Bug#909473: fstrim shows incorrect trimmed size after reboot

From	Laurent Bigonville <bigon@debian.org>
Newsgroups	linux.debian.bugs.dist, linux.debian.kernel
Subject	Bug#909473: fstrim shows incorrect trimmed size after reboot
Date	2021-06-08 23:50 +0200
Message-ID	<CnRLH-6j9-1@gated-at.bofh.it> (permalink)
References	(2 earlier) <wBxnA-5dG-1@gated-at.bofh.it> <CnKqS-1Sy-5@gated-at.bofh.it> <CnPTB-5aE-29@gated-at.bofh.it> <wBxnA-5dG-1@gated-at.bofh.it> <CnPTB-5aE-29@gated-at.bofh.it>
Organization	linux.* mail to news gateway

Cross-posted to 2 groups.

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Le 8/06/21 à 21:24, Bastian Blank a écrit :
> Hi
Hello,
> On Tue, Jun 08, 2021 at 03:48:11PM +0200, Laurent Bigonville wrote:
>>>> There is definitely something boggus here
>> Yes, just tested it now and  it's still happening with the kernel currently
>> in unstable (5.10.40-1)
> Why do you think this numbers are wrong?  "fstrim" initially requests
> discard of all unused blocks, so a large number.  But why should it do
> the same on subsequent calls while it still knows what it did the last
> time?
>
> ext4 caches the information if a particular block group was trimmed, but
> this information is not persistent.  (Using bit
> EXT4_GROUP_INFO_WAS_TRIMMED_BIT in ext4_group_info.bb_state.)

Well I would expect that if I'm running fstrim, the same blocks would 
not be trimmed again (even after reboot) if I'm running the command again

Here it seems that it's the case, the number of blocks that are being 
trimmed are the same after reboot.

Are the discard commands delayed and actually not executed when the 
command is run, or am I overlooking something?

Thread

Bug#909473: fstrim shows incorrect trimmed size after reboot Salvatore Bonaccorso <carnil@debian.org> - 2021-05-28 21:40 +0200
  Processed: Re: Bug#909473: fstrim shows incorrect trimmed size  after reboot "Debian Bug Tracking System" <owner@bugs.debian.org> - 2021-05-28 21:40 +0200
  Bug#909473: fstrim shows incorrect trimmed size after reboot Laurent Bigonville <bigon@debian.org> - 2021-06-08 16:00 +0200
    Processed: Re: Bug#909473: fstrim shows incorrect trimmed size  after reboot "Debian Bug Tracking System" <owner@bugs.debian.org> - 2021-06-08 16:00 +0200
    Bug#909473: fstrim shows incorrect trimmed size after reboot Bastian Blank <waldi@debian.org> - 2021-06-08 21:50 +0200
      Bug#909473: fstrim shows incorrect trimmed size after reboot Laurent Bigonville <bigon@debian.org> - 2021-06-08 23:50 +0200
        Bug#909473: fstrim shows incorrect trimmed size after reboot Bastian Blank <waldi@debian.org> - 2021-06-09 00:00 +0200

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