Re: page flags ?

[Badari Pulavarty <pbadari@us.ibm.com>]

On Wed, 2005-05-18 at 14:56, Andrew Morton wrote:
> Badari Pulavarty <pbadari@us.ibm.com> wrote:
> >
> > Does anyone know what this page-flag is used for ? I see some
> > references to this in AFS. 
> > 
> > Is it possible for me to use this for my own use in ext3 ? 
> > (like delayed allocations ?) Any generic routines/VM stuff
> > expects me to use this only for a specific purpose ?
> > 
> > #define PG_fs_misc               9      /* Filesystem specific bit */
> > 
> 
> It's identical to PG_checked, added by David Howells'
> provide-a-filesystem-specific-syncable-page-bit.patch
> 
> IIRC we decided to expand the definition of PG_checked to mean
> "a_ops-private, fs-defined page flag".  I guess if/when that patch is
> merged we'll do a kernel-wide s/PG_checked/PG_fs_misc/.
> 
> And ext3 is already using that flag.

:(

Is it possible to get yet another PG_fs_specific flag ? 
Reasons for it are:

	- I need this for supporting delayed allocation on ext3. Me, Ted
	  and Suparna thought about it for a while to see we can 
	  workaround it. So far, I haven't found a clean way.

	- useful for other folks currently overloading page->private
	  for this purpose. May be then, we can make most filesystems
	  use mpage routines (since they assume page->private is for
	  bufferheads ?)

Thanks,
Badari


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