Messages in this thread | | | Date | Tue, 10 Sep 2019 06:21:07 +0200 | From | "Ahmed S. Darwish" <> | Subject | Re: Linux 5.3-rc8 |
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Hi,
On Sun, Sep 08, 2019 at 01:59:27PM -0700, Linus Torvalds wrote: > So we probably didn't strictly need an rc8 this release, but with LPC > and the KS conference travel this upcoming week it just makes > everything easier. >
The commit b03755ad6f33 (ext4: make __ext4_get_inode_loc plug), [1] which was merged in v5.3-rc1, *always* leads to a blocked boot on my system due to low entropy.
The hardware is not a VM: it's a Thinkpad E480 (i5-8250U CPU), with a standard Arch user-space.
It was discovered through bisecting the problem v5.2 => v5.3-rc1, since v5.2 never had any similar issues. The issue still persists in v5.3-rc8: reverting that commit always fixes the problem.
It seems that batching the directory lookup I/O requests (which are possibly a lot during boot) is minimizing sources of disk-activity- induced entropy? [2] [3]
Can this even be considered a user-space breakage? I'm honestly not sure. On my modern RDRAND-capable x86, just running rng-tools rngd(8) early-on fixes the problem. I'm not sure about the status of older CPUs though.
Thanks,
[1] commit b03755ad6f33b7b8cd7312a3596a2dbf496de6e7 Author: zhangjs <zachary@baishancloud.com> Date: Wed Jun 19 23:41:29 2019 -0400
ext4: make __ext4_get_inode_loc plug
Add a blk_plug to prevent the inode table readahead from being submitted as small I/O requests.
Signed-off-by: zhangjs <zachary@baishancloud.com> Signed-off-by: Theodore Ts'o <tytso@mit.edu> Reviewed-by: Jan Kara <jack@suse.cz>
[2] https://lkml.kernel.org/r/20190619122457.GF27954@quack2.suse.cz
[3] block/blk-core.c :: blk_start_plug()
-- darwi http://darwish.chasingpointers.com
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