linux-ext4 - Re: [PATCH] unix_io.c: fix deadlock problem in unix_write

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Date:   Mon, 30 Jan 2023 22:12:43 -0500
From:   "Theodore Ts'o" <tytso@....edu>
To:     zhanchengbin <zhanchengbin1@...wei.com>
Cc:     linux-ext4@...r.kernel.org, linfeilong <linfeilong@...wei.com>,
        liuzhiqiang26@...wei.com
Subject: Re: [PATCH] unix_io.c: fix deadlock problem in unix_write_blk64

On Wed, Jan 25, 2023 at 01:18:06AM -0500, Theodore Ts'o wrote:
> 
> Fortunately, we're safe on the read side, because we currently very
> carefully do not call raw_read_blk() while holding the CACHE_MUTEX.
> Instead, we write the data from the user-supplied buffer, and *then*
  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> take the cache mutex, and then save the data from the user-supplied
> buffer into the cache.

Correction: the last sentence of this paragraph should begin:

"Instead, we READ the data INTO the user-supplied buffer, ..."

I have a series of patches that should address the deadlock issue,
that I'll be sending out shortly.

						- Ted