Re: fs block size and PAGE_CACHE_SIZE

[David Chow <davidchow@shaolinmicro.com>]

Trond Myklebust wrote:

>>>>>>" " == David Chow <davidchow@shaolinmicro.com> writes:
>>>>>>            
>>>>>>
>
>     > How can you make sure there are no race conditions in
>     > populating multiple page caches and making them up-to-date
>     > afterwards? Since readpage only make sures you lock one page,
>
>Have a browse through mm/readahead.c (in particular read_pages() and
>read_cache_pages()).
>The page is is anonymous when it gets locked, and is only added to the
>page cache) if there is no existing page. The lock is only released by
>the filler.
>
>     > If readpages() is added for 2.5, it doesn't mean read page
>     > don't have to implement readpage(), right?
>
>Right. You still have to implement readpage.
>
So it is impossible to do under 2.4? Since all the design of VFS and 
page cache assumes the underlying fs uses a 4k page or something 
equivalent less to the size of a PAGE_CACHE_SIZE as the largest unit of 
a cache. If you read Phillip Lougher's mail which points to the squash 
fs (read-only), plus the problem of sleeping which really impossible to 
implement a read/write fs on smp systems (which I suppose to, and the 
current fs already supported). If it is impossible, I don't bother to 
think though.

regards,
David Chow

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