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Date:   Mon, 29 May 2023 14:44:41 +0200
From:   Johan Hovold <johan@kernel.org>
To:     Linus Torvalds <torvalds@linux-foundation.org>
Cc:     Luis Chamberlain <mcgrof@kernel.org>,
        Lucas De Marchi <lucas.demarchi@intel.com>,
        Petr Pavlu <petr.pavlu@suse.com>, gregkh@linuxfoundation.org,
        rafael@kernel.org, song@kernel.org, lucas.de.marchi@gmail.com,
        christophe.leroy@csgroup.eu, peterz@infradead.org, rppt@kernel.org,
        dave@stgolabs.net, willy@infradead.org, vbabka@suse.cz,
        mhocko@suse.com, dave.hansen@linux.intel.com,
        colin.i.king@gmail.com, jim.cromie@gmail.com,
        catalin.marinas@arm.com, jbaron@akamai.com,
        rick.p.edgecombe@intel.com, yujie.liu@intel.com, david@redhat.com,
        tglx@linutronix.de, hch@lst.de, patches@lists.linux.dev,
        linux-modules@vger.kernel.org, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, pmladek@suse.com, prarit@redhat.com,
        lennart@poettering.net
Subject: Re: [PATCH 2/2] module: add support to avoid duplicates early on load
Message-ID: <ZHSeOUpKtyc8VKx5@hovoldconsulting.com>
References: <20230524213620.3509138-1-mcgrof@kernel.org>
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 <8fc5b26b-d2f6-0c8f-34a1-af085dbef155@suse.com>
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 <CAHk-=whu8Wh4JP1hrc80ZvGgVW4GV6hw1vwzSiwOo9-1=Y1dWw@mail.gmail.com>
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On Mon, May 29, 2023 at 07:00:05AM -0400, Linus Torvalds wrote:

> However, can I ask you to just verify that it was purely the exclusive
> open part, and it wasn't that I messed up something else. IOW, can you
> replace the
> 
>         return exclusive_deny_write_access(file);
> 
> in prepare_file_for_module_load() with just a "return 0", and remove the
> 
>                 allow_write_access(f.file);
> 
> line in finit_module()?
> 
> That's obviously _instead_ of the revert that I already pushed out,
> just to verify that "yup, it's that part, not something silly
> elsewhere"

Yes, those two changes are enough to make the problem go away.

> I do wonder what it is that is different in your setup, and maybe you
> could also enable the
> 
>         pr_debug("finit_module: fd=%d, uargs=%p, flags=%i\n", fd, uargs, flags);

Below is the corresponding output with a working kernel: 174 requests
for the 131 modules that end up being loaded (without the revert there
is only around 110 modules loaded).

There is some probe deferral and async probing going on during normal
boot which may be part of the explanation.

