From: Dan Williams <dan.j.williams@intel.com>
To: Logan Gunthorpe <logang@deltatee.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Jens Axboe <axboe@kernel.dk>, Boaz Harrosh <boaz@plexistor.com>,
"linux-nvdimm@lists.01.org" <linux-nvdimm@lists.01.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Linux MM <linux-mm@kvack.org>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
Ross Zwisler <ross.zwisler@linux.intel.com>,
Christoph Hellwig <hch@lst.de>,
Stephen Bates <Stephen.Bates@pmcs.com>
Subject: Re: [PATCH 10/15] block, dax: fix lifetime of in-kernel dax mappings
Date: Fri, 9 Oct 2015 14:12:26 -0700 [thread overview]
Message-ID: <CAPcyv4itVeM+9jkEN_wYHFWHLJEBbhm0M_L-MYOQfqJ1ta-TGw@mail.gmail.com> (raw)
In-Reply-To: <5615A31D.60800@deltatee.com>
On Wed, Oct 7, 2015 at 3:56 PM, Logan Gunthorpe <logang@deltatee.com> wrote:
> Hi Dan,
>
> We've uncovered another issue during testing with these patches. We get a
> kernel panic sometimes just while using a DAX filesystem. I've traced the
> issue back to this patch. (There's a stack trace at the end of this email.)
>
> On 22/09/15 10:42 PM, Dan Williams wrote:
>>
>> +static void dax_unmap_bh(const struct buffer_head *bh, void __pmem *addr)
>> +{
>> + struct block_device *bdev = bh->b_bdev;
>> + struct request_queue *q = bdev->bd_queue;
>> +
>> + if (IS_ERR(addr))
>> + return;
>> + blk_dax_put(q);
>> }
>>
>> @@ -127,9 +159,8 @@ static ssize_t dax_io(struct inode *inode, struct
>> iov_iter *iter,
>> if (pos == bh_max) {
>> bh->b_size = PAGE_ALIGN(end - pos);
>> bh->b_state = 0;
>> - retval = get_block(inode, block, bh,
>> - iov_iter_rw(iter) ==
>> WRITE);
>> - if (retval)
>> + rc = get_block(inode, block, bh, rw ==
>> WRITE);
>> + if (rc)
>> break;
>> if (!buffer_size_valid(bh))
>> bh->b_size = 1 << blkbits;
>> @@ -178,8 +213,9 @@ static ssize_t dax_io(struct inode *inode, struct
>> iov_iter *iter,
>>
>> if (need_wmb)
>> wmb_pmem();
>> + dax_unmap_bh(bh, kmap);
>>
>> - return (pos == start) ? retval : pos - start;
>> + return (pos == start) ? rc : pos - start;
>> }
>
>
> The problem is if get_block fails and returns an error code, it will still
> call dax_unmap_bh which tries to dereference bh->b_bdev. However, seeing
> get_block failed, that pointer is NULL. Maybe a null check in dax_unmap_bh
> would be sufficient?
Thanks for the report, I have this fixed up in v2. Will post shortly.
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next prev parent reply other threads:[~2015-10-09 21:12 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-09-23 4:41 [PATCH 00/15] get_user_pages() for " Dan Williams
2015-09-23 4:41 ` [PATCH 01/15] avr32: convert to asm-generic/memory_model.h Dan Williams
2015-09-24 15:10 ` Christoph Hellwig
2015-09-26 0:36 ` Dan Williams
2015-09-26 20:10 ` Christoph Hellwig
2015-09-28 18:44 ` Luck, Tony
2015-09-23 4:41 ` [PATCH 02/15] hugetlb: fix compile error on tile Dan Williams
2015-09-23 4:41 ` [PATCH 03/15] frv: fix compiler warning from definition of __pmd() Dan Williams
2015-09-23 4:41 ` [PATCH 04/15] x86, mm: quiet arch_add_memory() Dan Williams
2015-09-24 15:10 ` Christoph Hellwig
2015-09-23 4:41 ` [PATCH 05/15] pmem: kill memremap_pmem() Dan Williams
2015-09-24 15:11 ` Christoph Hellwig
2015-09-23 4:41 ` [PATCH 06/15] devm_memunmap: use devres_release() Dan Williams
2015-09-24 15:13 ` Christoph Hellwig
2015-09-23 4:41 ` [PATCH 07/15] devm_memremap: convert to return ERR_PTR Dan Williams
2015-09-24 15:13 ` Christoph Hellwig
2015-09-23 4:41 ` [PATCH 08/15] block, dax, pmem: reference counting infrastructure Dan Williams
2015-09-24 15:15 ` Christoph Hellwig
2015-09-25 0:03 ` Dan Williams
2015-09-25 11:32 ` Christoph Hellwig
2015-09-25 21:08 ` Williams, Dan J
2015-09-23 4:42 ` [PATCH 09/15] block, pmem: fix null pointer de-reference on shutdown, check for queue death Dan Williams
2015-09-23 4:42 ` [PATCH 10/15] block, dax: fix lifetime of in-kernel dax mappings Dan Williams
2015-10-07 22:56 ` Logan Gunthorpe
2015-10-09 21:12 ` Dan Williams [this message]
2015-09-23 4:42 ` [PATCH 11/15] mm, dax, pmem: introduce __pfn_t Dan Williams
2015-09-23 16:02 ` Dave Hansen
2015-09-23 23:36 ` Williams, Dan J
2015-09-23 4:42 ` [PATCH 12/15] mm, dax, gpu: convert vm_insert_mixed to __pfn_t, introduce _PAGE_DEVMAP Dan Williams
2015-09-23 13:47 ` Geert Uytterhoeven
2015-09-23 16:59 ` Dan Williams
2015-09-23 4:42 ` [PATCH 13/15] mm, dax: convert vmf_insert_pfn_pmd() to __pfn_t Dan Williams
2015-09-23 4:42 ` [PATCH 14/15] mm, dax, pmem: introduce {get|put}_dev_pagemap() for dax-gup Dan Williams
2015-10-02 21:21 ` Logan Gunthorpe
2015-10-02 21:53 ` Dan Williams
2015-10-02 22:14 ` Logan Gunthorpe
2015-10-02 22:42 ` Logan Gunthorpe
2015-10-02 22:55 ` Dan Williams
2015-09-23 4:42 ` [PATCH 15/15] mm, x86: get_user_pages() for dax mappings Dan Williams
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