linux-ext4 - [Bug 218932] Serious problem with ext4 with all kernels, auto-commits do not settle to block device

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Message-ID: <bug-218932-13602-vcnCYagqhU@https.bugzilla.kernel.org/>
Date: Wed, 05 Jun 2024 20:47:09 +0000
From: bugzilla-daemon@...nel.org
To: linux-ext4@...r.kernel.org
Subject: [Bug 218932] Serious problem with ext4 with all kernels,
 auto-commits do not settle to block device

https://bugzilla.kernel.org/show_bug.cgi?id=218932

--- Comment #5 from Serious (sirius@...lhaven.com) ---
/proc/sys/vm/dirty_expire_centisecs 3000
This contradicts information from
https://www.kernel.org/doc/Documentation/filesystems/ext4.txt
commit=nrsec    (*)     Ext4 can be told to sync all its data and metadata
                        every 'nrsec' seconds. The default value is 5 seconds.
                        This means that if you lose your power, you will lose
                        as much as the latest 5 seconds of work (your
                        filesystem will not be damaged though, thanks to the
                        journaling).  This default value (or any low value)
                        will hurt performance, but it's good for data-safety.
                        Setting it to 0 will have the same effect as leaving
                        it at the default (5 seconds).
                        Setting it to very large values will improve
                        performance.

So actually commit=5 does NOT guarantee, that if you lose your power, you will
lose as much as the latest 5 seconds of work. You will lose 30 seconds of work.

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