Johan

[    0.669112] finit_module: fd=3, uargs=00000000b461506c, flags=0
[    0.674144] finit_module: fd=4, uargs=00000000b461506c, flags=0
[    0.676783] finit_module: fd=5, uargs=00000000b461506c, flags=0
[    0.678920] finit_module: fd=3, uargs=00000000b461506c, flags=0
[    0.837967] finit_module: fd=5, uargs=0000000000157d9f, flags=0
[    0.839414] finit_module: fd=3, uargs=00000000b461506c, flags=0
[    0.844129] finit_module: fd=4, uargs=00000000b461506c, flags=0
[    0.845016] finit_module: fd=3, uargs=00000000b461506c, flags=0
[    0.849132] finit_module: fd=3, uargs=00000000b461506c, flags=0
[    0.849460] finit_module: fd=4, uargs=00000000b461506c, flags=0
[    3.345004] finit_module: fd=4, uargs=00000000e3e6c6d2, flags=0
[    3.364302] finit_module: fd=4, uargs=0000000095136ea7, flags=0
[    3.371928] finit_module: fd=5, uargs=0000000095136ea7, flags=0
[    4.099183] finit_module: fd=3, uargs=00000000ce2d6f3e, flags=0
[    4.103156] finit_module: fd=3, uargs=000000004e3e14c2, flags=0
[    4.713558] finit_module: fd=6, uargs=00000000262da138, flags=0
[    4.715608] finit_module: fd=6, uargs=00000000262da138, flags=0
[    4.717620] finit_module: fd=6, uargs=00000000262da138, flags=0
[    4.717910] finit_module: fd=6, uargs=00000000262da138, flags=0
[    4.719517] finit_module: fd=6, uargs=00000000262da138, flags=0
[    4.725862] finit_module: fd=6, uargs=00000000262da138, flags=0
[    4.726730] finit_module: fd=13, uargs=00000000262da138, flags=0
[    4.727018] finit_module: fd=14, uargs=00000000262da138, flags=0
[    4.730525] finit_module: fd=6, uargs=00000000262da138, flags=0
[    4.749602] finit_module: fd=15, uargs=00000000262da138, flags=0
[    4.749675] finit_module: fd=15, uargs=00000000262da138, flags=0
[    4.749678] finit_module: fd=6, uargs=00000000262da138, flags=0
[    4.774117] finit_module: fd=13, uargs=00000000262da138, flags=0
[    4.795307] finit_module: fd=6, uargs=00000000262da138, flags=0
[    4.797327] finit_module: fd=6, uargs=00000000262da138, flags=0
[    4.798405] finit_module: fd=6, uargs=00000000262da138, flags=0
[    4.799140] finit_module: fd=6, uargs=00000000262da138, flags=0
[    4.800850] finit_module: fd=6, uargs=00000000262da138, flags=0
[    4.807306] finit_module: fd=13, uargs=00000000262da138, flags=0
[    4.807313] finit_module: fd=13, uargs=00000000262da138, flags=0
[    4.807321] finit_module: fd=16, uargs=00000000262da138, flags=0
[    4.807394] finit_module: fd=13, uargs=00000000262da138, flags=0
[    4.807463] finit_module: fd=6, uargs=00000000262da138, flags=0
[    4.807525] finit_module: fd=13, uargs=00000000262da138, flags=0
[    4.807530] finit_module: fd=6, uargs=00000000262da138, flags=0
[    4.807590] finit_module: fd=6, uargs=00000000262da138, flags=0
[    4.811469] finit_module: fd=0, uargs=0000000080fab15b, flags=0
[    4.845851] finit_module: fd=15, uargs=00000000262da138, flags=0
[    4.845875] finit_module: fd=13, uargs=00000000262da138, flags=0
[    4.846282] finit_module: fd=6, uargs=00000000262da138, flags=0
[    4.846363] finit_module: fd=6, uargs=00000000262da138, flags=0
[    4.846363] finit_module: fd=6, uargs=00000000262da138, flags=0
[    4.846669] finit_module: fd=13, uargs=00000000262da138, flags=0
[    4.846994] finit_module: fd=13, uargs=00000000262da138, flags=0
[    4.847005] finit_module: fd=13, uargs=00000000262da138, flags=0
[    4.847194] finit_module: fd=6, uargs=00000000262da138, flags=0
[    4.847356] finit_module: fd=15, uargs=00000000262da138, flags=0
[    4.847448] finit_module: fd=17, uargs=00000000262da138, flags=0
[    4.847556] finit_module: fd=6, uargs=00000000262da138, flags=0
[    4.847651] finit_module: fd=6, uargs=00000000262da138, flags=0
[    4.848175] finit_module: fd=6, uargs=00000000262da138, flags=0
[    4.850005] finit_module: fd=15, uargs=00000000262da138, flags=0
[    4.850485] finit_module: fd=6, uargs=00000000262da138, flags=0
