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Date:   Thu, 19 Mar 2020 17:36:13 +0100
From:   Jan Kara <jack@suse.cz>
To:     "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>
Cc:     linux-ext4@vger.kernel.org, "Theodore Y. Ts'o" <tytso@mit.edu>,
        Ritesh Harjani <riteshh@linux.ibm.com>
Subject: Re: Ext4 corruption with VM images as 3 > drop_caches
Message-ID: <20200319163613.GA3339@quack2.suse.cz>
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Hi!

On Wed 18-03-20 09:17:51, Aneesh Kumar K.V wrote:
> With new vm install I am finding corruption with the vm image if I
> follow up the install with echo 3 > /proc/sys/vm/drop_caches 
> 
> The file system reports below error.
> 
> Begin: Running /scripts/local-bottom ... done.
> Begin: Running /scripts/init-bottom ...
> [    4.916017] EXT4-fs error (device vda2): ext4_lookup:1700: inode #787185: comm sh: iget: checksum invalid
> done.
> [    5.244312] EXT4-fs error (device vda2): ext4_lookup:1700: inode #917954: comm init: iget: checksum invalid
> [    5.257246] EXT4-fs error (device vda2): ext4_lookup:1700: inode #917954: comm init: iget: checksum invalid
> /sbin/init: error while loading shared libraries: libc.so.6: cannot open shared object file: Error 74
> [    5.271207] Kernel panic - not syncing: Attempted to kill init! exitcode=0x00007f00
> 
> And debugfs reports
> 
> debugfs:  stat <917954>
> Inode: 917954   Type: bad type    Mode:  0000   Flags: 0x0
> Generation: 0    Version: 0x00000000
> User:     0   Group:     0   Size: 0
> File ACL: 0
> Links: 0   Blockcount: 0
> Fragment:  Address: 0    Number: 0    Size: 0
> ctime: 0x00000000 -- Wed Dec 31 18:00:00 1969
> atime: 0x00000000 -- Wed Dec 31 18:00:00 1969
> mtime: 0x00000000 -- Wed Dec 31 18:00:00 1969
> Size of extra inode fields: 0
> Inode checksum: 0x00000000
> BLOCKS:
> debugfs:  
> 
> Bisecting this finds 
> Commit 244adf6426ee31a83f397b700d964cff12a247d3("ext4: make
> dioread_nolock the default") as bad. If I revert the same on top of linus
> upstream(fb33c6510d5595144d585aa194d377cf74d31911) I don't hit the
> corrupttion anymore.

Thanks for report and the bisection! Is this guest or host kernel that you
were bisecting? I presume host but I want to make sure.

								Honza
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR