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From: Chris Dunlop <>
To: Dave Chinner <>
Cc: Eric Sandeen <>,
Subject: Re: Mysterious ENOSPC
Date: Fri, 17 Sep 2021 16:07:38 +1000	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <20210902014206.GN2566745@dread.disaster.area>

On Thu, Sep 02, 2021 at 11:42:06AM +1000, Dave Chinner wrote:
> On Mon, Aug 30, 2021 at 08:04:57AM +1000, Dave Chinner wrote:
>> FWIW, if you are using reflink heavily and you have rmap enabled (as
>> you have), there's every chance that an AG has completely run out of
>> space and so new rmap records for shared extents can't be allocated
>> - that can give you spurious ENOSPC errors before the filesystem is
>> 100% full, too.
>> i.e. every shared extent in the filesystem has a rmap record
>> pointing back to each owner of the shared extent. That means for an
>> extent shared 1000 times, there are 1000 rmap records for that
>> shared extent. If you share it again, a new rmap record needs to be
>> inserted into the rmapbt, and if the AG is completely out of space
>> this can fail w/ ENOSPC. Hence you can get ENOSPC errors attempting
>> to shared or unshare extents because there isn't space in the AG for
>> the tracking metadata for the new extent record....
> Ok, now I've seen the filesystem layout, I can say that the
> preconditions for per-ag ENOSPC conditions do actually exist. Hence
> we now really need to know what operation is reporting ENOSPC. I
> guess we'll just have to wait for that to occur again and hope your
> scripts capture it.

FYI, "something" seems to have changed without any particular prompting 
and there haven't been any ENOSPC events in the last 3 weeks whereas 
previously they were occurring 4-5 times a week. Sigh.



      reply	other threads:[~2021-09-17  6:07 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-26  2:06 XFS fallocate implementation incorrectly reports ENOSPC Chris Dunlop
2021-08-26 15:05 ` Eric Sandeen
2021-08-26 20:56   ` Chris Dunlop
2021-08-27  2:55     ` Chris Dunlop
2021-08-27  5:49       ` Dave Chinner
2021-08-27  6:53         ` Chris Dunlop
2021-08-27 22:03           ` Dave Chinner
2021-08-28  0:21             ` Mysterious ENOSPC [was: XFS fallocate implementation incorrectly reports ENOSPC] Chris Dunlop
2021-08-28  3:58               ` Chris Dunlop
2021-08-29 22:04                 ` Dave Chinner
2021-08-30  4:21                   ` Darrick J. Wong
2021-08-30  7:40                     ` Chris Dunlop
2021-08-30  7:37                   ` Mysterious ENOSPC Chris Dunlop
2021-09-02  1:42                     ` Dave Chinner
2021-09-17  6:07                       ` Chris Dunlop [this message]

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