Re: [PATCH] dirty pages in memory & co.

[ebiederm+eric@ccr.net (Eric W. Biederman)]

>>>>> "ST" == Stephen C Tweedie <sct@redhat.com> writes:

ST> Hi,
ST> On 07 May 1999 09:56:00 -0500, ebiederm+eric@ccr.net (Eric W. Biederman)
ST> said:

>> It looks like I need 2 variations on generic_file_write at the
>> moment. 
>> 1) for network filesystems that can get away without filling
>> the page on a partial write.
>> 2) for block based filesystems that must fill the page on a
>> partial write because they can't write arbitrary chunks of
>> data.

ST> I'd be very worried by (1): sounds like a partial write followed by a
ST> read of the full page could show up garbage in the page cache if you do
ST> this.  If NFS skips the page clearing for partial writes, how does it
ST> avoid returning garbage later?

Actually (1) is current behaviour.  I really don't like it but I can see
how it can potentially improve performance.  Partial writes are handled
by not setting PG_uptodate.

Reads are handled by always flushing the per page dirty data before reading.

I don't especially like it but it's what we have now.

Eric
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