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From:   Michael Walle <michael@walle.cc>
To:     liuxp11@chinatelecom.cn
Cc:     linux-kernel@vger.kernel.org, viro@zeniv.linux.org.uk,
        Michael Walle <michael@walle.cc>
Subject: Re: [PATCH] iov_iter: Fix repeated minus operation
Date:   Thu, 14 Jul 2022 13:46:15 +0200
Message-Id: <20220714114615.3346852-1-michael@walle.cc>
In-Reply-To: <1657707820-124858-1-git-send-email-liuxp11@chinatelecom.cn>
References: <1657707820-124858-1-git-send-email-liuxp11@chinatelecom.cn>
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> After executing command 'cat /proc/cpuinfo', got a message:
> 
> [    6.909745] ------------[ cut here ]------------
> [    6.910267] WARNING: CPU: 0 PID: 76 at lib/iov_iter.c:1026
> iov_iter_pipe+0x34/0x40
> [    6.910951] Modules linked in:
> [    6.911584] CPU: 0 PID: 76 Comm: cat Not tainted 5.19.0-rc6-next-20220711 #9
> [    6.911916] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
> rel-1.12.0-59-gc9ba5276e321-prebuilt.qemu.org 04/01/2014
> [    6.912668] RIP: 0010:iov_iter_pipe+0x34/0x40
> [    6.913062] Code: 72 54 39 72 5c 76 23 48 c7 07 00 00 00 00 48 c7 47 08 00 00
> 00 00 c6 07 03 48 89 4f 10 48 89 57 18 89 47 20 89 47 24 c3 0f 0b <0f> 7
> [    6.914341] RSP: 0018:ffffc900001c7d48 EFLAGS: 00000246
> [    6.914647] RAX: 0000000000000010 RBX: ffff888004988700 RCX: 0000000000000000
> [    6.914893] RDX: ffff88800490bc00 RSI: 0000000000000010 RDI: ffffc900001c7d58
> [    6.915302] RBP: ffffc900001c7e00 R08: 0000000000000000 R09: ffff888004cafad8
> [    6.915609] R10: 0000000000020000 R11: 0000000000001000 R12: ffff88800490bc00
> [    6.915856] R13: ffffc900001c7e48 R14: 00000000000002d5 R15: ffff88800490bc00
> [    6.916352] FS:  00000000016df8c0(0000) GS:ffff88800f600000(0000)

Thanks, I'm getting the same warning and also if you do a cat on any sysfs
file.

> Checking the code, need to delete the duplicate minus in a loop.
>
> Signed-off-by: Liu Xinpeng <liuxp11@chinatelecom.cn>

Fixes: 3d246b875f31 ("ITER_PIPE: allocate buffers as we go in copy-to-pipe primitives")
Tested-by: Michael Walle <michael@walle.cc>

-michael