From: Stephen Warren <swarren@wwwdotorg.org>
To: Christoph Hellwig <hch@infradead.org>
Cc: Jens Axboe <axboe@kernel.dk>,
linux-block@vger.kernel.org, Simon Glass <sjg@chromium.org>
Subject: Re: dd, close(), sync, and the Linux disk cache
Date: Wed, 19 Feb 2020 10:01:42 -0700 [thread overview]
Message-ID: <dfff89c0-d3cf-96a0-7f44-4d2256a3aba3@wwwdotorg.org> (raw)
In-Reply-To: <20200219163258.GB18377@infradead.org>
On 2/19/20 9:32 AM, Christoph Hellwig wrote:
> On Wed, Feb 12, 2020 at 05:02:43PM -0700, Stephen Warren wrote:
>> Jens et. al.,
>>
>> If I dd to an SD card (e.g. via a USB SD card reader), is it required to run
>> sync afterward in order to guarantee that all written data is written to the
>> SD card? I'm running dd with a simple command-line like "dd if=file.img
>> of=/dev/sdc".
>
> Yes. Or use of=dsync on the dd command line.
Can you explain further why it's necessary given that the kernel
explicitly blocks execution of close() to flush buffers to disk,
assuming the process is the last one with the device open? Am I
misinterpreting the code path I mentioned later in my email? In
practice, I can see this happening when I use dd.
next prev parent reply other threads:[~2020-02-19 17:01 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-13 0:02 dd, close(), sync, and the Linux disk cache Stephen Warren
2020-02-19 16:32 ` Christoph Hellwig
2020-02-19 17:01 ` Stephen Warren [this message]
2020-02-19 17:13 ` Alberto Faria
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