linux-ext4 - Re: [bugzilla:219548] the kernel crashes when storing an EXT4 file system in a ZRAM device

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Message-ID: <20241212141220.GE1265540@mit.edu>
Date: Thu, 12 Dec 2024 09:12:20 -0500
From: "Theodore Ts'o" <tytso@....edu>
To: Christoph Hellwig <hch@...radead.org>
Cc: Sergey Senozhatsky <senozhatsky@...omium.org>,
        Jens Axboe <axboe@...nel.dk>, caiqingfu <baicaiaichibaicai@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>, linux-ext4@...r.kernel.org,
        linux-block@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: [bugzilla:219548] the kernel crashes when storing an EXT4 file
 system in a ZRAM device

On Thu, Dec 12, 2024 at 09:04:37AM -0500, Theodore Ts'o wrote:
> For this particular use case, which is running VM's on
> Chromium/ChromeOS, I suspect we do need to have some kind of solution
> other than triggering a WARN_ON.

Sorry, I didn't complete my thought here.  We could just say, "don't
use ext4 without a journal in a Chrome VM."  But if the are going to
allow the VM's access to external USB storage, then ext4 in no-journal
mode will be the least of their problems.  People trying to access USB
thumbdrives or sdcards from their digital cameras using FAT file
sytems will be trigerring ZBLK buffer overflow kernel crashes left,
right, and center.  Especially if they are on a low-cost ChromeOS
device with a tiny amount of meory, such that memory pressure should
be considered a foregone conclusion.  :-)

						- Ted