* [PATCH v2] man2/openat2.2: add RESOLVE_CACHED
@ 2021-02-20 19:17 Jens Axboe
2021-02-21 9:04 ` Michael Kerrisk (man-pages)
0 siblings, 1 reply; 3+ messages in thread
From: Jens Axboe @ 2021-02-20 19:17 UTC (permalink / raw
To: linux-man, Michael Kerrisk-manpages
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@kernel.dk>
---
Sending a v2 of this one, as the kernel side patches are queued up
for 5.12 inclusion.
diff --git a/man2/openat2.2 b/man2/openat2.2
index 3bda20620574..37e70c43de6d 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 kernels 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 cached.
+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
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH v2] man2/openat2.2: add RESOLVE_CACHED
2021-02-20 19:17 [PATCH v2] man2/openat2.2: add RESOLVE_CACHED Jens Axboe
@ 2021-02-21 9:04 ` Michael Kerrisk (man-pages)
2021-02-21 13:11 ` Jens Axboe
0 siblings, 1 reply; 3+ messages in thread
From: Michael Kerrisk (man-pages) @ 2021-02-21 9:04 UTC (permalink / raw
To: Jens Axboe, linux-man; +Cc: mtk.manpages
Hello Jens
Thanks for the revised patch. Just some minor comments below.
On 2/20/21 8:17 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@kernel.dk>
>
> ---
>
> Sending a v2 of this one, as the kernel side patches are queued up
> for 5.12 inclusion.
>
> diff --git a/man2/openat2.2 b/man2/openat2.2
> index 3bda20620574..37e70c43de6d 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 kernels lookup cache.
s/kernels/kernel's/
> +If any kind of revalidation or I/O is needed to satisfy the lookup,
> +.BR openat2 ()
> +fails with the error
> +.B EAGAIN.
.BR EAGAIN .
> +This is useful in providing a fast path open that can be performed without
s/fast path open/fast-path open/
> +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 cached.
Maybe:
s/cached
/using only cached information/
?
> +The caller should retry without
> +.B RESOLVE_CACHED
> +set in
> +.I how.resolve
.IR how.resolve .
> +.TP
> .B EINVAL
> An unknown flag or invalid value was specified in
> .IR how .
Thanks,
Michael
--
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH v2] man2/openat2.2: add RESOLVE_CACHED
2021-02-21 9:04 ` Michael Kerrisk (man-pages)
@ 2021-02-21 13:11 ` Jens Axboe
0 siblings, 0 replies; 3+ messages in thread
From: Jens Axboe @ 2021-02-21 13:11 UTC (permalink / raw
To: Michael Kerrisk (man-pages), linux-man
On 2/21/21 2:04 AM, Michael Kerrisk (man-pages) wrote:
> Hello Jens
>
> Thanks for the revised patch. Just some minor comments below.
Thanks, all look good to me. I'll send out v3.
--
Jens Axboe
^ permalink raw reply [flat|nested] 3+ messages in thread
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2021-02-20 19:17 [PATCH v2] man2/openat2.2: add RESOLVE_CACHED Jens Axboe
2021-02-21 9:04 ` Michael Kerrisk (man-pages)
2021-02-21 13:11 ` Jens Axboe
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