Re: fs requirements for loop device?

[Andrew Morton <akpm@zip.com.au>]

Christoph Hellwig wrote:
> 
> On Mon, May 13, 2002 at 09:43:05AM -0500, Steve Lord wrote:
> > > ->readpage in address space operations as it uses that directly
> > > (apparently, I never looked at it).
> >
> > You need prepare_write and commit_write too.
> 
> And even worse you need locking rules similar to the generic file
> operations in mm/filemap.c, this was for example biteing GFS/OpenGFS.
> 
> In short: loop.c is a horrible mess nad usually only works for
> fileystems using generic_file_read/generic_file_write, an exceptions
> is XFS that has very similar operations to those, but due to lack of
> takeing a lock I'm still not sure whether is really is 100% correct.
> 
> An yes, I think the abuse of do_generic_file_read is a big mistake,
> it should never have been exported from filemap.c.
> 

Can anyone point at a reason why loop shouldn't use the
->read() and ->write() methods of the backing file's
file_operations?

AFAICS, that fixes everything, including tmpfs.

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