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    SubjectRe: Linux 5.3-rc8
    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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