* [PATCH] prctl.2: doc PR_SET/GET_IO_FLUSHER - V4
@ 2020-04-02 2:08 Mike Christie
2020-04-02 3:46 ` Bart Van Assche
` (2 more replies)
0 siblings, 3 replies; 10+ messages in thread
From: Mike Christie @ 2020-04-02 2:08 UTC (permalink / raw)
To: linux-api, david, mhocko, masato.suzuki, damien.lemoal,
darrick.wong, bvanassche, mtk.manpages, linux-man
Cc: Mike Christie
This patch documents the PR_SET_IO_FLUSHER and PR_GET_IO_FLUSHER
prctl commands added to the linux kernel for 5.6 in commit:
commit 8d19f1c8e1937baf74e1962aae9f90fa3aeab463
Author: Mike Christie <mchristi@redhat.com>
Date: Mon Nov 11 18:19:00 2019 -0600
prctl: PR_{G,S}ET_IO_FLUSHER to support controlling memory reclaim
Signed-off-by: Mike Christie <mchristi@redhat.com>
---
V4:
- Remove internal details.
- Add CAP_SYS_RESOURCE requirement info.
V3:
- Replace emulation device example.
V2:
- My initial patch for this was very bad. This version is almost 100%
taken word for word from Dave Chinner's review comments.
Signed-off-by: Mike Christie <mchristi@redhat.com>
man2/prctl.2 | 26 ++++++++++++++++++++++++++
1 file changed, 26 insertions(+)
diff --git a/man2/prctl.2 b/man2/prctl.2
index 720ec04e4..3c3355439 100644
--- a/man2/prctl.2
+++ b/man2/prctl.2
@@ -1381,6 +1381,31 @@ system call on Tru64).
for information on versions and architectures.)
Return unaligned access control bits, in the location pointed to by
.IR "(unsigned int\ *) arg2" .
+.TP
+.B PR_SET_IO_FLUSHER (Since Linux 5.6)
+If a user process is involved in the block layer or file system IO path,
+and can allocate memory while processing IO requests it must set
+\fIarg2\fP to 1. This will put the process in the IO_FLUSHER state which
+allows it special treatment to make progress when allocating memory.
+If \fIarg2\fP is 0, the process will clear the IO_FLUSHER state, and
+the default behavior will be used.
+
+The calling process must have the
+.BR CAP_SYS_RESOURCE
+capability.
+
+Examples of IO_FLUSHER applications are FUSE daemons, SCSI device
+emulation daemons, and daemons that perform error handling like multipath
+path recovery applications.
+
+.TP
+.B PR_GET_IO_FLUSHER (Since Linux 5.6)
+Return as the function result 1 if the caller is in the IO_FLUSHER state and
+0 if not.
+
+The calling process must have the
+.BR CAP_SYS_RESOURCE
+capability.
.SH RETURN VALUE
On success,
.BR PR_GET_DUMPABLE ,
@@ -1395,6 +1420,7 @@ On success,
.BR PR_GET_SPECULATION_CTRL ,
.BR PR_MCE_KILL_GET ,
.BR PR_CAP_AMBIENT + PR_CAP_AMBIENT_IS_SET ,
+.BR PR_GET_IO_FLUSHER ,
and (if it returns)
.BR PR_GET_SECCOMP
return the nonnegative values described above.
--
2.21.0
^ permalink raw reply related [flat|nested] 10+ messages in thread* Re: [PATCH] prctl.2: doc PR_SET/GET_IO_FLUSHER - V4
2020-04-02 2:08 [PATCH] prctl.2: doc PR_SET/GET_IO_FLUSHER - V4 Mike Christie
@ 2020-04-02 3:46 ` Bart Van Assche
2020-04-02 12:16 ` Michael Kerrisk (man-pages)
2020-04-02 14:01 ` Michael Christie
2020-04-02 6:47 ` Michal Hocko
2020-04-02 12:16 ` Michael Kerrisk (man-pages)
2 siblings, 2 replies; 10+ messages in thread
From: Bart Van Assche @ 2020-04-02 3:46 UTC (permalink / raw)
To: Mike Christie, linux-api, david, mhocko, masato.suzuki,
damien.lemoal, darrick.wong, mtk.manpages, linux-man
On 2020-04-01 19:08, Mike Christie wrote:
> +.TP
> +.B PR_GET_IO_FLUSHER (Since Linux 5.6)
> +Return as the function result 1 if the caller is in the IO_FLUSHER state and
> +0 if not.
Although I'm not at all a language expert, the word order at the start
of the above sentence seems a bit weird to me?
Thanks,
Bart.
