Re: How does ramfs actually fills the page cache with data?

[Ho Chak Hung]

thanks a lot for your reply

But is it at all possible to put data into page cache without going through the inodes or files? I mean, for example, if you are given a string "abcde", and you want to allocate a page to store this "abcde" into that page and add that page to the page cache, what would you do? 

2)The ramfs uses the generic file operation
Ingo Oeser <[e-mail]> wrote:
>
> On Fri, Jun 22, 2001 at 05:45:27PM -0400, Ho Chak Hung wrote:
> > In fs/ramfs/inode.c, how does ramfs actually fills the page
> > cache with data? In the readpage operation, it only zero-fill
> > the page if it didn't already exist in the page cache. However,
> > how do I actually fill the page with data?
> 
> The page cache does it itself. 
> 
> "readpage" is to move pages from the backing store into the page
> cache. 
> 
> "writepage" and friends is for updating the backing store with
> the contents of the page cache.
> 
> There is no real backing store of ramfs, since ramfs data lives
> completly in page cache. 
> 
> But we cannot give the user random memory contents, so we zero it
> out on readpage and prepare_write.
> 
> The data is copied with copy_{from,to}_user in the generic file
> operations (look how ramfs_file_operations is defined and look at
> the functions referenced), which read/write through page cache.
> 
> Regards
> 
> Ingo Oeser
> -- 
> Use ReiserFS to get a faster fsck and Ext2 to fsck slowly and gently.
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