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SubjectRe: [PATCH] mm/page_alloc: Correct return value of populated elements if bulk array is populated
Hi Mel,

On Mon, Jun 28, 2021 at 5:29 PM Mel Gorman <mgorman@techsingularity.net> wrote:
> Dave Jones reported the following
>
> This made it into 5.13 final, and completely breaks NFSD for me
> (Serving tcp v3 mounts). Existing mounts on clients hang, as do
> new mounts from new clients. Rebooting the server back to rc7
> everything recovers.
>
> The commit b3b64ebd3822 ("mm/page_alloc: do bulk array bounds check after
> checking populated elements") returns the wrong value if the array is
> already populated which is interpreted as an allocation failure. Dave
> reported this fixes his problem and it also passed a test running dbench
> over NFS.
>
> Fixes: b3b64ebd3822 ("mm/page_alloc: do bulk array bounds check after checking populated elements")
> Reported-and-tested-by: Dave Jones <davej@codemonkey.org.uk>
> Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
> Cc: <stable@vger.kernel.org> [5.13+]

I saw similar failures as Mike Galbraith when doing s2idle or s2ram
on some boards with some configs:

Freezing of tasks failed after 20.004 seconds (1 tasks refusing to
freeze, wq_busy=0):
task:NFSv4 callback state:S stack: 0 pid: 280 ppid: 2
flags:0x00000000
[<c094b634>] (__schedule) from [<c094b8d0>] (schedule+0xc0/0x110)
[<c094b8d0>] (schedule) from [<c094faec>] (schedule_timeout+0xc8/0x108)
[<c094faec>] (schedule_timeout) from [<c092e0a0>] (svc_recv+0x108/0xa30)
[<c092e0a0>] (svc_recv) from [<c04c5990>] (nfs4_callback_svc+0x6c/0x84)
[<c04c5990>] (nfs4_callback_svc) from [<c0244ddc>] (kthread+0x128/0x138)
[<c0244ddc>] (kthread) from [<c0200114>] (ret_from_fork+0x14/0x20)

I've bisected it (twice, as I couldn't believe the result) to the
same commit, which helped me find the fix.

After cherry-picking commit 66d9282523b32281 ("mm/page_alloc: Correct
return value of populated elements if bulk array is populated"),
the problem went away.

Tested-by: Geert Uytterhoeven <geert+renesas@glider.be>

Gr{oetje,eeting}s,

Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds

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