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Date:   Thu, 27 Apr 2023 18:26:11 -0700
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Subject: Re: [PATCH v2] dax: enable dax fault handler to report
 VM_FAULT_HWPOISON
Content-Language: en-US
To:     Matthew Wilcox <willy@infradead.org>
Cc:     Dan Williams <dan.j.williams@intel.com>, vishal.l.verma@intel.com,
        dave.jiang@intel.com, ira.weiny@intel.com, viro@zeniv.linux.org.uk,
        brauner@kernel.org, nvdimm@lists.linux.dev,
        linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org
References: <20230406230127.716716-1-jane.chu@oracle.com>
 <644aeadcba13b_2028294c9@dwillia2-xfh.jf.intel.com.notmuch>
 <a3c1bef3-4226-7c24-905a-d58bd67b89f1@oracle.com>
 <ZEsJxwbIeq3jHDBT@casper.infradead.org>
From:   Jane Chu <jane.chu@oracle.com>
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On 4/27/2023 4:48 PM, Matthew Wilcox wrote:
> On Thu, Apr 27, 2023 at 04:36:58PM -0700, Jane Chu wrote:
>>> This change results in EHWPOISON leaking to usersapce in the case of
>>> read(2), that's not a return code that block I/O applications have ever
>>> had to contend with before. Just as badblocks cause EIO to be returned,
>>> so should poisoned cachelines for pmem.
>>
>> The read(2) man page (https://man.archlinux.org/man/read.2) says
>> "On error, -1 is returned, and errno is set to indicate the error. In this
>> case, it is left unspecified whether the file position (if any) changes."
>>
>> If read(2) users haven't dealt with EHWPOISON before, they may discover that
>> with pmem backed dax file, it's possible.
> 
> I don't think they should.  While syscalls are allowed to return errnos
> other than the ones listed in POSIX, I don't think this is a worthwhile
> difference.  We should be abstracting from the user that this is pmem
> rather than spinning rust or nand.  So we should convert the EHWPOISON
> to EIO as Dan suggests.

Got it, I'll add errno conversion in the respin.

thanks,
-jane