[    4.866031] finit_module: fd=15, uargs=00000000262da138, flags=0
[    4.866032] finit_module: fd=16, uargs=00000000262da138, flags=0
[    4.866381] finit_module: fd=6, uargs=00000000262da138, flags=0
[    4.866711] finit_module: fd=6, uargs=00000000262da138, flags=0
[    4.867757] finit_module: fd=13, uargs=00000000262da138, flags=0
[    4.868360] finit_module: fd=6, uargs=00000000262da138, flags=0
[    4.886043] finit_module: fd=16, uargs=00000000262da138, flags=0
[    4.886046] finit_module: fd=6, uargs=00000000262da138, flags=0
[    4.886046] finit_module: fd=6, uargs=00000000262da138, flags=0
[    4.886060] finit_module: fd=17, uargs=00000000262da138, flags=0
[    4.886114] finit_module: fd=6, uargs=00000000262da138, flags=0
[    4.886140] finit_module: fd=13, uargs=00000000262da138, flags=0
[    4.886326] finit_module: fd=15, uargs=00000000262da138, flags=0
[    4.886716] finit_module: fd=6, uargs=00000000262da138, flags=0
[    4.887210] finit_module: fd=16, uargs=00000000262da138, flags=0
[    4.887451] finit_module: fd=13, uargs=00000000262da138, flags=0
[    4.887811] finit_module: fd=13, uargs=00000000262da138, flags=0
[    4.887963] finit_module: fd=15, uargs=00000000262da138, flags=0
[    4.892066] finit_module: fd=6, uargs=00000000262da138, flags=0
[    4.896048] finit_module: fd=13, uargs=00000000262da138, flags=0
[    4.896070] finit_module: fd=13, uargs=00000000262da138, flags=0
[    4.896092] finit_module: fd=15, uargs=00000000262da138, flags=0
[    4.896157] finit_module: fd=18, uargs=00000000262da138, flags=0
[    4.896193] finit_module: fd=6, uargs=00000000262da138, flags=0
[    4.896211] finit_module: fd=18, uargs=00000000262da138, flags=0
[    4.896737] finit_module: fd=6, uargs=00000000262da138, flags=0
[    4.896751] finit_module: fd=15, uargs=00000000262da138, flags=0
[    4.897174] finit_module: fd=15, uargs=00000000262da138, flags=0
[    4.897343] finit_module: fd=6, uargs=00000000262da138, flags=0
[    4.897388] finit_module: fd=19, uargs=00000000262da138, flags=0
[    4.897555] finit_module: fd=6, uargs=00000000262da138, flags=0
[    4.897592] finit_module: fd=6, uargs=00000000262da138, flags=0
[    4.899657] finit_module: fd=16, uargs=00000000262da138, flags=0
[    4.899973] finit_module: fd=6, uargs=00000000262da138, flags=0
[    4.900316] finit_module: fd=17, uargs=00000000262da138, flags=0
[    4.901188] finit_module: fd=13, uargs=00000000262da138, flags=0
[    4.901668] finit_module: fd=13, uargs=00000000262da138, flags=0
[    4.901708] finit_module: fd=13, uargs=00000000262da138, flags=0
[    4.902030] finit_module: fd=15, uargs=00000000262da138, flags=0
[    4.903964] finit_module: fd=14, uargs=00000000262da138, flags=0
[    4.905243] finit_module: fd=13, uargs=00000000262da138, flags=0
[    4.907083] finit_module: fd=17, uargs=00000000262da138, flags=0
[    4.907480] finit_module: fd=16, uargs=00000000262da138, flags=0
[    4.907519] finit_module: fd=16, uargs=00000000262da138, flags=0
[    4.909481] finit_module: fd=13, uargs=00000000262da138, flags=0
[    4.911705] finit_module: fd=15, uargs=00000000262da138, flags=0
[    4.912056] finit_module: fd=18, uargs=00000000262da138, flags=0
[    4.912079] finit_module: fd=15, uargs=00000000262da138, flags=0
[    4.915340] finit_module: fd=19, uargs=00000000262da138, flags=0
[    4.933199] finit_module: fd=16, uargs=00000000262da138, flags=0
[    4.933585] finit_module: fd=18, uargs=00000000262da138, flags=0
[    4.935169] finit_module: fd=20, uargs=00000000262da138, flags=0
[    4.956021] finit_module: fd=19, uargs=00000000262da138, flags=0
[    4.956797] finit_module: fd=16, uargs=00000000262da138, flags=0
[    4.959865] finit_module: fd=17, uargs=00000000262da138, flags=0
[    4.964171] finit_module: fd=17, uargs=00000000262da138, flags=0
[    4.977073] finit_module: fd=18, uargs=00000000262da138, flags=0
[    4.980167] finit_module: fd=18, uargs=00000000262da138, flags=0
