linux-kernel - Re: [PATCH 1/2] dax: fix O_DIRECT I/O to the last block of a blockdev

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Date:	Tue, 8 Sep 2015 12:10:00 -0400
From:	Linda Knippers <linda.knippers@....com>
To:	Linda Knippers <linda.knippers@...com>,
	Jeff Moyer <jmoyer@...hat.com>, matthew.r.wilcox@...el.com
Cc:	linux-fsdevel@...r.kernel.org, linux-nvdimm@...1.01.org,
	linux-kernel@...r.kernel.org,
	Ross Zwisler <ross.zwisler@...ux.intel.com>
Subject: Re: [PATCH 1/2] dax: fix O_DIRECT I/O to the last block of a blockdev

This patch and the 2/2 patch don't seem to have gone anywhere.
Willy?  or Ross?

-- ljk

On 8/14/2015 4:53 PM, Linda Knippers wrote:
> On 8/14/2015 4:15 PM, Jeff Moyer wrote:
>> commit bbab37ddc20b (block: Add support for DAX reads/writes to
>> block devices) caused a regression in mkfs.xfs.  That utility
>> sets the block size of the device to the logical block size
>> using the BLKBSZSET ioctl, and then issues a single sector read
>> from the last sector of the device.  This results in the dax_io
>> code trying to do a page-sized read from 512 bytes from the end
>> of the device.  The result is -ERANGE being returned to userspace.
>>
>> The fix is to align the block to the page size before calling
>> get_block.
>>
>> Thanks to willy for simplifying my original patch.
>>
>> Signed-off-by: Jeff Moyer <jmoyer@...hat.com>
> 
> Tested-by:  Linda Knippers <linda.knippers@...com>
> 
>> ---
>>  fs/dax.c | 3 ++-
>>  1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/fs/dax.c b/fs/dax.c
>> index a7f77e1..ef35a20 100644
>> --- a/fs/dax.c
>> +++ b/fs/dax.c
>> @@ -116,7 +116,8 @@ static ssize_t dax_io(struct inode *inode, struct iov_iter *iter,
>>  		unsigned len;
>>  		if (pos == max) {
>>  			unsigned blkbits = inode->i_blkbits;
>> -			sector_t block = pos >> blkbits;
>> +			long page = pos >> PAGE_SHIFT;
>> +			sector_t block = page << (PAGE_SHIFT - blkbits);
>>  			unsigned first = pos - (block << blkbits);
>>  			long size;
>>  
>>
> 

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