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Date:   Sat, 24 Jun 2023 22:51:42 -0700
From:   Dan Williams <dan.j.williams@intel.com>
To:     Jane Chu <jane.chu@oracle.com>, <dan.j.williams@intel.com>,
        <vishal.l.verma@intel.com>, <dave.jiang@intel.com>,
        <ira.weiny@intel.com>, <willy@infradead.org>,
        <viro@zeniv.linux.org.uk>, <brauner@kernel.org>,
        <nvdimm@lists.linux.dev>, <linux-kernel@vger.kernel.org>,
        <linux-fsdevel@vger.kernel.org>
Subject: RE: [PATCH v5 1/1] dax: enable dax fault handler to report
 VM_FAULT_HWPOISON
Message-ID: <6497d5ee65a8f_2ed729471@dwillia2-xfh.jf.intel.com.notmuch>
References: <20230615181325.1327259-1-jane.chu@oracle.com>
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Jane Chu wrote:
> When multiple processes mmap() a dax file, then at some point,
> a process issues a 'load' and consumes a hwpoison, the process
> receives a SIGBUS with si_code = BUS_MCEERR_AR and with si_lsb
> set for the poison scope. Soon after, any other process issues
> a 'load' to the poisoned page (that is unmapped from the kernel
> side by memory_failure), it receives a SIGBUS with
> si_code = BUS_ADRERR and without valid si_lsb.
> 
> This is confusing to user, and is different from page fault due
> to poison in RAM memory, also some helpful information is lost.
> 
> Channel dax backend driver's poison detection to the filesystem
> such that instead of reporting VM_FAULT_SIGBUS, it could report
> VM_FAULT_HWPOISON.
> 
> If user level block IO syscalls fail due to poison, the errno will
> be converted to EIO to maintain block API consistency.
> 
> Signed-off-by: Jane Chu <jane.chu@oracle.com>

Reviewed-by: Dan Williams <dan.j.williams@intel.com>