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH] prctl.2: doc PR_SET/GET_IO_FLUSHER - V4
2020-04-02 3:46 ` Bart Van Assche
@ 2020-04-02 12:16 ` Michael Kerrisk (man-pages)
2020-04-02 14:01 ` Michael Christie
1 sibling, 0 replies; 10+ messages in thread
From: Michael Kerrisk (man-pages) @ 2020-04-02 12:16 UTC (permalink / raw)
To: Bart Van Assche, Mike Christie, linux-api, david, mhocko,
masato.suzuki, damien.lemoal, darrick.wong, linux-man
Cc: mtk.manpages
On 4/2/20 5:46 AM, Bart Van Assche wrote:
> On 2020-04-01 19:08, Mike Christie wrote:
>> +.TP
>> +.B PR_GET_IO_FLUSHER (Since Linux 5.6)
>> +Return as the function result 1 if the caller is in the IO_FLUSHER state and
>> +0 if not.
>
> Although I'm not at all a language expert, the word order at the start
> of the above sentence seems a bit weird to me?
Thanks for spotting that Bart. I changed the text to:
If a user process is involved in the block layer or
filesystem I/O path, and can allocate memory while process‐
ing I/O requests it must set arg2 to 1. This will put the
process in the IO_FLUSHER state, which allows it special
treatment to make progress when allocating memory. If arg2
is 0, the process will clear the IO_FLUSHER state, and the
default behavior will be used.
Cheers,
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] 10+ messages in thread* Re: [PATCH] prctl.2: doc PR_SET/GET_IO_FLUSHER - V4
2020-04-02 3:46 ` Bart Van Assche
2020-04-02 12:16 ` Michael Kerrisk (man-pages)
@ 2020-04-02 14:01 ` Michael Christie
2020-04-02 20:12 ` Michael Kerrisk (man-pages)
1 sibling, 1 reply; 10+ messages in thread
From: Michael Christie @ 2020-04-02 14:01 UTC (permalink / raw)
To: Bart Van Assche, linux-api, david, mhocko, masato.suzuki,
damien.lemoal, darrick.wong, mtk.manpages, linux-man
On 04/01/2020 10:46 PM, Bart Van Assche wrote:
> On 2020-04-01 19:08, Mike Christie wrote:
>> +.TP
>> +.B PR_GET_IO_FLUSHER (Since Linux 5.6)
>> +Return as the function result 1 if the caller is in the IO_FLUSHER state and
>> +0 if not.
>
> Although I'm not at all a language expert, the word order at the start
> of the above sentence seems a bit weird to me?
>
Do you mean the "Return as the function result" part or something else?
That is how the other commands worded it. It looks like I messed up and
dropped the (). This is how they did it:
"Return (as the function result)"
I will resend with that fix.
If I misunderstood you I will fix that too.
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH] prctl.2: doc PR_SET/GET_IO_FLUSHER - V4
2020-04-02 14:01 ` Michael Christie
@ 2020-04-02 20:12 ` Michael Kerrisk (man-pages)
0 siblings, 0 replies; 10+ messages in thread
From: Michael Kerrisk (man-pages) @ 2020-04-02 20:12 UTC (permalink / raw)
To: Mike Christie
Cc: Bart Van Assche, Linux API, Dave Chinner, Michal Hocko,
masato.suzuki, damien.lemoal, Darrick J. Wong, linux-man
On Thu, 2 Apr 2020 at 16:01, Michael Christie <mchristi@redhat.com> wrote:
>
> On 04/01/2020 10:46 PM, Bart Van Assche wrote:
> > On 2020-04-01 19:08, Mike Christie wrote:
> >> +.TP
> >> +.B PR_GET_IO_FLUSHER (Since Linux 5.6)
> >> +Return as the function result 1 if the caller is in the IO_FLUSHER state and
> >> +0 if not.
> >
> > Although I'm not at all a language expert, the word order at the start
> > of the above sentence seems a bit weird to me?
> >
>
> Do you mean the "Return as the function result" part or something else?
>
> That is how the other commands worded it. It looks like I messed up and
> dropped the (). This is how they did it:
>
> "Return (as the function result)"
>
> I will resend with that fix.
>
> If I misunderstood you I will fix that too.
I already fixed this piece. There are still the open questions in my
other mail though.
