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Date: Thu, 17 Jul 2025 09:03:57 -0700
From: "Darrick J. Wong" <djwong@kernel.org>
To: Wang Yugui <wangyugui@e16-tech.com>
Cc: linux-xfs@vger.kernel.org
Subject: Re: a deadloop(?) when mkfs.xfs -o rtdev
Message-ID: <20250717160357.GQ2672049@frogsfrogsfrogs>
References: <20250717081332.E87F.409509F4@e16-tech.com>
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In-Reply-To: <20250717081332.E87F.409509F4@e16-tech.com>

On Thu, Jul 17, 2025 at 08:13:33AM +0800, Wang Yugui wrote:
> Hi,
> 
> There seems a deadloop(?) when mkfs.xfs -o rtdev.
> 
> # mkfs.xfs -r rtdev=/dev/disk/by-id/ata-MZ7KM1T6HAJM00D3_S2CXNAAH600026 /dev/d
> isk/by-id/scsi-SHITACHI_HUSMH842_CLAR100_0LX0JWVA -f
> meta-data=/dev/disk/by-id/scsi-SHITACHI_HUSMH842_CLAR100_0LX0JWVA isize=512    agcount=20, agsize=1221072 blks
>          =                       sectsz=4096  attr=2, projid32bit=1
>          =                       crc=1        finobt=1, sparse=1, rmapbt=0
>          =                       reflink=0    bigtime=1 inobtcount=1 nrext64=1
>          =                       exchange=0
> data     =                       bsize=4096   blocks=24421440, imaxpct=25
>          =                       sunit=0      swidth=0 blks
> naming   =version 2              bsize=4096   ascii-ci=0, ftype=1, parent=0
> log      =internal log           bsize=4096   blocks=41799, version=2
>          =                       sectsz=4096  sunit=1 blks, lazy-count=1
> realtime =/dev/disk/by-id/ata-MZ7KM1T6HAJM00D3_S2CXNAAH600026 extsz=4096   blocks=390703446, rtextents=390703446
> Discarding blocks...Done.
> Discarding blocks...Done.
> 
> It did not fishish after 10 mins.
> 
> # pstack 5785
> #0  0x00007f8df5efc01a in pread64 () from /lib64/libc.so.6
> #1  0x0000557b7bbfe9c3 in __read_buf.constprop.0 ()
> #2  0x0000557b7bbc3030 in libxfs_buf_read_map ()
> #3  0x0000557b7bbfe1ae in libxfs_trans_read_buf_map.constprop ()
> #4  0x0000557b7bbee7ef in xfs_rtbuf_get ()
> #5  0x0000557b7bbf03d8 in libxfs_rtfree_extent ()
> #6  0x0000557b7bbbb322 in parseproto.lto_priv ()
> #7  0x0000557b7bbb7643 in main ()
> 
> And,
> 1) more chance happen when kernel 6.12.36, but yet not happen when kernel 6.6.93.
> 2) it happen on both xfsprogs-6.11.0 and xfsprogs-6.4.

You /could/ strace the mkfs process to see if it's really stuck, or just
issuing IOs really slowly.

--D

> 
> Best Regards
> Wang Yugui (wangyugui@e16-tech.com)
> 2025/07/17
> 
> 
>