Re: [PATCH 1/3] Add flag to identify block swap devices

From: Hugh Dickins
Date: Mon May 17 2010 - 15:35:56 EST

On Mon, May 17, 2010 at 4:50 AM, Minchan Kim <> wrote:
> On Mon, May 17, 2010 at 2:32 PM, Nitin Gupta <ngupta@xxxxxxxxxx> wrote:
>> Added SWP_BLKDEV flag to distinguish block and regular file backed
>> swap devices. We could also check if a swap is entire block device,
>> rather than a file, by:
>> S_ISBLK(swap_info_struct->swap_file->f_mapping->host->i_mode)
>> but, I think, simply checking this flag is more convenient.
>> Signed-off-by: Nitin Gupta <ngupta@xxxxxxxxxx>
> Reviewed-by: Minchan Kim <>
> We can enhance swap_show by the flag as further patch.

You mean, make swap_show() decide partition or file by SWP_BLKDEV
instead of its own test?

Actually, I'd prefer we don't embed SWP_BLKDEV further, because it's
a bit of a hack and not really necessary. What ought to happen (though
perhaps it's silly to be expending code over an imaginary case) is a
map_swap_entry() call to convert the swap offset to physical page
within partition - no-op in the partition case, but correcting the file case.

But I wouldn't want to write that patch without testing it,
which I won't be doing for a while.

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