Re: kiobuf using kernel pages

Keith Owens (kaos@ocs.com.au)
Sat, 13 Nov 1999 02:04:48 +1100

On Fri, 12 Nov 1999 14:33:52 +0000 (GMT),
"Stephen C. Tweedie" <sct@redhat.com> wrote:
>On Fri, 12 Nov 1999 16:30:23 +1100, Keith Owens <kaos@ocs.com.au>
>said:
>> User I/O: sys_write->sd_raw_fops.write->sd_raw_write->sd_raw_rw
>> Kernel I/O: vmdump->sd_raw_fops.write->sd_raw_write->sd_raw_rw
>
>That's the wrong way to do it.
>
>We need a new file_operations entry, rw_kiovec. So it looks like
>
> sys_write->block_rw_kiovec->sd_raw_write->sd_raw_rw
>and vmdump->make_dump_kiovec->sd_raw_write->sd_raw_rw
>
>The kiobuf management should _all_ be done at the level where we are
>originating the block IO, not in the per-device operations.

Do we want to add yet another file operation entry? Especially when
the *only* different between the two cases is whether to use user or
kenrel mappings. I added FMODE_KERNBUF to the filp mode flags, normal
code does not set this flag, vmdump sets it when creating its dump
filp. sd_raw_write looks at that flag and maps the kiobuf accordingly.

We already use the f_mode flags to decide if we are doing read or
write. Adding another flag for user vs. kernel seems the smallest
change and is compatible with the current usage of f_mode.

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