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From: Christoph Hellwig <hch@infradead.org>
To: Vivek Goyal <vgoyal@redhat.com>
Cc: linux-fsdevel@vger.kernel.org, linux-nvdimm@lists.01.org,
	hch@infradead.org, dm-devel@redhat.com
Subject: Re: [PATCH v3 2/7] pmem: Enable pmem_do_write() to deal with arbitrary ranges
Date: Mon, 17 Feb 2020 05:23:09 -0800
Message-ID: <20200217132309.GC14490@infradead.org> (raw)
In-Reply-To: <20200207202652.1439-3-vgoyal@redhat.com>

On Fri, Feb 07, 2020 at 03:26:47PM -0500, Vivek Goyal wrote:
> Currently pmem_do_write() is written with assumption that all I/O is
> sector aligned. Soon I want to use this function in zero_page_range()
> where range passed in does not have to be sector aligned.
> 
> Modify this function to be able to deal with an arbitrary range. Which
> is specified by pmem_off and len.
> 
> Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
> ---
>  drivers/nvdimm/pmem.c | 30 ++++++++++++++++++++++--------
>  1 file changed, 22 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
> index 9ad07cb8c9fc..281fe04d25fd 100644
> --- a/drivers/nvdimm/pmem.c
> +++ b/drivers/nvdimm/pmem.c
> @@ -154,15 +154,23 @@ static blk_status_t pmem_do_read(struct pmem_device *pmem,
>  
>  static blk_status_t pmem_do_write(struct pmem_device *pmem,
>  			struct page *page, unsigned int page_off,
> -			sector_t sector, unsigned int len)
> +			u64 pmem_off, unsigned int len)
>  {
>  	blk_status_t rc = BLK_STS_OK;
>  	bool bad_pmem = false;
> -	phys_addr_t pmem_off = sector * 512 + pmem->data_offset;
> -	void *pmem_addr = pmem->virt_addr + pmem_off;
> -
> -	if (unlikely(is_bad_pmem(&pmem->bb, sector, len)))
> -		bad_pmem = true;
> +	phys_addr_t pmem_real_off = pmem_off + pmem->data_offset;
> +	void *pmem_addr = pmem->virt_addr + pmem_real_off;
> +	sector_t sector_start, sector_end;
> +	unsigned nr_sectors;
> +
> +	sector_start = DIV_ROUND_UP(pmem_off, SECTOR_SIZE);
> +	sector_end = (pmem_off + len) >> SECTOR_SHIFT;
> +	if (sector_end > sector_start) {
> +		nr_sectors = sector_end - sector_start;
> +		if (unlikely(is_bad_pmem(&pmem->bb, sector_start,
> +					 nr_sectors << SECTOR_SHIFT)))
> +			bad_pmem = true;

I don't think an unlikely annotation makes much sense for assigning
a boolean value to a flag variable.

> +		/*
> +		 * Pass sector aligned offset and length. That seems
> +		 * to work as of now. Other finer grained alignment
> +		 * cases can be addressed later if need be.
> +		 */

This comment seems pretty scary.  What other cases can you think of?
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Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-07 20:26 [PATCH v3 0/7] dax,pmem: Provide a dax operation to zero range of memory Vivek Goyal
2020-02-07 20:26 ` [PATCH v3 1/7] pmem: Add functions for reading/writing page to/from pmem Vivek Goyal
2020-02-17 13:21   ` Christoph Hellwig
2020-02-17 18:04     ` Vivek Goyal
2020-02-07 20:26 ` [PATCH v3 2/7] pmem: Enable pmem_do_write() to deal with arbitrary ranges Vivek Goyal
2020-02-17 13:23   ` Christoph Hellwig [this message]
2020-02-17 14:59     ` Vivek Goyal
2020-02-07 20:26 ` [PATCH v3 3/7] dax, pmem: Add a dax operation zero_page_range Vivek Goyal
2020-02-17 13:26   ` Christoph Hellwig
2020-02-17 18:08     ` Vivek Goyal
2020-02-07 20:26 ` [PATCH v3 4/7] s390,dcssblk,dax: Add dax zero_page_range operation to dcssblk driver Vivek Goyal
2020-02-10 20:53   ` Gerald Schaefer
2020-02-11 15:11     ` Vivek Goyal
2020-02-11 15:49       ` Gerald Schaefer
2020-02-07 20:26 ` [PATCH v3 5/7] dm,dax: Add dax zero_page_range operation Vivek Goyal
2020-02-07 20:26 ` [PATCH v3 6/7] dax,iomap: Start using dax native zero_page_range() Vivek Goyal
2020-02-17 13:26   ` Christoph Hellwig
2020-02-07 20:26 ` [PATCH v3 7/7] dax,iomap: Add helper dax_iomap_zero() to zero a range Vivek Goyal
2020-02-17 13:27   ` Christoph Hellwig
2020-02-14 12:57 ` [PATCH v3 0/7] dax,pmem: Provide a dax operation to zero range of memory Vivek Goyal

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