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On recent kernels, zfs_zevent_console=1 outputs many spurious linefeeds #7082

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akorn opened this issue Jan 26, 2018 · 7 comments
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On recent kernels, zfs_zevent_console=1 outputs many spurious linefeeds #7082

akorn opened this issue Jan 26, 2018 · 7 comments
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good first issue Indicates a good issue for first-time contributors Type: Defect Incorrect behavior (e.g. crash, hang)

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@akorn
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akorn commented Jan 26, 2018

This is almost certainly due to the change explained in https://lwn.net/Articles/732420/ -- if you call printk() several times, each invocation will cause a new line to be written to dmesg unless you use KERN_CONT.

Supposedly, you should instead marshal your entire line into a single buffer and use printk() to print that.
@akorn
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akorn commented Jan 26, 2018

(Incidentally, I also think zfs_zevent_cols is superfluous -- whatever you view the messages on can wrap them. I don't think there is need for pre-wrapping in kernelspace. I don't think this merits filing a new issue, but if fixing the printk usage is easier if you also drop zfs_zevent_cols, I think it'd be good riddance.)

@DeHackEd
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From IRC: https://pastebin.com/SbtYRcs1 for an example of broken output

@behlendorf
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@akorn thanks for letting us know. I'm actually a little surprised anyone is enabling the console logging functionality and would be interested in how your using it. This is functionality we've considering removing entirely.

@WoefulDerelict WoefulDerelict mentioned this issue Jan 26, 2018
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@akorn
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akorn commented Jan 27, 2018

I have a system not unlike logcheck that post-processes logfiles, and, based on regular expressions, discards all messages classified as "known benign". It sends me the others via email for review.

I'm sure it would be possible to set this up with zed somehow, but I had already been using it when zed was introduced (or when I first noticed zed, at any rate).

While it wouldn't be a terrible blow to lose zfs_zevent_console, I think it's useful to see these messages interleaved with other kernel events, in the same stream. Makes it easier to spot if other problems coincide with zfs events.

@akorn akorn changed the title On recent kernels, zfs_zevent_cols=1 outputs many spurious linefeeds On recent kernels, zfs_zevent_console=1 outputs many spurious linefeeds Jan 27, 2018
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stale bot commented Aug 25, 2020

This issue has been automatically marked as "stale" because it has not had any activity for a while. It will be closed in 90 days if no further activity occurs. Thank you for your contributions.

@stale stale bot added the Status: Stale No recent activity for issue label Aug 25, 2020
@akorn
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akorn commented Aug 25, 2020

AFAIK the problem still persists, but since it made zfs_zevent_console pretty much useless I have stopped using it.

I think that knob should either go away as you, @behlendorf, suggested, or the output should be fixed.

@stale stale bot removed the Status: Stale No recent activity for issue label Aug 25, 2020
@behlendorf behlendorf added good first issue Indicates a good issue for first-time contributors Type: Defect Incorrect behavior (e.g. crash, hang) labels Aug 25, 2020
@behlendorf
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I'd recommend we remove it.

nabijaczleweli added a commit to nabijaczleweli/zfs that referenced this issue May 4, 2021
@nabijaczleweli
module/zfs: remove zfs_zevent_console and zfs_zevent_cols
8d4a26e 
zfs_zevent_console committed multiple printk()s per line without
properly continuing them ‒ a single event could easily be fragmented
across over thirty lines, making it useless for direct application

zfs_zevent_cols exists purely to wrap the output from zfs_zevent_console

The niche this was supposed to fill can be better served by something
akin to the all-syslog ZEDLET

Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>
Closes openzfs#7082
@nabijaczleweli nabijaczleweli mentioned this issue May 4, 2021
Merged
13 tasks
nabijaczleweli added a commit to nabijaczleweli/zfs that referenced this issue May 8, 2021
@nabijaczleweli
module/zfs: remove zfs_zevent_console and zfs_zevent_cols
e81e4da 
zfs_zevent_console committed multiple printk()s per line without
properly continuing them ‒ a single event could easily be fragmented
across over thirty lines, making it useless for direct application

zfs_zevent_cols exists purely to wrap the output from zfs_zevent_console

The niche this was supposed to fill can be better served by something
akin to the all-syslog ZEDLET

Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>
Closes openzfs#7082
nabijaczleweli added a commit to nabijaczleweli/zfs that referenced this issue May 8, 2021
@nabijaczleweli
module/zfs: remove zfs_zevent_console and zfs_zevent_cols
19576dd 
zfs_zevent_console committed multiple printk()s per line without
properly continuing them ‒ a single event could easily be fragmented
across over thirty lines, making it useless for direct application

zfs_zevent_cols exists purely to wrap the output from zfs_zevent_console

The niche this was supposed to fill can be better served by something
akin to the all-syslog ZEDLET

Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>
Closes openzfs#7082
behlendorf pushed a commit to behlendorf/zfs that referenced this issue May 28, 2021
@nabijaczleweli @behlendorf
module/zfs: remove zfs_zevent_console and zfs_zevent_cols
1cb517a 
zfs_zevent_console committed multiple printk()s per line without
properly continuing them ‒ a single event could easily be fragmented
across over thirty lines, making it useless for direct application

zfs_zevent_cols exists purely to wrap the output from zfs_zevent_console

The niche this was supposed to fill can be better served by something
akin to the all-syslog ZEDLET

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>
Closes openzfs#7082 
Closes openzfs#11996
sempervictus pushed a commit to sempervictus/zfs that referenced this issue May 31, 2021
@nabijaczleweli
module/zfs: remove zfs_zevent_console and zfs_zevent_cols
d974a0b 
zfs_zevent_console committed multiple printk()s per line without
properly continuing them ‒ a single event could easily be fragmented
across over thirty lines, making it useless for direct application

zfs_zevent_cols exists purely to wrap the output from zfs_zevent_console

The niche this was supposed to fill can be better served by something
akin to the all-syslog ZEDLET

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>
Closes openzfs#7082 
Closes openzfs#11996
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