--
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] 10+ messages in thread
* Re: [PATCH] prctl.2: doc PR_SET/GET_IO_FLUSHER - V4
2020-04-02 2:08 [PATCH] prctl.2: doc PR_SET/GET_IO_FLUSHER - V4 Mike Christie
2020-04-02 3:46 ` Bart Van Assche
@ 2020-04-02 6:47 ` Michal Hocko
2020-04-02 12:16 ` Michael Kerrisk (man-pages)
2020-04-02 12:16 ` Michael Kerrisk (man-pages)
2 siblings, 1 reply; 10+ messages in thread
From: Michal Hocko @ 2020-04-02 6:47 UTC (permalink / raw)
To: Mike Christie
Cc: linux-api, david, masato.suzuki, damien.lemoal, darrick.wong,
bvanassche, mtk.manpages, linux-man
On Wed 01-04-20 21:08:50, Mike Christie wrote:
> This patch documents the PR_SET_IO_FLUSHER and PR_GET_IO_FLUSHER
> prctl commands added to the linux kernel for 5.6 in commit:
>
> commit 8d19f1c8e1937baf74e1962aae9f90fa3aeab463
> Author: Mike Christie <mchristi@redhat.com>
> Date: Mon Nov 11 18:19:00 2019 -0600
>
> prctl: PR_{G,S}ET_IO_FLUSHER to support controlling memory reclaim
>
> Signed-off-by: Mike Christie <mchristi@redhat.com>
Yes this wording is much better than the previous version.
Acked-by: Michal Hocko <mhocko@suse.com>
> ---
>
> V4:
> - Remove internal details.
> - Add CAP_SYS_RESOURCE requirement info.
>
> V3:
> - Replace emulation device example.
>
> V2:
> - My initial patch for this was very bad. This version is almost 100%
> taken word for word from Dave Chinner's review comments.
>
> Signed-off-by: Mike Christie <mchristi@redhat.com>
>
> man2/prctl.2 | 26 ++++++++++++++++++++++++++
> 1 file changed, 26 insertions(+)
>
> diff --git a/man2/prctl.2 b/man2/prctl.2
> index 720ec04e4..3c3355439 100644
> --- a/man2/prctl.2
> +++ b/man2/prctl.2
> @@ -1381,6 +1381,31 @@ system call on Tru64).
> for information on versions and architectures.)
> Return unaligned access control bits, in the location pointed to by
> .IR "(unsigned int\ *) arg2" .
> +.TP
> +.B PR_SET_IO_FLUSHER (Since Linux 5.6)
> +If a user process is involved in the block layer or file system IO path,
> +and can allocate memory while processing IO requests it must set
> +\fIarg2\fP to 1. This will put the process in the IO_FLUSHER state which
> +allows it special treatment to make progress when allocating memory.
> +If \fIarg2\fP is 0, the process will clear the IO_FLUSHER state, and
> +the default behavior will be used.
> +
> +The calling process must have the
> +.BR CAP_SYS_RESOURCE
> +capability.
> +
> +Examples of IO_FLUSHER applications are FUSE daemons, SCSI device
> +emulation daemons, and daemons that perform error handling like multipath
> +path recovery applications.
> +
> +.TP
> +.B PR_GET_IO_FLUSHER (Since Linux 5.6)
> +Return as the function result 1 if the caller is in the IO_FLUSHER state and
> +0 if not.
> +
> +The calling process must have the
> +.BR CAP_SYS_RESOURCE
> +capability.
> .SH RETURN VALUE
> On success,
> .BR PR_GET_DUMPABLE ,
> @@ -1395,6 +1420,7 @@ On success,
> .BR PR_GET_SPECULATION_CTRL ,
> .BR PR_MCE_KILL_GET ,
> .BR PR_CAP_AMBIENT + PR_CAP_AMBIENT_IS_SET ,
> +.BR PR_GET_IO_FLUSHER ,
> and (if it returns)
> .BR PR_GET_SECCOMP
> return the nonnegative values described above.
> --
> 2.21.0
--
Michal Hocko
SUSE Labs
^ permalink raw reply [flat|nested] 10+ messages in thread* Re: [PATCH] prctl.2: doc PR_SET/GET_IO_FLUSHER - V4
2020-04-02 6:47 ` Michal Hocko
@ 2020-04-02 12:16 ` Michael Kerrisk (man-pages)
0 siblings, 0 replies; 10+ messages in thread
From: Michael Kerrisk (man-pages) @ 2020-04-02 12:16 UTC (permalink / raw)
To: Michal Hocko, Mike Christie
Cc: mtk.manpages, linux-api, david, masato.suzuki, damien.lemoal,
darrick.wong, bvanassche, linux-man
On 4/2/20 8:47 AM, Michal Hocko wrote:
> On Wed 01-04-20 21:08:50, Mike Christie wrote:
>> This patch documents the PR_SET_IO_FLUSHER and PR_GET_IO_FLUSHER
>> prctl commands added to the linux kernel for 5.6 in commit:
>>
>> commit 8d19f1c8e1937baf74e1962aae9f90fa3aeab463
>> Author: Mike Christie <mchristi@redhat.com>
>> Date: Mon Nov 11 18:19:00 2019 -0600
>>
>> prctl: PR_{G,S}ET_IO_FLUSHER to support controlling memory reclaim
>>
>> Signed-off-by: Mike Christie <mchristi@redhat.com>
>
> Yes this wording is much better than the previous version.
