On 12/23/20 5:41 AM, Michael Kerrisk (man-pages) wrote: > Hi Jens, > > On 12/17/20 10:18 PM, Jens Axboe wrote: >> 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> > > I take it that this feature is not yet merged into the kernel? > (At least, I couldn't grep RESOLVE_CACHED in current > kernel sources.) Right - see the email thread linked in the posting. Should be landing in 5.12 though, and I just wanted to hash out the details of the man page upfront so it'd be ready to go as well. Sorry if that wasn't 100% clear! >> First attempt at this, fully expecting the phrasing to require some >> massaging. >> >> Also see: https://lore.kernel.org/linux-fsdevel/20201217161911.743222-1-axboe@xxxxxxxxx/T/ >> >> diff --git a/man2/openat2.2 b/man2/openat2.2 >> index 3bda20620574..282c13e2df96 100644 >> --- a/man2/openat2.2 >> +++ b/man2/openat2.2 >> @@ -385,6 +385,15 @@ 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 >> +Fail path resolution, unless all components needed already exist in the > > I think "Fail path resolution" needs some clarification. > > Maybe something like: > [[ > Make the open operation fail unless all path components > are already present in the kernel's lookup cache. > ]] > ? That is cleared indeed, I'll rephrase that one. >> +lookup cache. If any kind of revalidation or IO is needed to satisfy the > ^ > Please start new sentences on new lines. Using such-called "semantic > newlines" makes for cleaner future patches. OK >> +lookup, then fail the open attempt with > > "fail the open attempt with" > ==> > .BR openat2 () > fails with the error Fixed up >> +.B EAGAIN. >> +This is useful in providing a fast path open that can be performed without >> +resorting to thread offload, or other mechanism that an application might >> +use to offload slower operations. >> .RE >> .IP >> If any bits other than those listed above are set in >> @@ -421,6 +430,14 @@ 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 cached. The caller should > > semantic newline OK Thanks Michael, I'll make the edits. -- Jens Axboe
