Re: Re: which function writes to the disk

["Rajaram Suresh Gaunker" <rajarams1@rediffmail.com>]

hi
can i use do_generic_file_read_IO

here i have constints that only one user is using the file..

can any body tell me how to enforce these constraints ..

i've copied the ext2 file system and i am modifing it to obtaint a 
cryptographic file system,

can i just encrypt in function genric_file_write and generic_file 
write will it work

(i will change the names of this functions as many other file 
system uses the same read write functions)

rajaram



On Wed, 05 Mar 2003 Jan Harkes wrote :
>On Wed, Mar 05, 2003 at 07:25:13AM -0000, Rajaram Suresh Gaunker 
>wrote:
> > which functions writes to the disk in file system?
> >
> > how can i know which user wants to write to disk, or which 
>user
> > has called the system call?
>
>That is a little difficult, last time I looked, writes were just 
>marking
>the memory page dirty. At some point there is this kernel flush 
>daemon
>that wanders by, notices that the page is dirty and kicks off the 
>actual
>IO.
>
>In the mean time several users might have written to the same 
>page
>before IO has even started which makes it unclear which user 
>has
>permission to write. Will all valid writes fail if one user's
>permissions have expired? Or will we allow an user's writes to
>succeed just because he is piggybacking on the valid writers.
>
> > user registers his key by using a system call which i'm
> > providing he can also unregister itself using a system call
> >
> > the key for each user is stored in kernel when we are writing 
>the
> > data to file of user we will encrypt using owners key
>
>You might want to google for 'cryptfs', 'cfs', and 'tcfs'.
>
>Jan
>



R@j@r@m
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