>
> Acked-by: Michal Hocko <mhocko@suse.com>
Thanks for the review, Michal!
--
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] 10+ messages in thread
* Re: [PATCH] prctl.2: doc PR_SET/GET_IO_FLUSHER - V4
2020-04-02 2:08 [PATCH] prctl.2: doc PR_SET/GET_IO_FLUSHER - V4 Mike Christie
2020-04-02 3:46 ` Bart Van Assche
2020-04-02 6:47 ` Michal Hocko
@ 2020-04-02 12:16 ` Michael Kerrisk (man-pages)
2020-04-04 21:07 ` Mike Christie
2 siblings, 1 reply; 10+ messages in thread
From: Michael Kerrisk (man-pages) @ 2020-04-02 12:16 UTC (permalink / raw)
To: Mike Christie, linux-api, david, mhocko, masato.suzuki,
damien.lemoal, darrick.wong, bvanassche, linux-man
Cc: mtk.manpages
Hello Mike,
On 4/2/20 4:08 AM, Mike Christie wrote:
> This patch documents the PR_SET_IO_FLUSHER and PR_GET_IO_FLUSHER
> prctl commands added to the linux kernel for 5.6 in commit:
>
> commit 8d19f1c8e1937baf74e1962aae9f90fa3aeab463
> Author: Mike Christie <mchristi@redhat.com>
> Date: Mon Nov 11 18:19:00 2019 -0600>
> prctl: PR_{G,S}ET_IO_FLUSHER to support controlling memory reclaim
>
> Signed-off-by: Mike Christie <mchristi@redhat.com>
I've applied this patch, but I have some questions:
(a) What happens to the IO_FLUSHER setting in the child of fork(2)?
(b) What happens to the IO_FLUSHER setting during an execve(2)?
(Is it preserved, reset, something else?)
Thanks,
Michael
> ---
>
> V4:
> - Remove internal details.
> - Add CAP_SYS_RESOURCE requirement info.
>
> V3:
> - Replace emulation device example.
>
> V2:
> - My initial patch for this was very bad. This version is almost 100%
> taken word for word from Dave Chinner's review comments.
>
> Signed-off-by: Mike Christie <mchristi@redhat.com>
>
> man2/prctl.2 | 26 ++++++++++++++++++++++++++
> 1 file changed, 26 insertions(+)
>
> diff --git a/man2/prctl.2 b/man2/prctl.2
> index 720ec04e4..3c3355439 100644
> --- a/man2/prctl.2
> +++ b/man2/prctl.2
> @@ -1381,6 +1381,31 @@ system call on Tru64).
> for information on versions and architectures.)
> Return unaligned access control bits, in the location pointed to by
> .IR "(unsigned int\ *) arg2" .
> +.TP
> +.B PR_SET_IO_FLUSHER (Since Linux 5.6)
> +If a user process is involved in the block layer or file system IO path,
> +and can allocate memory while processing IO requests it must set
> +\fIarg2\fP to 1. This will put the process in the IO_FLUSHER state which
> +allows it special treatment to make progress when allocating memory.
> +If \fIarg2\fP is 0, the process will clear the IO_FLUSHER state, and
> +the default behavior will be used.
> +
> +The calling process must have the
> +.BR CAP_SYS_RESOURCE
> +capability.
> +
> +Examples of IO_FLUSHER applications are FUSE daemons, SCSI device
> +emulation daemons, and daemons that perform error handling like multipath
> +path recovery applications.
> +
> +.TP
> +.B PR_GET_IO_FLUSHER (Since Linux 5.6)
> +Return as the function result 1 if the caller is in the IO_FLUSHER state and
> +0 if not.
> +
> +The calling process must have the
> +.BR CAP_SYS_RESOURCE
> +capability.
> .SH RETURN VALUE
> On success,
> .BR PR_GET_DUMPABLE ,
> @@ -1395,6 +1420,7 @@ On success,
> .BR PR_GET_SPECULATION_CTRL ,
> .BR PR_MCE_KILL_GET ,
> .BR PR_CAP_AMBIENT + PR_CAP_AMBIENT_IS_SET ,
> +.BR PR_GET_IO_FLUSHER ,
> and (if it returns)
> .BR PR_GET_SECCOMP
> return the nonnegative values described above.
