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SubjectRe: Q: generic_file_write sets PG_locked???

On 21 Apr 1999 19:46:21 -0500, (Eric W. Biederman) said:

> As note on the PG_locked flag.
> That simply indicates that there is I/O inprocess on the page and you
> can use wait_on_page to wait for it to complete.

> This does not prevent pages from being mapped.

> If we count on PageLocked from keeping a page from being mapped in
> while it is being written out, I think that is a part of the current
> NFS design that needs to be redesigned.

Yes and no. PageLocked may just indicate a background writeback in
progress. That definitely happens in the swap cache right now, but the
vfs code doesn't use it for the page cache (yet). It will do. However,
if a given filesystem provides its own write-page strategy functions
which have their own locking semantics, there's no real reason to
prevent it from doing so as long as the page mapping functions continue
to block on a non-uptodate page.

> I'm not prepared quite yet, for a large discussion on the code as I
> haven't finished testing my prototypes. Once that is done I'll write
> up some documentation and start pushing for integration of generic
> dirty page handling for 2.3

_Good_. :)


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