and the caller should retry without RESOLVE_CACHED set. This will generally happen from a different context, where a slower open operation can be performed. Signed-off-by: Jens Axboe <axboe@xxxxxxxxx> --- Since v2: - Incorporate suggested edits from Michael diff --git a/man2/openat2.2 b/man2/openat2.2 index 3bda20620574..a8381c753f0d 100644 --- a/man2/openat2.2 +++ b/man2/openat2.2 @@ -385,6 +385,17 @@ This may occur if, for example, a system pathname that is used by an application is modified (e.g., in a new distribution release) so that a pathname component (now) contains a bind mount. +.TP +.B RESOLVE_CACHED +Make the open operation fail unless all path components are already present +in the kernel's lookup cache. +If any kind of revalidation or I/O is needed to satisfy the lookup, +.BR openat2 () +fails with the error +.B EAGAIN . +This is useful in providing a fast-path open that can be performed without +resorting to thread offload, or other mechanisms that an application might +use to offload slower operations. .RE .IP If any bits other than those listed above are set in @@ -421,6 +432,14 @@ The caller may choose to retry the .BR openat2 () call. .TP +.B EAGAIN +.BR RESOLVE_CACHED +was set, and the open operation cannot be performed using only cached +information. The caller should retry without +.B RESOLVE_CACHED +set in +.I how.resolve . +.TP .B EINVAL An unknown flag or invalid value was specified in .IR how . -- Jens Axboe