>
--
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] 10+ messages in thread* Re: [PATCH] prctl.2: doc PR_SET/GET_IO_FLUSHER - V4
2020-04-02 12:16 ` Michael Kerrisk (man-pages)
@ 2020-04-04 21:07 ` Mike Christie
2020-04-06 11:00 ` Michael Kerrisk (man-pages)
0 siblings, 1 reply; 10+ messages in thread
From: Mike Christie @ 2020-04-04 21:07 UTC (permalink / raw)
To: Michael Kerrisk (man-pages),
linux-api, david, mhocko, masato.suzuki, damien.lemoal,
darrick.wong, bvanassche, linux-man
On 04/02/2020 07:16 AM, Michael Kerrisk (man-pages) wrote:
> Hello Mike,
>
> On 4/2/20 4:08 AM, Mike Christie wrote:
>> This patch documents the PR_SET_IO_FLUSHER and PR_GET_IO_FLUSHER
>> prctl commands added to the linux kernel for 5.6 in commit:
>>
>> commit 8d19f1c8e1937baf74e1962aae9f90fa3aeab463
>> Author: Mike Christie <mchristi@redhat.com>
>> Date: Mon Nov 11 18:19:00 2019 -0600>
>> prctl: PR_{G,S}ET_IO_FLUSHER to support controlling memory reclaim
>>
>> Signed-off-by: Mike Christie <mchristi@redhat.com>
>
> I've applied this patch, but I have some questions:
Hey,
Thanks for fixing up the patch for me.
>
> (a) What happens to the IO_FLUSHER setting in the child of fork(2)?
The child will inherit the setting.
> (b) What happens to the IO_FLUSHER setting during an execve(2)?
> (Is it preserved, reset, something else?)
It's preserved.
^ permalink raw reply [flat|nested] 10+ messages in thread* Re: [PATCH] prctl.2: doc PR_SET/GET_IO_FLUSHER - V4
2020-04-04 21:07 ` Mike Christie
@ 2020-04-06 11:00 ` Michael Kerrisk (man-pages)
0 siblings, 0 replies; 10+ messages in thread
From: Michael Kerrisk (man-pages) @ 2020-04-06 11:00 UTC (permalink / raw)
To: Mike Christie
Cc: Linux API, Dave Chinner, Michal Hocko, masato.suzuki,
damien.lemoal, Darrick J. Wong, Bart Van Assche, linux-man
Hi Mike,
On Sat, 4 Apr 2020 at 23:07, Mike Christie <mchristi@redhat.com> wrote:
>
> On 04/02/2020 07:16 AM, Michael Kerrisk (man-pages) wrote:
> > Hello Mike,
> >
> > On 4/2/20 4:08 AM, Mike Christie wrote:
> >> This patch documents the PR_SET_IO_FLUSHER and PR_GET_IO_FLUSHER
> >> prctl commands added to the linux kernel for 5.6 in commit:
> >>
> >> commit 8d19f1c8e1937baf74e1962aae9f90fa3aeab463
> >> Author: Mike Christie <mchristi@redhat.com>
> >> Date: Mon Nov 11 18:19:00 2019 -0600>
> >> prctl: PR_{G,S}ET_IO_FLUSHER to support controlling memory reclaim
> >>
> >> Signed-off-by: Mike Christie <mchristi@redhat.com>
> >
> > I've applied this patch, but I have some questions:
>
> Hey,
>
> Thanks for fixing up the patch for me.
you're welcome.
> > (a) What happens to the IO_FLUSHER setting in the child of fork(2)?
>
> The child will inherit the setting.
>
> > (b) What happens to the IO_FLUSHER setting during an execve(2)?
> > (Is it preserved, reset, something else?)
>
> It's preserved.
Thanks. I added this text:
The IO_FLUSHER state is inherited by a child process cre‐
ated via fork(2) and is preserved across execve(2).
Cheers,
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] 10+ messages in thread
end of thread, other threads:[~2020-04-06 11:01 UTC | newest]
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2020-04-02 2:08 [PATCH] prctl.2: doc PR_SET/GET_IO_FLUSHER - V4 Mike Christie
2020-04-02 3:46 ` Bart Van Assche
2020-04-02 12:16 ` Michael Kerrisk (man-pages)
2020-04-02 14:01 ` Michael Christie
2020-04-02 20:12 ` Michael Kerrisk (man-pages)
2020-04-02 6:47 ` Michal Hocko
2020-04-02 12:16 ` Michael Kerrisk (man-pages)
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