linux-ext4 - sync causing a flush with no data

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Date: Fri, 02 Feb 2024 15:40:47 -0500
From: Phillip Susi <phill@...susis.net>
To: linux-ext4@...r.kernel.org
Subject: sync causing a flush with no data

I have noticed that when entering suspend-to-ram, the kernel syncs the
filesystem, and ext4 issues a flush even though nothing has been
written, causing a disk that has been suspended with runtime pm to wake
up for no reason.

It looks like ext4_sync_fs() calls jbd2_trans_will_send_data_barrier(),
which returns 0, causing a call to blkdev_issue_flush().  Shouldn't this
return a 1 if the transaction is empty?