[    5.043379] finit_module: fd=6, uargs=00000000262da138, flags=0
[    5.053709] finit_module: fd=6, uargs=00000000262da138, flags=0
[    5.131232] finit_module: fd=15, uargs=00000000262da138, flags=0
[    5.140785] finit_module: fd=19, uargs=00000000262da138, flags=0
[    5.186244] finit_module: fd=18, uargs=00000000262da138, flags=0
[    5.186247] finit_module: fd=6, uargs=00000000262da138, flags=0
[    5.186252] finit_module: fd=6, uargs=00000000262da138, flags=0
[    5.186451] finit_module: fd=15, uargs=00000000262da138, flags=0
[    5.186507] finit_module: fd=13, uargs=00000000262da138, flags=0
[    5.187345] finit_module: fd=6, uargs=00000000262da138, flags=0
[    5.190282] finit_module: fd=15, uargs=00000000262da138, flags=0
[    5.195744] finit_module: fd=13, uargs=00000000262da138, flags=0
[    5.198242] finit_module: fd=16, uargs=00000000262da138, flags=0
[    5.198271] finit_module: fd=20, uargs=00000000262da138, flags=0
[    5.222394] finit_module: fd=6, uargs=00000000262da138, flags=0
[    5.222395] finit_module: fd=6, uargs=00000000262da138, flags=0
[    5.222407] finit_module: fd=16, uargs=00000000262da138, flags=0
[    5.222430] finit_module: fd=21, uargs=00000000262da138, flags=0
[    5.222432] finit_module: fd=16, uargs=00000000262da138, flags=0
[    5.222443] finit_module: fd=15, uargs=00000000262da138, flags=0
[    5.229650] finit_module: fd=22, uargs=00000000262da138, flags=0
[    5.257981] finit_module: fd=6, uargs=00000000262da138, flags=0
[    5.313560] finit_module: fd=6, uargs=00000000262da138, flags=0
[    6.144316] finit_module: fd=6, uargs=00000000262da138, flags=0
[    6.178956] finit_module: fd=6, uargs=00000000262da138, flags=0
[    6.178961] finit_module: fd=6, uargs=00000000262da138, flags=0
[    6.182057] finit_module: fd=13, uargs=00000000262da138, flags=0
[    6.182067] finit_module: fd=13, uargs=00000000262da138, flags=0
[    6.243708] finit_module: fd=0, uargs=00000000f9e4f67e, flags=0
[    6.249397] finit_module: fd=0, uargs=000000001b26db10, flags=0
[    6.249904] finit_module: fd=1, uargs=000000001b26db10, flags=0
[    6.250626] finit_module: fd=2, uargs=000000001b26db10, flags=0
[    6.251515] finit_module: fd=3, uargs=000000001b26db10, flags=0
[    6.254112] finit_module: fd=4, uargs=000000001b26db10, flags=0
[    6.255129] finit_module: fd=6, uargs=00000000262da138, flags=0
[    6.255504] finit_module: fd=6, uargs=00000000262da138, flags=0
[    6.259256] finit_module: fd=0, uargs=00000000e1b6cfe4, flags=0
[    6.264136] finit_module: fd=0, uargs=000000004070418f, flags=0
[    6.265227] finit_module: fd=1, uargs=000000004070418f, flags=0
[    6.270175] finit_module: fd=0, uargs=0000000092757077, flags=0
[    6.271230] finit_module: fd=1, uargs=0000000092757077, flags=0
[    6.322960] finit_module: fd=3, uargs=00000000fb904223, flags=0
[    6.373125] finit_module: fd=0, uargs=00000000e2cdc73f, flags=0
[    6.380061] finit_module: fd=0, uargs=000000000591e4e9, flags=0
[    6.392296] finit_module: fd=0, uargs=0000000088d2796a, flags=0
[    6.464595] finit_module: fd=0, uargs=000000001aa8b42e, flags=0
[    6.479839] finit_module: fd=0, uargs=00000000de50a030, flags=0
[    6.488790] finit_module: fd=0, uargs=00000000cbcb6a65, flags=0
[    6.492573] finit_module: fd=1, uargs=00000000cbcb6a65, flags=0
[    6.514903] finit_module: fd=0, uargs=000000006f393376, flags=0
[    7.989970] finit_module: fd=0, uargs=00000000c4594f52, flags=0
[   11.492886] finit_module: fd=13, uargs=00000000262da138, flags=0
[   11.639532] finit_module: fd=6, uargs=00000000262da138, flags=0
[   11.640048] finit_module: fd=6, uargs=00000000262da138, flags=0
[   11.640997] finit_module: fd=15, uargs=00000000262da138, flags=0
[   11.641049] finit_module: fd=6, uargs=00000000262da138, flags=0
[   11.775051] finit_module: fd=6, uargs=00000000262da138, flags=0
[   11.776806] finit_module: fd=6, uargs=00000000262da138, flags=0